Fermentation Control in Baker’s Yeast Production: Mapping Patents Pierre G´ elinas Abstract: During baker’s yeast manufacturing, the fermentation process must be thoroughly controlled. This review of the patent literature provides new information on the early development of industrial fermentation processes. As shown by a review of 199 patents filed between 1900 and 2009, inventors in this field were mainly interested to improve yeast yields through the control of infection and sugar concentration in the growth media. Contrary to common belief, much attention was also given to continuous culture processes, involving addition and withdrawal of growth media. These technologies were mainly developed in about 30 y, between 1910 and 1939. In the recent years, inventors gave sustained attention to the fine tuning of fermentation control, mainly the rapid determination of yeast fermentation by-products in the exhaust to get rapid feedback on the rate of sugar addition in the fermentation tank. Improved fermentation control benefited much the baking industry because baker’s yeast had higher gassing power and was cheaper. However, some of these key patents on baker’s yeast technology were later declared invalid in court because it had little intellectual property value. In the baker’s yeast trade and other sectors, this situation might have encouraged trade secrets while reducing the credibility of innovative ideas disclosed in the patent literature. Keywords: baker’s yeast, bread, fermentation control, patents, sugar Introduction Baker’s yeast production is one of the oldest food biotechnolo- gies and may be considered as a “ripened technology.” At the turn of the 20th century, the baker’s yeast industry had developed independently from distilleries where high alcohol yield gave lit- tle yeast biomass. During the golden age of modern baker’s yeast manufacturing, from 1910 to 1940, much effort was put in to find the best and cheapest growth media available (G´ elinas 2012). In addition, much interest was given to the control of both infection and sugar concentration in such sugar-rich growth media to in- crease biomass yields and reduce costs. However, little information has been published on the development of these critical aspects of baker’s yeast manufacturing. Part of this situation may be at- tributed to the fact that much technical information is disclosed in trade secrets. The objective of baker’s yeast manufacturing is to harvest as fast as possible the highest amount of living cell mass at the lowest cost. First, fermentation tanks must be seeded with the strongest and purest microbial starters, otherwise unwanted microorganisms will be harvested instead; both the gassing power and the keep- ing properties of the concentrated yeast biomass will be reduced. Second, such microorganisms must be fed under thoroughly con- trolled conditions to optimize yeast biomass and gassing power, MS 20140954 Submitted 6/2/2014, Accepted 6/18/2014. Author is with the Food Research and Development Centre, Agriculture and Agri-Food Canada, Saint- Hyacinthe, Quebec, Canada J2 8E3. Direct inquiries to author G´ elinas (E-mail: [email protected]). enough to raise dough, otherwise bakers will experience varia- tions in bread volume. Major steps of baker’s yeast manufacturing, including fermentation control, have been described in G´ elinas (2006). Searching the patent literature is an original way to follow the evolution of specific technologies. This study is a follow-up and companion to reviews of the early patent literature from the 19th century (G´ elinas 2010a), growth media (G´ elinas 2012), strains and specialty ingredients (G´ elinas 2009), and yeast management at the bakery plant (G´ elinas 2010b). In addition, this study provides some insight on the true value of patenting activity. For example, prob- lems with double-patenting have been stressed in a companion paper (G´ elinas 2012). This review suggests that, although they had previously been accepted by patent examiners, key patents on fer- mentation control in baker’s yeast production were judged invalid in justice courts for want of invention. The objective of this review was to study the evolution of fer- mentation control for baker’s yeast production based on patenting activity. The main objective of such fermentation control was to improve yield and reduce the cost of commercial baker’s yeast. These technologies were instrumental to the large-scale manufac- turing of high-quality bread. Patents Background information and search criteria This review is based on the concept of patent families, which combines closely related patented inventions granted be- tween 1900 and 2009 (G´ elinas 2012). In addition to granted patents, specifications of 5 nonaccepted patents were found and C 2014 Her Majesty the Queen in Right of Canada Journal of Food Science C 2014 Institute of Food Technologists ® Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada. doi: 10.1111/1541-4337.12107 Vol. 13, 2014 Comprehensive Reviews in Food Science and Food Safety 1141
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Fermentation Control in Baker’s Yeast Production:Mapping PatentsPierre Gelinas
Abstract: During baker’s yeast manufacturing, the fermentation process must be thoroughly controlled. This review ofthe patent literature provides new information on the early development of industrial fermentation processes. As shownby a review of 199 patents filed between 1900 and 2009, inventors in this field were mainly interested to improve yeastyields through the control of infection and sugar concentration in the growth media. Contrary to common belief, muchattention was also given to continuous culture processes, involving addition and withdrawal of growth media. Thesetechnologies were mainly developed in about 30 y, between 1910 and 1939. In the recent years, inventors gave sustainedattention to the fine tuning of fermentation control, mainly the rapid determination of yeast fermentation by-products inthe exhaust to get rapid feedback on the rate of sugar addition in the fermentation tank. Improved fermentation controlbenefited much the baking industry because baker’s yeast had higher gassing power and was cheaper. However, some ofthese key patents on baker’s yeast technology were later declared invalid in court because it had little intellectual propertyvalue. In the baker’s yeast trade and other sectors, this situation might have encouraged trade secrets while reducing thecredibility of innovative ideas disclosed in the patent literature.
IntroductionBaker’s yeast production is one of the oldest food biotechnolo-
gies and may be considered as a “ripened technology.” At theturn of the 20th century, the baker’s yeast industry had developedindependently from distilleries where high alcohol yield gave lit-tle yeast biomass. During the golden age of modern baker’s yeastmanufacturing, from 1910 to 1940, much effort was put in to findthe best and cheapest growth media available (Gelinas 2012). Inaddition, much interest was given to the control of both infectionand sugar concentration in such sugar-rich growth media to in-crease biomass yields and reduce costs. However, little informationhas been published on the development of these critical aspectsof baker’s yeast manufacturing. Part of this situation may be at-tributed to the fact that much technical information is disclosedin trade secrets.
The objective of baker’s yeast manufacturing is to harvest as fastas possible the highest amount of living cell mass at the lowestcost. First, fermentation tanks must be seeded with the strongestand purest microbial starters, otherwise unwanted microorganismswill be harvested instead; both the gassing power and the keep-ing properties of the concentrated yeast biomass will be reduced.Second, such microorganisms must be fed under thoroughly con-trolled conditions to optimize yeast biomass and gassing power,
MS 20140954 Submitted 6/2/2014, Accepted 6/18/2014. Author is with theFood Research and Development Centre, Agriculture and Agri-Food Canada, Saint-Hyacinthe, Quebec, Canada J2 8E3. Direct inquiries to author Gelinas (E-mail:[email protected]).
enough to raise dough, otherwise bakers will experience varia-tions in bread volume. Major steps of baker’s yeast manufacturing,including fermentation control, have been described in Gelinas(2006).
Searching the patent literature is an original way to follow theevolution of specific technologies. This study is a follow-up andcompanion to reviews of the early patent literature from the 19thcentury (Gelinas 2010a), growth media (Gelinas 2012), strains andspecialty ingredients (Gelinas 2009), and yeast management at thebakery plant (Gelinas 2010b). In addition, this study provides someinsight on the true value of patenting activity. For example, prob-lems with double-patenting have been stressed in a companionpaper (Gelinas 2012). This review suggests that, although they hadpreviously been accepted by patent examiners, key patents on fer-mentation control in baker’s yeast production were judged invalidin justice courts for want of invention.
The objective of this review was to study the evolution of fer-mentation control for baker’s yeast production based on patentingactivity. The main objective of such fermentation control was toimprove yield and reduce the cost of commercial baker’s yeast.These technologies were instrumental to the large-scale manufac-turing of high-quality bread.
PatentsBackground information and search criteria
This review is based on the concept of patent families,which combines closely related patented inventions granted be-tween 1900 and 2009 (Gelinas 2012). In addition to grantedpatents, specifications of 5 nonaccepted patents were found and
Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.
doi: 10.1111/1541-4337.12107 Vol. 13, 2014 � Comprehensive Reviews in Food Science and Food Safety 1141
Fermentation control and baker’s yeast . . .
cited: GB 191007640; GB 191023662; GB 191417009;GB146947; GB 230050. For those not familiar with the patent lit-erature, letter codes correspond to the country where patents werefiled; in the case cited above, patents filed in Great Britain with anapplication date earlier than 1916 had numbers that included theyear of application and the serial number.
For the sake of clarity and simplicity, patents are presented ac-cording to the “priority date.” This corresponds to the filing dateexcept for German patents where the priority date in the publica-tion (“Patentiert vom”) was 1 d later than the “convention date”(filing date) cited in foreign patents. Further details on patents andsearch criteria may be found in Gelinas (2010a, 2012).
Evolution of Patenting Activity According to YearNumber of patents
Table 1 presents the evolution in the number of patent appli-cations filed on the control of fermentation during baker’s yeastproduction. Overall, 225 patents were found, including 26 filedbefore the year 1900 as reported in Gelinas (2010a).
The most important patenting activity was on the control ofsugar concentration in growth media, with 52 patents. That num-ber does not include 38 patents on related inventions on addition-withdrawing of growth media, also called “continuous culture.”Interest of the inventors was similar for seed production and in-fection control during fed-batch fermentation, respectively, with38 and 36 patents. To a lesser extent, some interest was given tonitrogen concentration (26 patents), final conditioning steps (23patents), and temperature control (12 patents).
Compared to patents on growth media for baker’s yeast (Gelinas2012), interest in the control of fermentation parameters camelater, around 1910 rather than 1875; it also lasted for 30 y (1910to 1939) instead of about 70 y (1875 to 1944). For both sub-jects, there was a major drop of patenting activity after 1939. Thisconfirms that selection of growth media and fermentation controlfor baker’s yeast were ripened technologies around that period,enough to be commercially viable for supplying the large-scalebaking industry. This might have been partly caused by the begin-ning of World War II (1939 to 1945) in Europe, although WorldWar I (1914 to 1918) did not appear to have a major negativeeffect on patenting activity (Table 1). As discussed later, there isa possibility that lawsuits dismissing key patents in baker’s yeasttechnology discouraged patent filing in this sector. After 1940, in-ventors showed some interest in the control of sugar concentrationthrough ethanol analyses and, to a lesser extent, infection controland conditioning.
InventorsCountry of origin
Table 2 indicates that German inventors were the most activewith 53 patents, although this number did not include 8 patentapplications by citizens from the German Democratic Republicfiled between 1950 and 1990. These trends confirm those seen foryeast growth media (Gelinas 2012). For both topics (media andfermentation control), patenting activity from Germany peakedaround 1930 to 1934. As was the case for patents on yeast growthmedia (Gelinas 2012), German inventors filed patents in foreigncountries, contrary to U.S. inventors that rarely protected inven-tions outside their own country (data not shown). With 50 patents,or about as many as German inventors, citizens from the UnitedStates and, in particular from the Fleischmann/Standard Brandsgroup, were also very active inventors on fermentation control forbaker’s yeast and their peak activity was around 1925 and 1934.
Except for citizens from Germany and the United States, themost active inventors on fermentation control in baker’s yeastproduction came from France, Japan, Great Britain, Denmark,and Austria. However, among the latter, only Japanese inventorsappeared to show a more recent interest in these technologies, es-pecially those related to the control of sugar concentration duringfermentation.
CompaniesAbout one-half of the patents on yeast fermentation control
were owned by companies or research institutes. This representsa higher proportion than for growth media (about 35%), whichconfirms the economical importance of this subject. Overall, 62companies were interested in getting intellectual property rightson fermentation control for baker’s yeast production. However,according to Table 3, only 12 companies had more than 3 patents,which is about the same as growth media (Gelinas 2012). Thissuggests that the development of both growth media and fermen-tation control was of interest to only a handful of manufacturersthat took control of those topics in the early years of the develop-ment of modern baker’s yeast manufacturing.
As for growth media, the Fleischmann/Standard Brands groupwas the most active with not less than 17 patents on fermentationcontrol. This does not include 3 patents held by the Interna-tional Yeast Co., based in London, and 1 patent filed in 1984by Nabisco Brands, Inc., these companies also being affiliatedwith the same group. As described later, 16 more patents by theFleischmann/Standard Brands group were also obtained under li-cense agreements with various inventors from Europe, includinga German research institute, Verein der Spiritus-Fabrikanten inDeutschland.
LicensesWhen searching the patent literature, it may be difficult to de-
termine inventorship. Especially before 1950, some patents werefiled under different names in different countries (Gelinas 2012). Insome cases, it may be very difficult to trace back the true inventor,the one who was the first to file in patent offices the specifica-tions describing the invention. Some inventions were assigned todifferent applicants, probably in exchange of money, which corre-sponded much to a license. Thorough reading of patent claims isessential to determine or distinguish inventorship from licensees.
According to Table 4, 24 basic patents produced 28 licenseson fermentation control, which is similar to the 21 licenses ongrowth media (Gelinas 2012). In general, most of the licenseswere negotiated between established companies, except in a fewcases where individuals appeared to have sold the rights of their in-ventions. Contrary to patents on growth media where 10 obscurelicense cases were found (no proper citation of the basic patent),no double-patenting situation was found, so each patent specifica-tion corresponded to a license that properly cited the priority file,the first to describe the basic invention. The industrial group con-sisting of The Fleischmann Co. and Standard Brands Inc. (U.S.A.)had the largest share of such licenses (16 over 28) and, around thatperiod, also owned the rights for 3 more patented inventions thatwere licensed to The International Yeast Co. Ltd (Great Britain).Vereinigte Mautner’sche Presshefe-Fabriken G.m.b.H. (Austria)had 4 licenses. For growth media applications, the companies fromthe United States and Austria, respectively, had 5 and 1 licenses(Gelinas 2012).
Table 4 shows that most of the licenses were on the con-trol of sugar concentration as part of the continuous process
Table 1–Categories of patents on fermentation control in baker’s yeast production according to filing date.a
Year Seed Infection Temperature Sugar Continuous culture Nitrogen Conditioning Total
1870 to 1874 1 11875 to 1879 1 1 1 31880 to 1884 1 11885 to 1889 3 3 1 71890 to 1894 2 1 2 51895 to 1899 5 3 1 91900 to 1904 2 5 1 81905 to 1909 1 2 1 2 61910 to 1914 4 3 1 1 3 1 131915 to 1919 3 3 1 6 2 4 1 201920 to 1924 2 3 2 6 2 151925 to 1929 1 2 2 6 9 6 3 291930 to 1934 3 1 3 5 6 3 2 231935 to 1939 1 1 1 3 2 2 1 111940 to 1944 2 1 2 1 61945 to 1949 2 1 3 1 71950 to 1954 1 2 2 1 61955 to 1959 1 3 1 3 81960 to 1964 1 1 1 31965 to 1969 1 1 2 1 51970 to 1974 2 1 1 41975 to 1979 1 2 1 41980 to 1984 1 6 2 1 101985 to 1989 1 1 2 1 51990 to 1994 4 41995 to 1999 1 1 3 52000 to 2004 3 1 42005 to 2009 1 1 1 3Subtotal (before 1900) 10 8 1 3 0 0 4 26Subtotal (1900 to 2009) 28 28 11 49 38 26 19 199Total 38 36 12 52 38 26 23 225aPatents prepared by the same inventor and representing variations or improvements of the same invention were combined into a single patent for invention. Information on patents filed before 1900 wasadapted from Gelinas (2010a).
Table 2–Country of origin of inventors on fermentation control in baker’s yeast production according to filing date of patents.
Year DE US FR JP GB DK AT DD CS BE HU NL SE RU Others Total
Before 1900a 6 4 5 3 3 1 3 1 261900 to 1904 3 3 1 1 81905 to 1909 3 2 1 61910 to 1914 3 2 1 2 3 1 RO 131915 to 1919 6 5 2 2 2 1 1 CH 201920 to 1924 2 5 1 1 5 AU 151925 to 1929 5 11 1 1 4 3 1 1 1 YU 291930 to 1934 10 8 2 2 1 231935 to 1939 2 5 2 1 AU 111940 to 1944 4 1 1 61945 to 1949 3 1 1 2 71950 to 1954 1 1 2 1 1 61955 to 1959 1 3 3 1 81960 to 1964 1 1 1 31965 to 1969 1 1 1 2 51970 to 1974 1 1 1 1 41975 to 1979 4 41980 to 1984 2 5 3 101985 to 1989 1 2 1 1 51990 to 1994 1 2 1 41995 to 1999 1 1 1 1 IE 52000 to 2004 1 1 1 1 42005 to 2009 1 2 3Total 53 50 23 17 16 15 14 8 6 4 4 4 3 2 6 225aThese data were partly adapted from Gelinas (2010a).Based on Recommended Standards of the World Intellectual Property, the following 2-letter codes for the representation of States have been used for patent numbers and country of origin of inventors: AT,Austria; AU, Australia; BE, Belgium; CH, Switzerland; CS, Czechoslovakia; DD, German Democratic Republic; DE, Germany; DK, Denmark; FR, France; GB, Great Britain; HU, Hungary; IE, Ireland; JP, Japan; NL,Netherlands; RO, Romania; RU, Russia; SE, Sweden; US, United States of America; YU, Yugoslavia. For patents with inventors from different countries, only the country of the 1st inventor was considered.
(8) or not (9); to a lesser extent, some interest for licenses wasseen for nitrogen control (4), seed production (3), infection con-trol (2), and temperature control (2). This is also a clear indi-cation of the importance that the yeast industry gave to thesematters.
With Friedrich Hayduck (1880 to 1961) as the inventor, Vereinder Spiritus-Fabrikanten in Deutschland (Berlin, Germany) wasthe most active group to license; these 5 applications were filedon the same day (October 30, 1920) and assigned only in the
United States and Canada to The Fleischmann Co. For fermen-tation control during baker’s yeast production, licenses were filedbetween 1919 and 1947 (with peaks between 1919 to 1920 and1932 to 1935) from patented inventions originally filed between1915 and 1943. This confirms that, over 30 y, improvements ofthe control of fermentation were major concerns for the industry,which corresponds to the golden age of modern yeast technologythat truly began in 1910 to 1915 and ended around 1947, shortlyafter World War II.
Akademie der Wissenschaften der DDR (Berlin, Deutsche Democratic Republic) Infection (1984); sugar (1984, 1985); continuous culture (1983)Aktieselskabet Dansk Gaerings-Industri (Copenhagen, Denmark); Aktieselskabet
de Danske SpritfabrikkerSugar (1919; 1919; 1946; 1954); continuous culture (1936; 1947)
Kanegafuchi Chemical Ind. (Osaka, Japan); Kanegafuchi Kagaku Kogyo KabushikiKaisha
Rheinischer Actien-Verein fur Zuckerfabrikation; see Pfeifer & Langen Akt.-Ges.Standard Brands Inc. (Dover, Del., USA); see also The Fleischmann Co.; does not
include 1 patent in 1984 by Nabisco Brands, Inc. on continuous cultureSeed production (1932); temperature (1926); continuous culture
The Fleischmann Co. (New York, U.S.A.); see also Standard Brands Inc. Continuous culture (1924; 1924; 1925); nitrogen (1919; 1919);conditioning (1925)
The International Yeast Co. Ltd. (London, England) Temperature (1938); nitrogen (1938); continuous culture (1927)Verein der Spiritus-Fabrikanten in Deutschland (Berlin, Germany) Seed production (1915); infection (1900; 1915); sugar (1915);
continuous culture (1915), nitrogen (1915)Wirtschaftliche Vereinigung der Deutschen Hefeindustrie (Berlin, Germany) Continuous culture (1930; 1932; 1932)
Disputing Validity of PatentsContrary to growth media for which infringement of patents
appeared to be less important or more difficult to spot, there weremajor suits in justice courts to truly protect patented inventionson the control of fermentation during baker’s yeast manufacturing.Again, this is an indication to the commercial importance of thismatter for the baker’s yeast industry in the United States.
Table 5 (left column) shows a list of 7 patents on fermentationcontrol during baker’s yeast manufacturing that have been con-tested in courts of the United States. In 1923, when they weregranted, most of these patents were recognized as critical issues inthe development of modern yeast manufacturing, because it wasconsidered that these inventions improved much the yield, cost,and overall quality of the baker’s yeast. During that period, thelatter patented “inventions” appeared to have found major andwidespread applications in the industry, leading to infringementsof the owner’s rights.
Between 1925 and 1930, the first cases were held in court tocontest the validity of 5 patents owned by The Fleischmann Co.,which became Standard Brands Inc. in 1929. These patents werelicenses of German patents originally filed in 1915 by FriedrichHayduck. The defendant was Federal Yeast Corp. (Baltimore,Md.). In courts of the State of Maryland, all 5 patents were con-sidered valid and 4 of them were judged infringed. Costs wereestablished at $92,000 for events between October 1923 and July1926. In a court judgment on U.S. patent 1449103 (District CourtMaryland 1930a), it was estimated that, between 1923 and 1926,The Fleischmann Co. dominated the yeast industry in the UnitedStates with 11 manufacturing plants producing not less than 90%of the yeast consumed in the United States or about 1000 millionspounds annually. Producing about 9 to 12 million pounds of yeastannually, one of the biggest competitors of The Fleischmann Co.was The Liberty Co., which was acquired in 1925 by the former.One of the manufacturers sued by The Fleischmann Co. was TheFederal Yeast Corp., which produced less than 1 million poundsannually. These smaller yeast manufacturers sold yeast at a lowerprice than The Fleischmann Co., 18 to 22 cents compared to 25to 28 cents a pound, respectively.
However, between 1937 and 1939, these court decisions weredismissed in later cases involving Standard Brands Inc. and anothercompany, National Grain Yeast Corp. Now judged in the Stateof New Jersey, the issues involved 3 of the patents previouslyjudged valid in the State of Maryland (US 1449103, 1449105,and 1449106) and 2 other patents (US 1449109 and 1673735).Finally, all these patents were ruled as invalid by the judge. Inaddition, the rights for the first 3 patents were invalidated bythe U.S. Supreme Court. In essence, most of these patents wereinvalidated because of lack of invention due to similarities with aGerman patent, DE 10135, filed in 1879 by Jacques Rainer. Thelatter described a technique to feed progressively yeast starters withnutrient solutions (Gelinas 2010a).
Based on the 7 court case decisions, inventors experienced ma-jor difficulties to protect the intellectual property of key patentsin baker’s yeast technology. Despite the commercial importanceof patents under litigation, very few “inventions” were truly newand patentable. After the negative judgment by the U.S. SupremeCourt on the value of these major patents, baker’s yeast man-ufacturers saw less benefit in patent protection and some mighthave preferred not to disclose publicly their inventions. After 1939,there was a major drop in patenting activity on baker’s yeast manu-facturing in general and also by the Fleischmann/Standard Brandsgroup. Overall, this industrial group filed 49 patents in the UnitedStates on baker’s yeast growth media (Gelinas 2012) and fermen-tation control: 27 inventions + 22 licenses. As shown in Fig-ure 1, most of these patents were filed between 1915 and 1939; in1896, Charles Fleischmann himself also obtained 1 license (Gelinas2010a). It is likely that, after the judgment by the U.S. SupremeCourt in 1939, the above dismissed court cases discouraged Stan-dard Brands, and possibly others also, to patent-protect their newideas because their true novelty aspects might be too difficult toprove.
Criteria for judging novelty aspects were higher for judges ofcourts than patent examiners, who certainly questioned the truevalue of patents and stressed the limits and potential deficiencies ofthe reviewing process of patent applications. This situation high-lights the care required when drafting patent specifications that
Table 4–Cases of licenses (1900 to 2009) in which several patent applicants claimed the same invention on fermentation control in baker’s yeastproduction, with proper citation of the priority file.a
Priority date Inventor or first to file; patent nr. Licensee; patent nr. Subject
January 16,1915
Wohl and Scherdel; DE 310580 (and otherpatents)
The Fleischmann Co.; US 1475215; filed August 31, 1921 Nitrogenconcentration
February 25,March 16,March 20,April 16,and April24, 1915
Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 300663; DE 303251; DE303222; DE 304242; DE 304243; andother FR and GB versions
The Fleischmann Co.; US 1449102(CA 221756); US1449103, invalid (CA 238175); US 1449106, invalid (CA238178); US 1449110 (CA 238179); US 1449109,invalid (CA 238180); filed October 30, 1920
Nitrogenconcentration
March 17,1915
Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 300662 (GB 155284)
The Fleischmann Co.; US 1449105, invalid; CA 238172;filed October 30, 1920
Sugar concentration
April 1 and 13,1915
Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 303221; DE 304241
The Fleischmann Co.; US 1449107 (CA 238173); US1449108 (CA 238174); filed October 30, 1920
Continuous culture
May 8, 1915 Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 303253 (GB 155288)
The Fleischmann Co.; US 1449112; CA 238181; filedOctober 30, 1920
Infection control
December 24,1915
Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 303311 (FR 520523)
The Fleischmann Co.; US 1449111; US 15716, Reissue; CA238181; filed October 30, 1920
Seed production
July 5, 1919 Sak; Aktieselskabet Dansk Gaerings-Industri;DK 28507(GB 153667; FR 515704; CH90954; FI 8842; CA 215671)
#1. Vereinigte Mautner’sche Presshefe-FabrikenGesellschaft m.b.H., and Eugene Fould-Springer; AT102274; AT 105785; filed September 20, 1919
Sugar concentration
#2. The Fleischmann Co.; US 1566431; CA 237963; filedDecember 14, 1920
July 15, 1919 Aktieselskabet Dansk Gaerings-Industri; NO39412 (SE 56428; FR 503808; CH 94210;NL 8737; GB146947, not accepted; AT
#1. Vereinigte Mautner’sche Presshefe-FabrikenGesellschaft m.b.H., and Eugene Fould-Springer; AT105784; filed September 20, 1919
Sugar concentration
105784; CA 209947); FR 503810 (CH94210; CA 209948)
#2. The Fleischmann Co.; CA 237961; CA 237962; filingdate unknown
July 28, 1931 Daranyi; Invention Gesellschaft furVerwaltung und VerwertungChemischtechnischer Patente G.m.b.H.; GB376038
#1. Jointly licensed to: (1) Vereinigte Mautner Markhof’schePresshefe Fabriken und Aktien-Gesellschaft Ignaz Kuffner& Jacob Kuffner fur Brauerei, Spiritus-undPresshefefabrikation Ottakring-Dobling (Vienna), (2)Erste Ober-Osterreichische Spiritus- & PresshefefabrikJosef Kirchmeir & Sohn (Urfahr-Linz), and (3) BruderReininghaus Aktien-Gesellschaft fur Brauerei undSpiritus-Industrie (Graz-Steinfeld); AT 145684; filed July28, 1932
Continuous culture
#2. Moskovits; DE 659951; filed July 29, 1932January 26,
1932Kirby and Frey; Standard Brands Inc.; US
2029572The International Yeast Co. Limited; GB 390114; filed
December 20, 1932Seed production
March 11,1932
Wirtschaftliche Vereinigung der DeutschenHefeindustrie; DE 618021
Aktien-Gesellschaft Ignaz Kuffner & Jacob Kuffner furBrauerei, Spiritus- und PresshefefabrikationOttakring-Dobling, Aktiengesellschaft fur Spiritus- undPresshefe-Industrie Wolfrum, M. Fischl’s Sohne, andVereinigte Mautner Markhof’sche Presshefe Fabriken; AT141399; filed March 10, 1933
Continuous culture
March 3, 1933 Stich; GB 411611 Standard Brands Inc.; CA 371677; filing date unknown Sugar concentrationMarch 10,
1933Knappe (1937); DE 614753 Brandstrup (from Norway); DK 51473; filed March 8, 1934 Temperature
November23,1934
Effront and Popper; FR 794359 Standard Brands Inc.; US 2083598; filed November 23, 1935 Seed production
February 9,1938
Meyer; The International Yeast Co. Limited;GB 502762
Standard Brands Inc.; US 2214028; filed February 3, 1939 Nitrogenconcentration
December 22,1938
Meyer and Chaffe; The International YeastCo. Limited; GB 523019
Standard Brands Inc.; US 2304471; filed December 8, 1939 Temperature
February 5,1943
Berkel; DE 767347 Aktiengesellschaft Jungbunzlauer Spiritus- und ChemischeFabrik; AT 164248; filed June 10, 1947
Sugar concentration
aWhen identical versions of the same “basic patent” were issued in several countries, patent numbers are given in parentheses and without reference to the publication year. Identification of the country codes isgiven in Table 2.
Table 5–Patents on fermentation control in baker’s yeast production owned by The Fleischmann Co. or Standard Brands Inc., and contested in U.S.justice courts.
US 1449103; Hayduck (1923); nitrogen concentration; Case #1; May 9, 1925 Valid and infringedif excessive acidity is neutralized with inorganic Case #2 (Appeal); June 8, Valid and infringed; if other workers had known Hayduckammonium salts and others, yeast grows faster in an 1926 process, they would have made prompt use of itall-sugar medium such as molasses and others, and its Case #3. February 10, 1930 Valid and infringed; damages were set at $92,000quality is improved (fermentation power and keeping Case #5. October 29, 1937 Valid and infringed only for the specific use of aquaproperties) ammonia (not ammonium lactate and di-ammonium
phosphate)Case #6 (Appeal); February 1,
1939Invalid for want of invention over the prior art; it was
known that yeast growth was stimulated byneutralizing the deleterious effect of acid by antacid;this old principle was applied to yeast manufacturing
Case #7 (Supreme Court);November 6, 1939
Invalid for want of invention over the prior art;neutralization of acids was the application of an oldprinciple with no change in the manner of application
US 1449127; Nilsson and Harrison (1923); nitrogen Case #1; May 9, 1925 Invalid because claims are equivalent to US 1449103concentration; aqua ammonia may be used to described aboveneutralize excessive acidity in combination with Case #2 (Appeal); June 8, Valid and infringedammonium phosphate (nutrient) 1926
US 1449102; Hayduck (1923); nitrogen concentration;excessive acidity is controlled with dilution ratherthan neutralization described in US 1449103
Case #4; February 10, 1930 Valid but not infringed
US 1449105; Hayduck (1923); sugar concentration; Case #4; February 10, 1930 Valid and infringed, despite similarities with a patentdilute medium is slowly supplemented with medium of filed in 1879 by Rainerhigher concentration Case #5; October 29, 1937 Invalid because claims are indefinite, vague, and
uncertainCase #6 (Appeal); February 1,
1939Invalid because claims are too vague and indefinite; it is
a mechanical improvement over the prior art mainlydescribed in 1879 by Rainer because it does notascertain the times and manner in which theconcentrated nutrient solution is to be added
Case #7 (Supreme Court);November 6, 1939
Invalid for want of sufficient disclosure (too vague andindefinite); regulated rate of feeding is no more than amechanical improvement over the prior art
US 1449106; Hayduck (1923); sugar concentration; Case #4; February 10, 1930 Valid and infringedcombines disclosures of US 1449103 (neutralization) Case #5; October 29, 1937 Invalid for want of invention over the prior art and basedand US 1449105 (dilution) on US 1449105 which is invalid
Case #6 (Appeal); February 1,1939
Invalid for want of invention and based on US 1449103and US 1449105 which are invalid
Case #7 (Supreme Court);November 6, 1939
Invalid for want of novelty; process is the combination ofUS 1449103 and US 1449105 which are invalid
US 1449109; Hayduck (1923); nitrogen concentration; Case #5; October 29, 1937 Invalid for want of invention compared to US 1449103acid is neutralized with ammonium sulfate Case #6 (Appeal); February 1, Invalid for want of invention; ammonium salts have been
1939 mentioned in other patentsUS 1673735; Corby and Buhrig (1928); sugar Case #5; October 29, 1937 Invalid for want of novelty
concentration; similar to US 1449105 and US Case #6 (Appeal); February 1, Invalid for want of novelty compared to US 14491051449106 except that portion of the growth medium 1939 and 1449106is withdrawn during propagation
aFor sake of clarity, justice court cases are cited as follows:Case #1. District Court of Maryland (1925);Case #2. Circuit Court of Appeals (1926);Case #3. District Court of Maryland (1930a);Case #4. District Court of Maryland (1930b);Case #5. District Court of New Jersey (1937);Case #6. Circuit Court of Appeals (1939);Case #7. U.S. Supreme Court (1939).
truly show novelty aspects compared to prior art (Roberts 2007;Ohly 2008).
In conclusion, drop of patenting activity by the most active in-dustrial in the baker’s yeast industry between 1920 and 1940 mightreflect the artisanal nature of this industry around that period. Didnegative justice court decisions discourage this manufacturer andothers to protect their innovative ideas through patents? This wascertainly not an encouragement to privilege patent filing withcomplete written disclosure of their innovative ideas. In all casesdismissed in justice courts of the United States, patents under liti-gation were not developed by the company but they were ratherlicensed from original German inventions. According to Khan(2005), such rudimentary innovations might be better protectedby trade secrets, as was the case for chocolate composition orproduction. This appeared to be the case for fermentation controlin baker’s yeast production, around 1910 to 1940, the golden age of
the development of this industry that was nevertheless of artisanalnature. This also applied to a large share of patented inventions ongrowth media, which had little commercial value, except for mo-lasses treatment (Gelinas 2012). The risk of reverse engineering iscritical when determining patent or trade secret protection, espe-cially when technology is changing rapidly (Daizadeh and others2002; DuPre and Smith 2011). This appears to have been thecase with several of the early patented inventions on fermentationcontrol in baker’s yeast production.
Seed (Pure Yeast)Table 6 to 9 present patents related to seed yeast. This includes
processes for the preparation of pure yeast starters. Only a fewinventions were patented on the long-term management or keep-ing conditions of yeast starters (Table 6). Much more interest wasgiven to growth conditions, in particular, the acclimatization of
Figure 1–Number of patents and licenses filed by the Fleischmann/Standard Brands group on growth media (Gelinas 2012) and fermentation controlin baker’s yeast production.
Table 6–Patents published between 1900 and 2009 on seed preservation for the production of baker’s yeast.a
Inventor (publication year); priority date Country Patent nr. Details
Burmann (1917); September 15, 1916 CH CH 74939 A tube or small container contains sterile and solidified media (gelatinemixed with nutritive broth) and is seeded with pure yeast; for keepingand sending pure seed cultures
Hublot and Vallet (1961); August 9, 1960 FR FR 1272116 (BE605492)
To improve its long-term preservation (18 mo), yeast cultures are storedinto plastic packaging material allowing little gas exchange(polyethylene or polyvinyl chloride)
Cowan and others (1976); assigned toTruman Limited; August 3, 1973
GB GB 1425979 Mixed with mannitol (osmotic stabilizer), and β-phenyl ethanol(bactericide); storable seed yeast
aLinked to the inventor and publication year (left column), patent number refers to the earliest publication of the invention. Patents are listed according to filing date of the invention (priority). For Germanpatents, the priority date was based on the information disclosed in the publication (“Patentiert vom”), which was 1 d later than the “convention date” (filing date) cited in foreign patents. In case of multiplepublications and when available, the country of earliest filing is mentioned. For some entries, details of the main invention were published in several “basic patents” forming a “patent family.” When identicalversions of the same “basic patent” were issued in several countries, patent numbers are given in parentheses and without reference to the publication year. Identification of most of the country codes is given atthe bottom of Table 2.
seed yeast cells by growing it under adverse conditions likely to bemet during the large-scale yeast manufacturing process (Table 7).Some effort was also put to boost seed yeast activity so early effortsrecognized the importance of growing conditions that increasedprotein content in yeast gave higher gassing power (Table 7).
In the early days of large-scale baker’s yeast manufacturing, upto 1911, another concern was seed decontamination (Table 8). Afew patents also claimed the best ways to add starters to the maingrowth media (Table 9): as for sugar and nitrogen sources, thestepwise addition of yeast starters was finally recommended in 1943by Stich. Some interest was given on techniques to better estimatethe amount of seed yeast to be added in the fermentation vat.
Historical contextThe pure culture method took long to be adopted by the yeast
industry, so the quality of concentrated yeast available commer-cially remained quite variable until about 1930 (Frey 1930; Gelinas2010a). Up to around 1925, a very critical issue was seed harden-ing to inhibitory chemicals added to control infection during yeastmanufacturing. After that period, both the nature and concentra-tion of such chemical inhibitors probably changed because seedhardening to those toxic compounds was less an issue for inventors.Most of these rudimentary techniques were abandoned when con-trol of pure starter management and infection during large-scalefermentation was better understood by the yeast industry.
Around 1925 to 1935, much was already known on the bestpractice to manage seed yeast for baker’s yeast production. So, in1934, Kitzmeyer stressed the importance of rapid seed transfer onthe quality of final baker’s yeast (Table 7). This might be consideredas a breakthrough because, until then, little interest had been givento the activity of starters for baker’s yeast production, as shown byspecification of Kitzmeyer’s patent: « At one time in the yeastmanufacturing industry it was customary to initiate the growth ofyeast by placing a small portion of previously manufactured yeast ina suitable quantity of nutrient and increase in yeast in quantity bythe regular manufacturing process. Due to the fact that this oftencaused the yeast to become infected with wild yeasts and otherorganisms, this method has been generally abandoned. The presentpractice of handling yeast to be used to start the manufacturingprocess is similar to that employed in the routine handling of otherbacteriological cultures. The pure culture of yeast is obtained byknown methods, and is kept alive by transfer in liquid media suchas malt, other grain, or molasses solutions, or by growth on solidmedia preparations of agar or gelatine. The media are sterilizedand the technique of transfer is well known to bacteriologists. Ifsolid media are employed, they are kept in a tube or small vesselprotected from infection by a cotton plug. The yeast is introducedin very small quantity on a platinum wire, and the medium iskept at proper temperature until yeast growth is complete. Thenthe culture may be transferred to a fresh medium or may be kept
Table 7–Patents published between 1900 and 2009 on seed growth conditions for the production of baker’s yeast.
Inventor (publication year);priority date Country Patent nr. Details
Jacquemin (1903); June 23,1902
FR FR 322381 Acclimatized to inhibitory substances in nontreatedmolasses by growth with increased levels ofsulfuric acid; distillers’ yeast
Molhant (1914, 1921); May25, 1912 (FR)
BE FR 455483 (GB 191311617; AT66474); FR 471775 (GB191417009, not accepted)
Acclimatized to inhibitory substances by growth withincreased levels of hydrochloric acid, formol, orboracic acid
Verein derSpiritus-Fabrikanten inDeutschland (1919);Hayduck (1923); licensedto The Fleischmann Co. (USand CA); December 24,1915 (DE)
DE DE 303311 (FR 520523; US1449111; US 15716, Reissue; CA238181)
Acclimatized to acids by growth in acidic mediacontaining inorganic nutrients and sugar;alternative to sulfuric acid, to adapt seed yeastand protect it against infection
Stein and Reiser (1921);November 30, 1918 (AT)
CS AT 88648 (DE 337282; DK 27783) Acclimatized to inhibitory substances by mixing withsodium disulfide; infection tolerance, high gassingpower, and good keeping properties
Pollak (1923); April 4, 1922(AT)
CS; AT; US AT 102790; AT 105786 (DE480076; FR 564231; GB 195963;US 1677529)
Treated with enzymes to stimulate N-assimilationwhen yeast development slows down; yield
Hamburger and others(1925); MellemeuropaeiskPatent-Financierings-Selskab Aktieselskab(1925); March 3, 1924 (DE)
CS; DK FR 591896 (AT 109526, dependenton AT 83559; CA 258458; GB230050, not accepted)
DE GB 280861 (US 1774546) Grown only with organic nitrogen, then withincreasing quantities of inorganic nitrogen; to getseed with high-protein content and gassing power
Kirby and Frey (1933);assigned to StandardBrands Inc. (US only);licensed to TheInternational Yeast Co.Limited (GB only); January26, 1932 (US)
US US 2029572 (GB 390114) Grown under adverse conditions with large amountsof inorganic nitrogen (30% of total sugar); to gethigh-protein (over 50%) seed yeast; yield, color,gassing power, and keeping properties
Kitzmeyer (1939); November3, 1934a
US US 2150329 (CA 373608) Repeatedly transferred from solution to solution at aperiod between the time the sugar first showsreally appreciable depletion (every 3 or 4 d) andthe time when three-quarters of the growth timehas elapsed; to avoid seed degradation, andimprove yeast yield, color, gassing power, andkeeping properties
Effront and Popper (1936);Effront (1937); licensed toStandard Brands Inc. (USonly); November 23, 1934(FR)
FR; HU FR 794359 (US 2083598) Combination of seeds grown under differentconditions, where alcohol production is high orlow, depending on sugar concentration andaeration conditions; higher gassing power underalcohol-forming conditions
Levin (1947); January 17,1944 (Palestine)
GB; Palestine GB 588374 (US 2439572) Using a specific apparatus, liquid medium isgradually dropped on seed yeast (in cotton);gradual varying growth conditions (temperature,medium composition) harden seed yeast andeliminate contaminants
Shropshire (1949, 1951);assigned to RaytheonManufacturing Co.; October26, 1946
US US 2492128; US 2578491 Treated in a 360 cycles-vibrator and grown for about24 h; faster growth (about 50 times)
Grown under conditions hindering cells growth,allowing either low or high alcohol production,with nutrient starving and inhibitors (formalin;sulfurous acid), at low pH and temperature (12 to21 °C), and weak aeration; yield, color, andkeeping properties
Griesbach (1957); February 6,1956
US US 2802776 During growth, acid components are removed withan electrolytic cell; yield
Rost (1972); December 23,1970
DD DD 88927 As part of a continuous process, produced incontinuous (not in batch)
Cauchy (1972); assigned toNordon & Cie; March 11,1971
FR FR 2129018 As part of a continuous process, produced in a batchprocess allowing ethanol production and understrict aseptic conditions (filtered air)
Iwasaki and others (2006);assigned to KanegafuchiChemical Ind.; March 28,2006
JP JP 2006304780 Acclimatized in a synthetic and/or a low-sugarmedium; to limit the effects of varying mediacomposition
Grown in concentrated (specific gravity of 1.07) andhighly acidic media; to purify seed yeast (“bud”) aspart of yeast manufacturing
Henri and others (1910); November29, 1909
FR GB 190927798 Short treatment with ultra-violet rays to kill mostcontaminants in yeast starters for distilleries orbrewing; cheap alternative to pure cultures
Schimper (1912); partly assigned toA. H. Koeller; October 12, 1911
US US 1020716 Dead yeast, bacteria, small and light cells, and impuritiesare carried off under aeration and with wash water;mainly designed for pitching brewer’s yeast
aPublished before the year 1900 but not included in Gelinas (2010a).
Table 9–Patents published between 1900 and 2009 on seeding conditions for the production of baker’s yeast.
Inventor (publication year);priority date Country Patent nr. Details
Board and Board (1905); December7, 1904
GB GB 190426698 (DE180338)
Seed is added at 3 stages during the course of the mainfermentation; alternative to 1- or 2 steps for spirits, beer, vinegaror yeast manufacturing
Kamienski (1914); September 20,1912
DE DE 269192 Seed is added in 2 portions: two-thirds in diluted media and the restwith concentrated media; aerated; yield
Roth (1917); April 6, 1914 AT-HU (AT) AT 73173 Very high level of seed yeast (15% to 50%) is added to diluted(twice than normal) molasses-based media; yield and gassingpower
Stich (1952); February 14, 1943 DE DE 752269 (FR891981)
Seed is added at regular intervals to constantly provide highly activecells; gassing power
Burrows (1972); Burrows and Dear(1972); assigned to The DistillersCo. (Yeast) Ltd.; April 11, 1968
GB GB 1262639; GB1278784
To estimate dry matter and cells number in seed, specific gravity(mass of a given volume) or turbidity of a yeast suspensionpreviously separated to retain only large yeast particles isdetermined automatically with a specific turbidimeter; to allowrapid and precise determination of the amount of seed yeast toadd to fermentation tanks, and to determine final yeast yield
Donnelly and Cahill (2000); assignedto Guinness Limited; September14, 1999
IE EP 0987334 The amount and activity of seed yeast is measured by imageanalysis; cell volume decreases during storage, which is correlatedto viability (old cells tend to sediment); brewer’s yeast and baker’syeast
for some time in a cool place before transfer to another similartube, or to the vessel in which is started the first stage of the yeastmanufacturing process. As the yeast grows on the surface of thesolid medium, the increasing cells pile on top of each anotherand crowd along at the side of the colony so that the individualcells of the culture are subjected to a changing and wide varietyof conditions of moisture, nutrient concentration, alcohol, wasteproducts, air, and carbon dioxide. Most of the cells are subjectedduring most of their existence as units to an environment of smallamounts of nutrients and large amounts of yeast metabolic wasteproducts and are not in a state of active reproduction.»
Infection ControlCommercial baker’s yeast contains high levels of contaminat-
ing bacteria and wild yeast that impair its yield, gassing power,and keeping properties (White 1954; Reale and others 2013). Al-though lactic acid bacteria have generally been found in abundance(O’Brien and others 2008), wild yeasts (nonstarter types) appear tobe the most important contaminants of compressed baker’s yeast,consisting up to 10% of the viable biomass (Tracey and others1984; Viljoen and Lues 1993); for example, Candida krusei utilizesethanol excreted during the growth of baker’s yeast strains (Suihkoand Makinen 1981).
Most of the patented inventions for infection control duringyeast production were related to the addition of antimicrobials in
the growth media, including acids (Table 10). Antiseptics such asformalehyde, chlorine, or antibiotics were also proposed but hadsome inhibitory action against yeast itself, which explains whysome interest was put on seed-hardening to such toxic compounds(Table 7). Addition of such preservatives was important in the earlydays of baker’s yeast manufacturing (Gelinas 2010a) but, accordingto Table 10, this practice appeared to have been abandoned inthe early 1920s. However, since the 1950s, there have been afew patented inventions on the decontamination of both growthmedia and yeast itself. According to Table 10, patents were filed in1999 and 2006 on the addition of hop acids to control infectionduring the production of baker’s yeast, although the use of hopshas been patented as early as 1890 (Gelinas 2010a). To a lesserextent than for antimicrobials, some interest was given on thedesign of easy-to-clean equipment providing sterile conditions,including air.
Historical contextFor the baker’s yeast industry, infection control during fermen-
tation is a major subject because patenting activity showed a lastinginterest in these technologies. This is confirmed by the specifica-tion of a patent filed in 1926 by Distillers Co. Ltd. and Meyer(Table 10): « . . . it has been found impossible to prevent, at someperiod or other, the invasion of the fermenting liquid by un-desirable organisms. The gradual accumulation of these organisms
Table 10–Patents published between 1900 and 2009 on infection control during the manufacturing of baker’s yeast.
Inventor (publication year);priority datea Country Patent nr. Details
Verein der Spiritus-Fabrikanten inDeutschland (1901, 1902a, 1902b,1902c); February 16, 1900
DE DE 127355 (AT8977); DE 129577;DE 129302; DE127810
Cereal-based media acidified with butyric acid or lactic acid(instead of lactic acid bacteria starter)
Jacquemin (1901); February 7, 1901 FR FR 307950 Antiseptics (copper salts of acids; hydrofluorosilicic acid withformic acid) added to nonsterile distillery mash
Kusserow (1904); September 27, 1902 DE DE 152136 Hyposulfites; no discoloringLapp (1903); November 15, 1902 (DK)a DE DK 5719 Large storage tank (500 to 1000 hL) made from steel
instead of wood and with double walls to improve coolingand control infection
Somlo (1905); April 13, 1904 HU AT 19616 Oxalic acid; for distilleriesFritsche (1907); Jacquemin and Fritsche
(1906); November 9, 1904 (DE)AT-HU DE 179915; AT
27341 (GB190624093); FR361643
Formaldehyde in milk solution; reduced acidity; for distilleries
Forster and Finitzer (1910); April 10, 1909(DE)
AT-HU(HU)
US 978282 (GB191008652)
Acidified with sulfuric acid and fermented with lactic acidbacteria
Cohendy (1911); November 22, 1909 (FR) FR GB 191026773 (AT54818)
Apparatus for pure yeast production, with an inner and anouter vessel (with a single cover)
Pechstein (1912); assigned to GebruderJacob; February 3, 1910
DE US 1023032 Flexible easy-to-clean metallic hose pipe
d’Herelle (1912); October 22, 1910 (MX) FR FR 435373 Apparatus for pure yeast production; sterilizer andfermentation vat connected in closed circuit
Hess (1922); June 4, 1914 AT-HU(AT)
AT 88349 Molasses-based medium acidified with alum (aluminiumsulfate) instead of sulfuric acid, without harming yeast
Hayduck (1923); Verein derSpiritus-Fabrikanten in Deutschland(1919); licensed to The Fleischmann Co.(US and CA); May 8, 1915 (DE)
DE DE 303253 (US1449112; GB155288; CA238176)
Antiseptics (formaldehyde; formic acid) added to dilutedgrowth media
Donham (1917); assigned to SprayEngineering Co.; December 6, 1915
US US 1222541 Air purifying device installed between the air compressorand the fermentation tank
Magne (1917); June 19, 1916 FR; MX US 1212656 (GB124237)
Apparatus for the production of pure yeast, including airsterilizing mechanism
Etablissements Poulenc Freres, and Vigreux(1924); Vigreux (1927); March 17, 1923(FR)
FR FR 575518 (US1623896)
Large-scale apparatus for pure yeast production withautomatic controls (media sterilization, temperature, andso on)
Pollak (1927); September 29, 1923 CS; AT CS 23232 Lactic acid bacteriaKlein (1926); December 30, 1924 (US) US AT 103908 Lactic acid (high levels)Meyer (1933); The Distillers Co. Limited and
Meyer (1927; 1930); licensed to StandardBrands Inc. (US only); May 4, 1926 andMay 1, 1929 (GB)
Growth at 13 to 15 °C for 16 to 19 h, then at 25 to 30 °C for 4 to 7h, under aeration and with high level (8%) of seed yeast in abudding state; yield (oxygen transfer is higher at lowtemperature)
Kierulff (1911); October 5, 1910a DK DK 15072 Yeast is activated at 24 °C, then growth is performed at 15 °C withaeration for 4 h in dilute medium, and fermentation ends at 28 to30 °C for 4 to 6 h; yield
Wahl (1921); July 26, 1919a US US 1373468 Yeast propagator is equipped with cooling system (inner wall) tocool rapidly growth media (20 to 25 °C); infection control
Lavedan (1929); July 1, 1925 US US 1718910 Injection of carbon dioxide during yeast growth to control acidityand temperature; yield and keeping properties
Buhrig (1931); assigned to StandardBrands Inc.; January 22, 1926
US US 1817232 The outer surface of the tank is subdivided into several independentzones containing cooling liquid
Horch (1931); February 20, June 4,October 4, and October 14, 1930(DE)
DE FR 705807 (DE543775; DE587638; CH151946; US1937226; AT127776; AT134864)
Cool air is circulated in a jacket in contact with the liquid in thefermentation vat; improved temperature control compared tocooling units placed inside or rolled around the vats
Strauch & Schmidt (1932); January15, 1931
DE DE 543549 Heat insulating cooling jacket is provided for yeast storagecontainer; more efficient than refrigeration chambers
Knappe (1937); licensed to LarsBrandstrup (DK); March 10, 1933(DE)
DE DE 641753; DK51473
Low-temperature (16 °C) growth in media with plant proteinhydrolyzed with phosphoric acid
Meyer and Chaffe (1942); TheInternational Yeast Co. Limitedand others (1940); licensed toStandard Brands Inc. (US only);December 22, 1938
GB GB 523019 (US2304471)
Growth at a lower temperature than optimum (30 ºC for 4 h, 24 ºCfor 6 h and, facultative, 30 ºC for 2 h); yield
Griesbach (1955); May 8, 1951 US US 2705215 Controlled heating (43 to 63 °C) of small portions of growth mediawhile the main culture is at a normal temperature (21 to 32 °C);yield and infection control
Suzuki and others(1989); assigned toKirin Beer Kabushiki Kaisha;January 8, 1988
JP EP 0325907 (US4906578)
Internal cooling jacket secured concentrically to the inner wallsurface and with close contact with the fermentation tank; highheat transmission and easy-to-wash; probably for small-scale only
aBreakthrough.
always produces a degeneration in the quality of the yeast obtained,so that it is necessary to stop the process and restart the operation.It is of course the usual procedure in discontinuous methods ofyeast manufacture to add sufficient quantity of either a mineralacid to inhibit the growth of foreign organisms, but it has beenfound that when this acidity has to be maintained throughout along period the yeast after a time becomes sluggish in growth and,moreover, tends to deteriorate in quality. »
According to a patent by Valentin Lapp cited in Table 10, inthe early years of yeast manufacturing, yeast storage tanks weremade of wood. These vats were difficult to clean and refrigerate,which suggests that this was a major source of infection of seedyeast and any yeast stored in the liquid state. Filed in 1902, thispatent that recommended the use of steel tanks so this inventorappears to have been the first to propose a long-term solution toyeast infection.
Even nowadays, fermentation conditions associated with thegrowth of baker’s yeast are not performed under absolutely sterileconditions. To reduce bacteria and wild yeast contamination to aminimum, growth medium is now sterilized, air is filtered, andequipment is thoroughly cleaned. The number of patented in-ventions (30 between 1900 and 2009) on the control of infectionduring baker’s yeast manufacturing is probably not very indicativeof the economical importance of this matter. Thanks to numer-ous nonpatented technologies such as easier-to-clean equipmentsand the strict application of hygienic procedures, much of theseproblems were solved. This improved yeast yields, gassing power,
and keeping properties due to the elimination of excessive levelsof wild yeast and bacterial contaminants.
Temperature ControlMuch heat is produced during yeast growth. This has encour-
aged the filing of a few patent applications on the temperature con-trol of fermentation media for baker’s yeast (Table 11). Inventorswere mainly interested in designing cooling systems for fermenta-tion and storage vats (6 patents) or to specify temperature that weresaid to improve yeast properties (5 patents). Specifically for thebaker’s yeast industry, the interest for temperature control droppedin the early 1950s. However, it is likely that much more patentedinventions were later issued on miscellaneous fermentation vats.
Historical contextNowadays, baker’s yeast is generally grown at 27 to 30 °C.
Around 1900, it was already known that 28 to 38 °C was themost favorable for yeast cell multiplication. According to a patentspecification filed in 1908 by Braasch (Table 11), it was customaryto begin the fermentation at about 22 to 23 °C so most of thefermentation would occur at 25 to 30 °C due to the heat formedduring cell growth. However, according to a patent specificationfiled in 1926 by Buhrig, cooling systems were not very efficientbecause they were based on the temperature of water. For exam-ple, seasonal variations were seen and this might partly explainwhy yeast propagation was mainly practiced in Nordic countries.According to this author, it was a common practice to conduct
Table 12–Patents published between 1900 and 2009 on the concentration and rate of addition of sugar-based ingredients during the manufacturingof baker’s yeast.
Inventor (publication year);priority datea Country Patent nr. Principleb Details
Vignier (1905); February 9, 1904 FR GB 190403196 R Wort is supplied at regularly occurring periods;distillers’ yeast combined with wine or beerproduction
Verein der Spiritus-Fabrikanten in Deutschland(1919); Hayduck (1923); licensed to TheFleischmann Co. (US and CA); March 17, 1915a
DE DE 300662 (US1449105,invalid; GB155284; CA238172)
R In highly diluted media (1°B), a wort of higher sugarconcentration (12 °B) is added at a minimal rate,with aeration, to allow minimal alcohol formation;yield
Schwarz (1921); with depending patents by Klein(1923; liquid media), MellemeuropaeiskPatent-Financieringsselskag (1927; seed growth),and Jacobsen (1929; continuous culture); April 8,1915
AT AT 83559 (AT103075; AT109526; AT130435)
R; Q Nutrient medium is added progressively, based onanalyses (sugar, acidity, nitrogen, phosphoric acid,alcohol, and yeast), with little sugar excess; yieldand gassing power
Kraus Moskovits EgyesultIpartelepekReszvenytarsasag (1923); November 24, 1915(HU)
HU HU 70215 (GB174628)
R In diluted media, concentrated and acid-controlledmedia is added gradually, avoiding alcoholformation; yield
Dupire (1920); April 23, 1919 FR FR 498590 (GB149438)
C Growth medium is diluted with water (final density is1030 g/L) in such a proportion that yeast findsonly the quantity of sugar that is necessary for itsfull development
Aktieselskabet Dansk Gaerings-Industri (1920); Sak(1924); licensed to Vereinigte Mautner’schePresshefe-Fabriken Gesellschaft m.b.H., andEugene Fould-Springer (AT only); licensed to TheFleischmann Co. (US and CA only); July 5, 1919(DK)
R To compensate for nutrients assimilation duringgrowth, highly concentrated growth medium isadded to a less concentrated medium at suchspecific rate that much alcohol (20%) is formedand later assimilated during the latter part of thepropagation; to allow joint manufacturing ofalcohol and yeast; yield
Sak (1919); Aktieselskabet Dansk Gaerings-Industri(1919); licensed to Vereinigte Mautner’schePresshefe-Fabriken Gesellschaft m.b.H., andEugene Fould-Springer (AT only); licensed to TheFleischmann Co. (CA only); July 5, 1919 (DK) andJuly 15, 1919 (NO)a
DK NO 39412 (SE56428; FI 9712;FR 503808; CH94210; NL8737;GB146947, notaccepted; AT105784; CA209947; CA237961); FR503810 (CA209948; CA237962)
R To compensate for nutrients assimilation duringyeast growth, specific amounts of growth mediaconstituents (one or several) are addedincrementally, according to specific curves;without joint alcohol manufacturing; yield
Allen and Timmer (1930); Vitamin Food Co., Inc.(1931); December 14, 1925
US US 1775800 (GB361026)
R Use of highly diluted media and excess aeration toprevent media acidification; yield
Bratton (1930); assigned to Anheuser-Busch, Inc.;March 6, 1926a
US US 1767646 C; R Nitrogen-rich yeast is first obtained by feeding withsugar-deficient medium (rich in protein andnutrient salts) and, later, it is slowly fed withsugar-rich medium (deficient in protein andnutrient salts)
Knappe (1933); March 21, 1926 DE DE 570932 R Yeast is fed stepwise with just enough growthmedium to double cell concentration, until it ismature (burgeoning is completed), and newmedium is added in concentration sufficient todouble again the yeast cell concentration; yieldand gassing power
M. Fisch’s Sohne and Rosenberg (1930); Braun andothers (1931); December 18, 1928 (AT)a
AT; CS AT 119946 (DK47188; FR686784; GB346361)
R Divided into several phases of short duration,feeding rates increase according to calculatedmaximum cell growth (logarithmic) and fullconsumption of sugars, using a series of containers
HU FR 692546 (DK44716; DE568756; AT125192; GB349201; CH154496; US1962831)
R; C Near the end of fermentation, yeast is grown innitrogen-rich media (sugar-limited), acidified, thenswitched to glucose-rich media (nitrogen-limited);yield and gassing power
Jellinek (1931); assigned to VereinigteMautner-Markhof’sche Presshefe Fabriken undAktien-Gesellschaft Ignaz Kuffner & Jacob Kuffnerfur Bauerei, Spiritus- und PresshefefabrikationOttakring-Dobling (AT only); licensed toHefefabriken A.-G. (CH only); licensed to ArthurKoenig (DK only); October 22, 1929 (AT)
AT AT 130438 (GB354118; FR704113; US1920395; BE374358; BE374996; CH153184; DK46078)
R; C Highly active yeast (protein-rich) is fed with highlyconcentrated sugar-based medium to allow muchethanol production; after separation, yeast isslowly fed for 6 to 8 h with the previous mediumcontaining ethanol; yield and keeping properties(lower protein content)
Inventor (publication year);priority datea Country Patent nr. Principleb Details
Wroten (1933); March 19, 1930 US US 1917283 R; Q Weight of added sugar is constantly lower than theweight of yeast, using a large proportion ofinorganic nitrogen salts and without acidneutralization; when sugar has been assimilated,this process is repeated; to obviate the necessity ofconstant supervision, the acidity or gravityreadings are determined throughout the run andthe handling of large volumes of liquid
Stich (1934); licensed to Standard Brands Inc. (CAonly); March 3, 1933 (GB)
DE GB 411611 (CA371677)
R At hourly intervals, the amounts of air and molassesincrease according to exponential yeast growthcurve; yield
Lutz and Irvin (1937); assigned to National GrainYeast Corp.; July 1, 1933a
US US 2084736 C; R Yeast is seeded in a small quantity of growthmedium and fed with a larger volume of medium(2 to 10 times that of the initial wort compared to0.25 times, normally); less media and improvedaeration; yield and cost
Norddeutsche Hefeindustrie Aktiengesellschaft(1935); September 26, 1933
DE GB 431129 (notaccepted)
C; R Seed yeast is mixed with sugar-free media containingphosphoric acid (avoiding alcohol formation), andfed incrementally with sugar-containing media
Kitzmeyer (1937); October 14, 1933a US US 2097292 (CA352872)
R Yeast is fed with a sugar solution at an increasingrate and using a specific time schedule (19 steps),providing brief periods where no sugar is available(to limit pH fluctuations); alternative tocontinuous sugar feed; no hard lumps incompressed yeast; for high-sugar dough; gassingpower and keeping properties
Hilbers (1938); January 7, 1936 DE AT 154818 (US2162217)
R; Q Acid is controlled by stopping feeding andcontinuing aeration; yield and keeping properties
Irvin and Mead (1939); July 28, 1937 US US 2183570 C; R Yeast is first grown under batch conditions (7% to10% seed instead of 15% to 25%, much sugar,and low aeration; 6 h); after water addition,aeration is increased and growth medium is addedfor 8 h; less seed and air; yield and cost
de Becze (1939); January 26, 1938 (DE) US FR 849426 (US2199722; GB524312)
C; R Yeast is grown in very dilute media (80% to 90% ofthe final volume) and fed stepwise by appropriateadjustment of seed yeast, aeration, and nutrients(15% to 25% sugar); yield and gassing power
Berkel (1952); licensed to AktiengesellschaftJungbunzlauer Spiritus- und Chemische Fabrik(1949; AT only); February 5, 1943 (DE)
DE DE 767347 (AT164248)
C Yeast is fed with easy-to-ferment media and,progressively, with difficult-to-ferment media(concentrated molasses by-products); cost
Aktieselskabet Dansk Gaerings-Industri (1949);February 20, 1946 (DK)
DK DK 68667 (FR941938; CH276131)
C Growth in concentrated media and reduced aeration,followed by dilution and fermentation undernormal aeration; reduced air consumption; cost
Aktieselskabet Dansk Gaerings-Industri (1968);August 28, 1954
DK DK 108781 R Constant addition of concentrated medium withoutalcohol production, using a specific yeast strain;higher gassing power in lean dough
Pyke and others (1958); assigned to The DistillersCo. Limited; November 17, 1954
GB GB 800030 (FR1137889)
R An excess of molasses is added exponentially for 2 to3 consecutive stages followed by optimizedfeeding; to increase maltase activity (non-sugareddough); gassing power
Patentauswertung Vogelbusch Gesellschaft m.b.H.(1960); Rungaldier and Braun (1961); MautnerMarkhof (1961); all assigned to PatentauswertungVogelbusch Gesellschaft m.b.H.; November 14,1958 and December 14, 1959a
AT AT 208802 (CH379444; DK91861; DE1080048; FR1236196; GB882476; US3002894); AT214392 (DK96261; CH394090; DE1152984; GB897166; US3010881)
Q A portion of alcohol in outlet of aeration system iscontinuously measured (by colorimetry orcalorimetry) and signal is transformed into electriccurrent, which controls nutrients and aeration;yield
Svenska Jastfabriks Aktiebolaget (1964; 1965);February 5, 1963 (SE)a
SE FR 1379225 (GB1035552); FR1390262 (GB1035551)
Q Using an apparatus for analyzing alcohol anddissolved oxygen (electrode), feedback control ofthe oxygen transfer is performed by varying therate of rotation of the agitator and/or the surfacetension of the medium with antifoam
Ceskoslovenska Akademie Ved (1965); Caslavskyand Hospodka (1968); October 11, 1963 (CS)
CS FR 1418296 (GB1045930; US3384553)
Q Dissolved oxygen content is determined with apolarographic electrode equipped with anoxygen-permeable membrane and connected witha regulating device for metering nutrient feed
Oriental Yeast Co., Ltd. (1971); March 29, 1967 JP GB 1220101 R Based on a 2-stage process, sugar feed rate isswitched from high to low, providing alternatingfeed and non-feed periods; sweet dough (15% to25% sugar); gassing power and keepingproperties
Murayama and Takemoto (1985); assigned to ToyoSoda Kogyo KK; December 28, 1983
JP JP 60141283 Q Respiratory quotient (molar ratio the carbon dioxideformed to the oxygen consumed) is determinedonline and controls feed rate
Knackmuss and Asperger (1986); assigned toAkademie der Wissenschaften der DDR; August 9,1984
DD DD 231803 R Glucose concentration is set (0.1 to 0.3 g/L) andcontrols molasses feed or air incorporation;gassing power
Albrecht and others (1985); Chalupka and others(1986); assigned to Akademie der Wissenschaftender DDR; May 24 and June 21, 1985
DD DD 225437; DD238627
Q; R Feeding rate for molasses is controlled by theethanol concentration in the fermentor,programmed to increase according to yeastconcentration; to reduce molasses consumptionand to slowly progress from an anaerobic stage toan aerobic stage; cost
Kell and Todd (1988); September 22, 1986 GB WO 8802115 (US4810650)
Q Yeast concentration is determined by an apparatusmeasuring differences of capacitance; to controlfermentation parameters
Nakamura and others (1992); assigned to AjinomotoCo., Inc.; November 30, 1990 (JP)
JP FR 2669935 (US5912113)
Q Sugar feeding rate is controlled by carbonconcentration, obtained by monitoring pH ordissolved oxygen; preferable to ethanoldetermination; yield
Tuljakova and others (1994); assigned toAssotsiatsijaproizvoditelejoborudovanijaikhle-bopekarnykhdrozhzhej; January 28,1992
RU RU 2016896 C Specific nitrogen–carbon ratio (1:8) for 2generations
Ono and Tashimo (1994); assigned to KanegafuchiChem. Ind.; October 7, 1992
JP JP 61113822 R Feed rate is reduced in the 2nd half of thefermentation; yield
Bishop and others (1997); assigned to G.D. Searle &Co.; August 12, 1994
US US 5595905 Q In real time, a computer calculates nutrientsconsumption and feed rates by comparing thenutrients concentrations of samples
Ishii and others (1997); assigned to Oriental YeastCo., Ltd.; August 31, 1995
JP JP 9065873 Q Model is based on integrated value of the differencebetween sugar flow acceleration value andtheoretical sugar flow not producing ethanol; yield
Mead and Van Urk (1997); assigned to DeltaBiotechnology Limited; March 13, 1996
GB WO 9733973 (US6150133)
Q Electrical conductance of the fermentation mediumis determined at intervals; algorithm compareschanges with predetermined value; acetic acid(toxic) is determined
Plomp (1998); assigned to Gist-brocades; July 26,1997a
NL EP 0821057 (US5916609)
C; R Slow fed-batch growth (more than 20 h) in anon-molasses carbon source, without washing andconcentrating, and to get a yeast concentrate(10% to 22% solids); to reduce waste water andgive cheaper yeast with improved taste and aroma
Lendl and Schuster (2002); assigned toInnovationsagentur Gesellschaft m.b.H.; April 5,2001a
AT WO 02082061(US20040096930)
Q Rapid (5 min intervals) and on-line measurements onmedia and microorganisms which are directlyspectroscoped (infrared) to determine yeast cellscomposition (glycogen, trehalose, mannan,protein structure, and so on)
Wagner (2003); May 16, 2002 DE DE 20207697U Q Alcohol is continuously measured; to control nutrientfeed
Korneev (2004); December 15, 2002 RU RU 2230111 Q Portions of yeast biomass are removed, based oncells growth stage
Kimura and others(2006); assigned to AsahiBreweries Ltd; April 4, 2005
JP JP 2006288201 Q Respiratory quotient (inflow and exhaust gas) ismeasured by mass spectrometry, to controlfeeding
aBreakthrough.bC, concentration (sugar); Q, quality control; R, rate of addition.
yeast propagation in large tanks often formed of copper over theouter surface of which a cooling liquid, usually water, was allowedto flow at suitable temperature for preventing undue rise of thetemperature of the material within the tank during yeast growth.In such prior processes in which the cooling liquid was allowed toflow over a unitary zone comprising substantially the entire heightof a usual fermenting tank, the cooling was not effected in themost efficient manner, one reason for this being that unless thecooling liquid was supplied in unduly large and wasteful quanti-ties its temperature approximated that of the contents of the tankadjacent its inner surface after the cooling liquid has descendedover a fraction only of the total height of the surface over which itflowed. After this approximate equalization of temperature, it nolonger exerted any cooling effect while passing over the remainingsurface of the tank.
According to a patent filed in 1938 by Meyer and Chaffe, «It is known to carry out a fermentation for the production ofyeast by operating for the entire fermentation period at the op-timum temperature known for any given organism and it is alsoknown to work at that temperature until shortly before the endof the entire working period and then to raise the temperaturesomewhat to improve the quality. It is also known to initiate fer-mentation at a temperature below the optimum temperature andthereafter raise the temperature during the course of the fermen-tation.» In several of the patents cited in Table 11, the use oftemperatures much lower than standard (27 to 30 °C), even as lowas 13 to 15 °C, was recommended to improve yeast yields. How-ever, such low growth temperatures were proposed until the 1930swhen yeast yields and cooling requirements were lower than in thefollowing years. Using such low temperature was also beneficialto yeast growth because of improved oxygen transfer. In somepatents, low fermentation temperatures were also said to controlinfection. However, in modern yeast production, it might not beeconomically feasible to use temperatures lower than 27 to 30 °Cbecause yeast yields would be too low.
Sugar Concentration and Rate of AdditionThe following section presents patented inventions on the con-
trol of sugar in yeast fermentation media, which is one of the mostimportant issues in baker’s yeast production. Table 12 applies tothe development of fed-batch conditions in which basic growthmedium is regularly supplemented with nitrogen-rich molassessolution. Table 13 describes inventions where portions of growthmedia were regularly removed during the course of the fermen-tation, to control the sugar concentration in fermentation media.Generally called the addition-withdrawing method, the latter issomewhat related to the concept of continuous culture. Althoughnot considered in this review and in the list of patents counted (Ta-ble 1), Table 14 presents a short list of patents on ethanol recoveryas part of baker’s yeast production. Mainly filed around 1910, suchpatented inventions suggest that early control of sugar feeding wasnot very thorough and allowed substantial alcohol formation atthe expense of yeast yield.
Historical contextAcceptable baker’s yeast was available around 1905 to 1915
in some European countries (Gelinas 2012). Control of sugarconcentration in fermentation media was applied as part ofthe “aeration process” giving high biomass yields because largequantities of air were blown in fermentation tanks. This processwas introduced around 1890 and by-passed the so-called Viennaprocess where no aeration was provided and yeast was allowed to
freely float to the surface due to natural gas production during itsgrowth (Gelinas 2010a).
During that period, the idea of adding nutrients gradually to themain fermentation medium was not new because this had beenpatent-protected in 1879 by Rainer (Gelinas 2010a). According tothe latter literature review, applications of this idea were later de-veloped by Levy, Jacquemin, and, in 1904, by Vignier (Table 12)who added fractions of growth medium to stimulate alcoholicyeast growth. Although granted only in 1919 due to World WarI, an important series of 13 German patents were filed within 18mo from February 1915 to August 1916 by Friedrich Hayduckwho assigned the inventions to Verein der Spiritus-Fabrikantenin Deutschland. This series of patents addressed most aspects ofmodern baker’s yeast production, including the control of sugarconcentration in growth media. In essence, baker’s yeast was fedat a minimal rate to avoid alcohol production, by adding concen-trated sugar-based media to diluted media in the vat. Such an ideawas very close in nature with the concept proposed by JacquesRainer in 1879. However, this inventor added dilute media tothe fermentation vat which required vats of increased volumes, sothis was a major problem for the large-scale production of baker’syeast.
Shortly after Hayduck filed his 1st patent specification onthe controlled addition of nutrients in baker’s yeast produc-tion (February 24, 1915), other patents with closely relatedspecifications were also filed: on April 8, 1915, in Austria bySchwarz and on November 24, 1915, in Hungary by KrausMoskovits. On April 23, 1919, Dupire also adapted this con-cept and filed a closely related patent specification in France. In1919, Søren Sak (1883 to 1950), technical director at Aktieselska-bet Dansk Gaerings-Industri (Copenhagen, Denmark), improvedthe original idea by increasing substrate concentration or rate ofaddition, to compensate for yeast growth. In 1928, Braun and oth-ers recommended short feeding curves for optimal yeast growth,to get about 3% to 5% yeast cells (dry matter basis) at the end of thefermentation. However, these patented inventions were backed bylittle scientific knowledge on baker’s yeast physiology. It was notuntil 1929, or several years after the baker’s yeast industry hadapplied these concepts, when it was scientifically recognized thatyeast growth was inhibited by large amounts of sugar, a conceptcalled the Crabtree Effect (Barnett and Entian 2005).
According to Table 1, 12, and 13, the interest for inventionson the control of sugar concentration peaked around 1915 to1935, although the number of patents was low with about 1 peryear. At the end of the 1950s, much more interest was put onquality control tools when devices for measuring ethanol weredeveloped to confirm that sugar concentration in the growthmedium did not inhibit cell growth, so high yields of yeast couldbe obtained. Interest for such technologies lasted until the recentyears. In the scientific literature, much effort was put on the opti-mization of feeding control for sugar and other nutrients throughmathematical models. Respiratory quotients were determined aspart of various fed-batch fermentation processes, including baker’syeast and antibiotics manufacturing (Johnson 1987; Reyman 1992;Beuermann and others 2012). In addition to the control of sugar,aeration was a very important limiting factor leading to reducedbiomass yields through the production of excessive amounts ofethanol, which may have negative impact on the yeast resistanceto stresses during bread manufacturing, including frozen dough(Gelinas and others 1989; Viera and others 2013). As recalled byRolf and Lim (1985), a small amount of ethanol production dur-ing yeast growth is beneficial for acceptable baker’s yeast showing
Table 14–Patents published between 1900 and 2009 on alcohol recovery during the manufacturing of baker’s yeast.a
Inventor (publication year)priority date Country Patent nr. Details
Maschinenbau-AktiengesellschaftGolzern-Grimma, and Zeckendorf (1911);November 5, 1910 (DE)
DE; US DE 240473 (AT55758; GB191122411; FR434949)
At the outlet of the aeration system, alcohol is recovered bymixing air with steam and condensed
Maschinenbau-AktiengesellschaftGolzern-Grimma (1913); November 8,1911 (DE)
DE DE 255300 At the outlet of the aeration system, alcohol is recoveredwith solvent-impregnated fabrics which is regularlysqueezed
Fischl and Schick (1913); February 5, 1912 HU AT 57434 Vessel is covered with wire netting to condense alcoholPfalzische Presshefen- und Spritfabrik
(1924); March 9, 1923DE DE 399894 Vessel is covered with a pipe system with showers
aNot included in the list of patents on baker’s yeast production (Table 1).
high gassing power. This was confirmed by Zamani and others(2008) who showed that slightly higher sugar concentration in thegrowth medium had a slight depressing effect on yield, althoughit improved nitrogen assimilation, which resulted in higher doughleavening ability and improved shelf-life.
Continuous withdrawal-addition process. A more sophisticatedway to control sugar concentration in the growth medium wasthe “continuous withdrawal-addition process” that consisted inpumping out growth medium at a specific rate to recover yeastand replace spent growth medium. Again, such a process had beenpatent-protected in 1879 by Rainer who proposed “the successiveadditions of peptones and hydro-carbons to the propagating liquidtogether with the successive removals of the yeast produced.” Inthe 1920s, as shown in Table 13, this became a very popular con-cept that was likely to eliminate frequent stop of yeast productionto recover biomass and clean fermentation tanks.
In the early years, inventors simply recommended withdrawal ofportions of growth media so yeast could be harvested continuously.To a lesser extent, some inventors also saw some opportunities forrecycling spent growth media. From 1925 to the 1980s, most of thepatented inventions on this process described very specific equip-ment for controlling fermentation, including feed and withdrawalrates of the growth medium. According to patent activity, interestin technologies related to continuous culture lasted longer thanfor the improvement of fed-batch processes. According to a patentby Knappe (1933) cited in Table 11, infection problems with so-called addition-withdrawal continuous processes were more im-portant than true economical benefits, so this process did not findwidespread application. Hence, about 1 century after the imple-mentation of modern production practices, baker’s yeast is stillproduced with a discontinuous or fed-batch process.
Nitrogen Concentration and Rate of AdditionTable 15 presents a list of patented inventions on nitrogen con-
trol during baker’s yeast manufacturing. In the early days of thistechnology, this aspect was a critical issue, although not as much asthe control of sugar concentration in growth media. Most of thepatented inventions in 1900 to about 1950 proposed the best com-binations of organic and inorganic nitrogen sources, with thoroughcontrol of acidification. Several attempts were made to use inor-ganic nitrogen salts instead of miscellaneous nitrogen-rich plantextracts. To control pH, inventors also recognized that slightlyacidic conditions were essential for controlling yeast infection, butthe addition of inorganic nitrogen-based compounds caused pHfluctuations, which had a negative effect on yeast growth and over-all quality. This is why some authors proposed to indirectly controlpH with specific nitrogen-based ingredients.
Historical contextIn the early days of baker’s yeast production, cereal-based me-
dia were the main growth medium and little interest was givento alternative sources of inorganic nitrogen sources. Malt sproutswere generally used in addition to malt as a source of nitrogenousfood. Besides ammonia, interest in organic sources of nitrogen forgrowing yeast lasted until the 1930s (Gelinas 2012). During thatperiod, it was already known that yeast could be nourished withorganic or inorganic nitrogen, the latter being much cheaper thanmalt sprouts. In growth media, yeast cells first take up the ammo-nium salts, as ammonia, because of its simple composition, insteadof organically combined nitrogen. However, it was not possible togrow yeast solely with inorganic salts of ammonia because yeastyield and gassing power dropped markedly.
According to Hamburger and others in a German patent filedin 1924, when mineral salts are used as the sole or main sourceof nitrogen in growing yeast, the acidity of the fermenting massincreased at the rate at which the ammonia was consumed by theyeast. For this reason, the mineral acids liberated by the action ofthe growing yeast were usually rendered innocuous by neutraliza-tion. This measure did not remove the anions of the mineral acids,which adversely affect the growth and the quality of the yeast. Ithas therefore been the practice to employ free ammonia which wasconsiderably more expensive than, for instance, ammonium sulfateand moreover necessitates a most careful control of the fermenta-tion process. For example, ammonium salts are added to substitutefor organic nitrogen sources because they are cheaper and stimu-late yeast reproduction. Yeast manufacturers preferred the organicsource of nitrogen because it produced yeast with greater gassingpower and keeping properties. On the contrary, yeast preparedwith inorganic nitrogen has the disadvantage that, while it is veryrich in protein, it is not durable and its fermenting power, whichis very good at first, decreases in a very short time. As cited inGelinas (2012), to obtain the best color of the finished product,it is necessary to closely regulate the degree of acidity producedduring the period of yeast propagation (King 1935).
Compared to sugar concentration, few quality control toolsappeared to have been patent-protected for the surveillance of therate of addition of nitrogen in yeast growth media. It seems thatpH determination was the main quality control tool. In 1953,Olsen proposed to determine excess nitrogen in growth media,using the well-known “formol degree” test which was adopted bythe yeast industry.
ConditioningWhen the feeding period is over, yeast may be ripened or treated
to improve its properties, as shown by 15 patents described inTable 16. Most of these efforts have been made to stimulate yeastgassing power and keeping properties, for example, with intense
aeration for several hours. A few patents described treatments forreducing off-flavors in baker’s yeast, in the fermentation vat andprior to harvesting.
Historical contextIn the early days of baker’s yeast technology, contamination
(infection) of baker’s yeast was of major concern as this reducedits gassing power and keeping properties (Gelinas 2010a). Whenfeeding was completed, a ripening period was proposed by Braaschin 1909, allowing continued aeration. This step appeared to havebeen readily adopted because it was mentioned in most of thepatents issued later. In some cases, prior to harvesting, yeast wasfed with specific nutritive solutions to suppress cell budding andimprove its keeping properties.
Major BreakthroughsImportant breakthroughs have been obtained from patents on
the control of fermentation during the production of baker’s yeast.
A. Fed-batch process: Gradual addition of nutrients is the heart ofbaker’s yeast production. Such an inventive idea was developedin 1879 by Rainer (Gelinas 2010a) so, contrary to commonknowledge, patents filed between 1915 and 1935 were adapta-tions of this concept. Addition of concentrated growth mediato a diluted solution (and not the contrary) was the most use-ful improvement by Hayduck in 1915. Rates of addition wereprecised by Sak in 1919. Compared to the batch process whereall ingredients are added simultaneously, the fed-batch processgreatly improved yeast yield, gassing power, and keeping prop-erties.
B. Infection control: As reported in Gelinas (2010a), pure seedyeast and sterile growth conditions were already applied inthe 19th century for the production of miscellaneous foods,including baker’s yeast, beer, and so on. In the early daysof bakers’ yeast manufacturing, hygienic conditions of large-scale fermentation vats needed much improvement. One goodexample was the abandonment of wood fermentation tanks,an innovative idea proposed by Lapp in 1902. Much later, in1934, Kitzmeyer stressed the importance of repeated transferof yeast starters from growth media, to avoid its degradation.
C. Temperature: The importance of temperature control has longbeen dismissed in large-scale fermentation. However, effectivecooling units did not appear to have been proposed for suchapplications until Wahl filed his patent specification in 1919.
D. Acidity control, nitrogen feeding: The optimal combinationsof nitrogen sources (organic or inorganic) were difficult todetermine. Thanks to a series of patent applications filed byHayduck in 1915, the importance of gradual feeding of ni-trogen sources was made popular in the industry. However,the main contribution of these patents may be the use of in-organic nitrogen. This has led to the development of severalpatented solutions for finding the right combinations of nitro-gen sources, to avoid overacidification of the growth medium.
E. Ripening: The importance of the final steps of yeast growthwas recognized very early as shown by the patent specificationsby Braasch in 1909, allowing a short period of starving to allowcells to complete their growth cycle and form some reservematerial. This simple idea had a major impact on yeast keepingproperties and was widely adopted by the yeast industry.
F. Quality control: Thorough control of the fed-batch processwas not available until the 1950s when Olsen, in 1953, andVogelbusch, in 1958, respectively, proposed to measure ni-trogen in the growth medium and ethanol in the outlet of
aeration units. This has led to a series of patents describingimproved units for the optimization of feeding curves.
Technological Lessons from Patents on FermentationControl
This review of the patent literature on fermentation control forbaker’s yeast production shows that, contrary to common belief,many of the innovative ideas in this sector were developed in the19th century, not in the 20th century. Nowadays, several of thepatented inventions developed after 1900 may be regarded as im-provements on former innovative ideas. This may explain whyessential patents for the yeast industry, such as those developed byHayduck in 1915, were later invalidated in courts. This strange sit-uation indicates that it may be very difficult to claim inventorshipon processes. It is likely that many inventors and companies de-cided not to patent their innovative ideas, preferring trade secrecyto keep technological advantages without disclosing their claimsto competitors.
Fermentation control of baker’s yeast production has been atthe forefront of the development of several industrial fermentationtechnologies. Since the 1950s, thorough quality control tools wereproposed and this certainly helped much to assure the productionof baker’s yeast with constant quality.
Impact on the Baking IndustryIn 1900, the cost of baker’s yeast was a serious obstacle to its
widespread use by bakers. Reduction of yeast quantities in doughwas a major concern for bakers, and this led to the development ofseveral additives for stimulating yeast activity or improving doughgas retention, including potassium bromate. Getting yeast withhigh gassing power and good durability was also a concern. Yeastwith a pale color was important; crumbling qualities and absenceof off-flavor were also mentioned in several patent specificationson yeast fermentation control.
Along with the optimization of growth media (Gelinas 2012),improvement of fermentation control during baker’s yeast produc-tion greatly reduced its cost due to increased yields and reducedcontamination. Modern baker’s yeast with uniform gassing powercould be shipped to bakers and kept for longer periods.
ConclusionsThis literature review on fermentation control indicates that
baker’s yeast technology developed as a large-scale industry withinabout 30 y, between 1910 and 1939, in parallel to the optimizationof growth media (Gelinas 2012). Nowadays, online processingcontrol tools are still searched for to further optimize the qualityof baker’s yeast. Surprisingly, several of the early key inventionsdisclosed in patents on the control of sugar concentration ingrowth media were later invalidated for want of novelty. After1940, this situation dismissed the true value of patents describingprocesses and probably encouraged trade secrets in the yeast sectorand other industries. Between 1900 and 2009, the main incentivesin the yeast industry were clearly to simplify the manufacturingprocess, to get the highest yields possible, to reduce costs, and toimprove gassing power of baker’s yeast. More effort was neededto improve yeast keeping properties and that essentially camethrough the development of active dry yeast.
Conflict of interestThere is no conflict of interest.
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