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PLEASE SCROLL DOWN FOR ARTICLE This article was downloaded by: [Instituto Politécnico Nacional][MRST Consortium] On: 23 November 2009 Access details: Access Details: [subscription number 916239063] Publisher Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37- 41 Mortimer Street, London W1T 3JH, UK Food Biotechnology Publication details, including instructions for authors and subscription information: http://www.informaworld.com/smpp/title~content=t713597251 Probiotics: An emerging food supplement with health benefits Renu Agrawal a a Department of Food Microbiology, Central Food Technological Research Institute, Mysore, Karnataka, India To cite this Article Agrawal, Renu'Probiotics: An emerging food supplement with health benefits', Food Biotechnology, 19: 3, 227 — 246 To link to this Article: DOI: 10.1080/08905430500316474 URL: http://dx.doi.org/10.1080/08905430500316474 Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
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Page 1: Probiotics: An emerging food supplement with health benefits

PLEASE SCROLL DOWN FOR ARTICLE

This article was downloaded by: [Instituto Politécnico Nacional][MRST Consortium]On: 23 November 2009Access details: Access Details: [subscription number 916239063]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Food BiotechnologyPublication details, including instructions for authors and subscription information:http://www.informaworld.com/smpp/title~content=t713597251

Probiotics: An emerging food supplement with health benefitsRenu Agrawal a

a Department of Food Microbiology, Central Food Technological Research Institute, Mysore,Karnataka, India

To cite this Article Agrawal, Renu'Probiotics: An emerging food supplement with health benefits', Food Biotechnology, 19:3, 227 — 246To link to this Article: DOI: 10.1080/08905430500316474URL: http://dx.doi.org/10.1080/08905430500316474

Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf

This article may be used for research, teaching and private study purposes. Any substantial orsystematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply ordistribution in any form to anyone is expressly forbidden.

The publisher does not give any warranty express or implied or make any representation that the contentswill be complete or accurate or up to date. The accuracy of any instructions, formulae and drug dosesshould be independently verified with primary sources. The publisher shall not be liable for any loss,actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directlyor indirectly in connection with or arising out of the use of this material.

Page 2: Probiotics: An emerging food supplement with health benefits

Food Biotechnology, 19:227–246, 2005Copyright © 2005, Taylor & FrancisISSN: 0890-5436 printDOI: 10.1080/08905430500316474

LFBT0890-54360000-0000Food Biotechnology, Vol. 19, No. 03, September 2005: pp. 0–0Food BiotechnologyProbiotics: An emerging food supplement with health benefitsProbioticsR. Agrawal

Renu Agrawal

Department of Food Microbiology, Central Food Technological Research Institute,Mysore, Karnataka, India

Probiotics are among the important functional foods. They comprise approximately65% of the world functional food market. Probiotic products are foods, which improveintestinal microflora and support good health of the consumer. The live bacteriapresent in the probiotic products are lactic acid bacteria, including Lactobacilli, Bifido-bacteria and Enterococci. Apart from health claims and maintenance of intestinalmicroflora, they protect against infections, alleviate lactose intolerance, reduce bloodcholesterol levels and also stimulate the immune system. The interactive researchbetween physiology, microbiology, food technology and molecular biology followed byclinical trials may produce a multi-functional probiotic strain for human consumption.

Key Words: Probiotic; lactic acid bacteria; functional food

INTRODUCTION

The world population is becoming more conscious of the relation betweennutrition and good health. This has stimulated increased research of the iden-tification of food and food components that have special benefits to the con-sumer. With these efforts, probiotic products have come into the market,which are identified as functional foods. These include foods containingphytochemicals, dietary fibre, structural lipids, bioactive peptides, polyunsat-urated fattyacids, etc. Prebiotics, probiotics and synbiotics (Holzapfel andSchillinger, 2002) are included in this category.

The probiotics are related to beneficial microorganisms. The term probi-otic has a number of definitions but widely accepted is that of Fuller (1989).According to him, “probiotics” are live microbial food supplements that benefi-cially affect the host animal by improving the intestinal microbial balance.

Address correspondence to Renu Agrawal, Department of Food Microbiology, CentralFood Technological Research Institute, Mysore, Karnataka, 570 013, India.E-mail: [email protected]

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The usefulness of lactic acid bacteria was first proposed by Metchnikoff(1908), who suggested that longevity was due to their high intake.

TAXONOMY OF PROBIOTIC MICROORGANISMS

Phylogenetic and genetic criteriaIt is early to make generalizations about probiotic performance on a scien-

tific basis, but it is generally assumed that probiotic properties are strain spe-cific. Hence, the need for strain identification and detection is very important(Brandt and Alatossava, 2003). Important genera that are employed for probi-otic purpose are generally Lactobacilli, Bifidobacteria and Enterococci.

Lactic acid bacteria (LAB) are gram positive, non-sporing, catalase nega-tive organisms that are devoid of cytochrome C and are non-aerobic, but areaerotolerant and acid tolerant. LAB can be divided into two physiologicalgroups: the heterofermentative LAB, which produce CO2, lactic acid, aceticacid, ethanol and mannitol from hexoses, and the homofermentative LAB,which produce primarily lactic acid from hexose (Kandler, 1983). Tradition-ally, LAB has been classified on the basis of phenotypic properties such asmode of glucose fermentation, growth at different temperatures, configurationof lactic acid produced (L/D)and fermentation of carbohydrates.

Holzapfel et al. (1997) and Klein et al. (1998) have dealt in detail about thetaxonomy and physiology of probiotic lactic acid bacteria. According to interna-tional standards, the probiotic cultures used in food should be well defined andcorrectly named according to valid taxonomic systems. The selection criteria forprobiotic microorganisms have been reviewed by Holzapfel et al. (2001). Phylo-genetic analysis was found not sufficient for a better characterization up to thestrain level. Here genetic methods play a very important role for further charac-terization. Holzapfel (1997) has dealt in detail with systematic identification ofprobiotic lactic acid bacteria with reference to phenotypic and genomic methods.These genomic methods have been applied with a good amount of success.

In genetic analysis, plasmid profiling was formerly preferred, but it wasfound that extra chromosomal DNA was unstable. Therefore, methods basedon chromosomal DNA were developed. These include restriction enzyme analy-sis (Ferrero et al., 1996), ribotyping (Rodtong, 1993), Randomly amplified poly-morphic DNA analysis (Duplessis, et al., 1995; Klijn et al., 1995; Collins et al.,1991; Erlandson and Bhatt, 1997) and gradient gel electrophoresis (Alatossava,2000; Walters et al., 2000). These workers have shown the efficacy of the geno-typic methods in strain identification. Pot et al. (1997) have studied taxonomyof microorganisms used as probiotics with the help of the above methods forspecies of Enterococci, Lactococci and Lactobacilli.

Charteris et al. (1997) and Simpson et al. (2001) demonstrated the selec-tive details, enumeration and identification of potential probiotic lactic acid

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bacteria, Bifidobacterium bifidum and other species. For a correct identifica-tion of lactic acid bacterial strain, it is essential to employ both phenotypicand genetypic methods. Lactobacillus casei, Lactobacillus paracasei andLactobacillus rhamnosus are mainly used as probiotics, whereas strains ofEnterococci are mainly used in nutrition. For phenotypic based criteria,important functions for consideration are carbohydrate fermentation pattern,resistance to different NaCl concentrations, growth on different nutrientmedia, growth at different temperatures and resistance against antibiotics.

Recently, molecular-based identification has been done by ribotyping(Zhong et al., 1998). In modern taxonomic phenotypic methods analysis of cellwall composition (peptidoglycan) and fermentation pathways of pentoses andhexoses are undertaken.

Lactobacillus and Bifidobacterium constitute a significant proportion of pro-biotic cultures used in developed countries. Although these two species havebeen isolated from different parts of the GI tract, the terminal ileum and colonappear to be the preferred sites. Species of Bifidobacterium are generally char-acterized as gram positive, non-spore forming, non-motile, catalase negativeand anaerobes. The enzyme fructose-6-phosphate phospho- ketolase, the keyenzyme of the glycolytic pathway, serves as a taxonomic character in identifyinggenera but does not enable inter-specific differentiation. At present, 29 speciesof Bifidobacteria genera are recognized, of which 10 are of human origin.

Differential detection and enumeration can be performed in a number ofways. Different plating media are employed which permit separate cultivationof each genus. In another method, a single plating medium is used that sup-ports the growth of designated genera. Final characterization consists ofsugar tolerance, nutritional requirement and antibiotic susceptibility. Moredetails are given by Charteris et al (1997), including a number of probes thathave been designed for Lactobacillus and Bifidobacterium species.

Klein et al. (1998) have used both phenotypic and genotypic methods fordetailed analysis of various probiotic bacteria. In order to see that probioticsshould not have any negative effect on the host, careful selection of the strainis very important. They show the importance of proper identification with thehelp of phenotypic and genotypic methods of application to differentiate vari-ous probiotic species.

In vitro studiesThe site of action of lactic acid bacteria and Bifidobacteria is the gas-

trointestinal tract. Before the organism reaches the gut, it has to pass throughthe stomach having approximately 2.5 litres of gastric juice (pH 2.0) secretionper day (Charteris et al., 1998). This usually causes destruction of most of themicroorganisms ingested. Therefore, the acid resistance property of probioticbacteria is of utmost importance and consideration. At the same time, the

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organism has to resist bile acids in the intestine and should adhere to theintestinal walls for its effectiveness. In order to achieve probiotic lactic acidbacteria with all these properties scientists are developing a keen interest ininducing these properties in lactic acid bacteria.

Towards this, Jacobson et al. (1999) studied 47 strains of Lactobacilli, observingthat 29 of them could survive a low pH (pH 2.5) for four hours and 16 strains grewwell with bile salts and oxgall. Only four strains were found to have strong adhesionto Caco-2 cells, whereas the rest exhibited mild adherence. The ability of each bacte-rium was found to be different and was strain specific (Kimoto et al., 1999).

Hamilton- Miller (2004) and Vinderola et al. (2003) made a comparativestudy on probiotic characteristics and biological barrier resistance in yogurt.Bernet et al. (1994) studied the mechanism involved in the adherence ofmicroorganism to intestinal epithelial cells. Gerriste et al. (1990) studied theproperties by oral administration of TNP-Lactobacillus conjugates in mice andevaluated mucosal and systemic immune responses and memory formation.Greene and Klaenhammer (1994) studied the factors involved in the adher-ence of Lactobacilli to human Caco-2 cells.

PROBIOTIC PRODUCTS

Probiotic organisms require a vehicle to reach the site of action in an activeform, which is the G.I. tract of the human body. The vehicle is generally a foodproduct, which contains these live bacteria. Scientific evidence suggests thatprobiotic bacteria consumed at a level of 109-1011 cfu/day can decrease theincidence and severity of some intestinal illnesses (Zubillaga et al., 2001).

The products should have a good shelf life and should have a cell counthigher than 106 cfu/ml till the end. The product should also go through theharsh conditions of gastric acid and bile salts before it reaches the G.I. tract,which is the site of action.At present, most of the individual probiotic foodsbelong to dairy products like yogurt, fermented milk and cheese (Table 1).

A number of new products based on cereals, fruits, vegetables and meat arein the development stages. These products have to undergo human trials before

Table 1: Probiotic products available in the market with lactic acid bacteria supplementation.

Product Bacteria

Yogurt Lactobacillus bulgaricus, Streptococcus thermophilus Lactobacillus casei and Bifidobacterium sp.

Kefir Lactobacillus sp. Lactococcus sp. Leuconostoc sp.Acidophilus milk Lactobacillus acidophilusFermented milk Enterococcus faecium Streptococcus thermophilusFermented vegetables Lactobacillus sp.

Adopted from E.R. Farmworth (2000).

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they are medically accepted. Gilliland et al. (2002) studied the viability of L. caseiand Bifidobacterium in yogurt-like products along with L. casei and B. longum. Itwas observed that pH influenced the survival rate in the products when stored at5° C for 35 days. Similar studies have been done by Schillinger (1999). Vinderolaet al. (2003) studied the behavior of Argentina yogurt and observed that full fatprobiotic yogurt (pH 4.5) was inhibitory when stored at 5° C for 4 weeks. A thor-ough study has been done by Ostlie et al. (2003) towards the growth and metabo-lism of selected strains of probiotic bacteria in milk. In a detailed study ofdifferent probiotic milk products, Hattingh and Viljoen (2001) noticed that thesurvival of microbes was dependent on various factors like the strain used, inter-action between species present in the product and culture conditions.

Among milk products, the main probiotic carriers in foods are yogurt, fer-mented milk and cheese. A number of reviews are available on the health ben-efits of the consumption of fermented dairy products (Dave and Shah, 1997;Kurman and Rasie 1991).

It is generally assumed that consumption of probiotic yogurt should be morethan 100 g/day containing more than 106 Cfu/ml (Rybka and Kailaspathy, 1995). Inrecent years, there has been a significant increase in the popularity of yogurtemphasizing the incorporation of L. casei and B. bifidum. The conventional yogurtstarter bacteria L. bulgaricus and St. thermophilus lack the ability of surviving thepassage through the G.I. tract and consequently do not play a role in the human gut.

Hattingh and Viljoen (2001) reviewed the role of yogurt as a probioticcarrier food. The consumption of probiotic products is helpful in controllingintestinal diseases (Mittal and Garg, 1992). Besides yogurt, other probioticproducts are fermented milk (Nighswonger et al., 1996), beverages and probi-otic cheese (Gomes et al., 1995), Cotton cheese (Blanchette et al., 1995), pow-dered milk, cookies and ice creams (Hekmat and Mc Mohan, 1992) and dairydesserts (Laroia and Martin, 1991; Anandan et al., 1999). Cheddar cheese hasbeen shown to be an effective vehicle for the delivery of some probiotic organ-isms, especially L. paracasei. Cheese has a higher pH than yogurt and fer-mented milk and hence can support survival of probiotic bacteria for a longerduration (Gardiner et al., 1998). Dinaker and Mistry (1994) studied thegrowth and viability of Bifidobacterium bifidum in cheddar cheese. Accordingto them, viability of this organism in products over a long shelf life at refriger-ation temperature is not satisfactory. The low pH of fermented milk and theaerobic conditions of packaging are not conducive for their survival. In theirstudy the organisms were viable during 24 weeks of study.

Non-milk probiotic productsBesides milk-based probiotic products, attempts are being made to

develop non-milk probiotic products (Molin, 2001) mainly for the treatment of

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lactose intolerance and control of cholesterol levels which is a drawback inmilk based products.

Arihara and Itoh (2000) have isolated UV induced L. gasseri mutants thatare resistant to NaCl and sodium nitrite. These can be used as starter culturefor the preparation of probiotic meat products. As this organism is dominantlyfound in the human intestinal tract it may be an appropriate probiotic starterculture for meat fermentations.

Papamanoli et al. (2003) isolated lactic acid bacterial strains from fer-mented sausages, which can be used as starter cultures for the preparation ofmeat fermentations. They found that traditionally prepared sausages withlong ripening time have better sensory qualities than when a UV inducedmutant strain was used. After the fermentation they isolated the culturestrains, and found that 90% belonged to Lactobacillus.

Fermented Milk ProductsAccording to Nighswonger et al. (1996), L. casei and L. acidophilus survive

better in cultured buttermilk than in yogurt. Ostlie et al. (2003) studied thecell count in milk which was above 8.7–9.18 log cfu/ml after 6–16 h of incuba-tion. According to Sodini et al. (2002), the addition of casein hydrolysate to amilk product gave it a good taste and improved the flavor.

Hattingh and Viljoen (2001) made a detailed study of milk products withprobiotics, concluding that the survival of microbes depends on various factorssuch as strains used, interaction between species, culture conditions, growthpromoters and inhibitors, etc. When children were fed with probiotic curd, theincrease in body weight was found to be much higher at the end of 90 days ascompared with controls. Also, the incidence of diarrhea was found to be reduced.

ENCAPSULATION OF PROBIOTICS

Encapsulation is a new technology being applied to increase the storage life ofthe probiotic product. Betoret et al. (2003) have developed apple cylindersimpregnated with apple juice containing L. casei. Samples were air dried at40° C to a water content of 0.037 Kg water/kg product and stored at ambienttemperature for two months. At the end of this period viability of cells in theproduct was 106 Cfu/g.

Cruce and Goulet (2001) have also suggested microencapsulation asaffording protection to products containing LAB. Certain protective agentslike sugars, sugar alcohols, milk, starch, maltodextrin and N2 flushing areknown to enhance the ability of microorganisms to survive.

According to Hansen et al. (2002), however, encapsulation was not verysuccessful as it resulted in off-flavor in some cases. Fito et al. (2001) have triedto use the methodology for incorporation of active components such as prebiotics,

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dietary fibres and plant sterols. In their study Cruce and Goulet (2001)reported that in non-fat dry milk the stability after a shelf life of 4 months at30° C of microencapsulated P. acidilactici was 69%, while that of a standardfreeze-dried product (probiotic powder) was only 15%. This technology prom-ises to be of great help in increasing the survival rate of probiotics and shouldsee much more developments in the coming years.

CLINICAL STUDIES

This is an area of probiotic therapy that requires detailed attention. If thestudies are carried out systematically, they will prove useful in the treatmentof various clinical disorders such as different types of diarrhea, gastrointesti-nal disorders and cholesterol levels in the blood. This aspect is different fromthe one where probiotics are used for the well being; the latter does notrequire a medical prescription. Probiotics are also used for their immunologi-cal and anti-microbial properties. There are many reports in the literatureregarding clinical trials but most of the studies did not have proper controlslike blindfold studies and therefore could not be taken ahead.

Farmworth (2000), Tamboli et al. (2003), Bengmark (2003), Surawicz(2003) and Marteau (2003) have reviewed the medical studies carried outrecently with proper controls.

STUDIES WITH DIFFERENT TYPES OF DIARRHOEA

1. Infantile diarrheaThe most common cause of diarrhea in children is rotavirus infection.

Savedra et al. (1994) randomized 55 children in the age group of two yearstreated with B. bifidum and St. thermophilus in milk fermentations. The over-all rate of diarrhea was reduced in the treated group. Other workers have alsoconfirmed the usefulness of probiotics in infantile diarrhea (Isolauri et al.,1991; Oberhelman et al., 1999).

2. Studies with traveler’s diarrheaThese studies have not been equivocal (Hilton et al., 1997; Black et al.,

1989). It is not possible to compare the results of one strain to another, asmechanisms underlying clinical effects are not clearly understood.

3. Antibiotic associated diarrhea (AAD)Siitonen et al. (1990) reviewed the use of probiotics like Lactobacillus

rhamnosus G.G and the yeast Saccharomyces boulardii in antibiotic-associated

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diarrhea. Both microorganisms were found effective. It is felt that morecontrolled studies and safety trials are required before this treatment isaccepted. Mc Farland et al. (1995) and Tankanow et al. (1990) found positiveresults in patients suffering with AAD, although Barlett et al. (1980) did notnotice any encouraging results. It is therefore felt that much more work has tobe done with travelers’ and antibiotic associated diarrhea except infantilediarrhea, which is caused by rotavirus.

Inflammatory Bowel Disease (IBD)Tamboli (2003) and Martin (2005) reviewed the effect of probiotics in IBD.

The pathogenesis of IBD is not clearly understood. Intestinal microorganismsas mediator of this inflammation are receiving increasing attention. Studies ofhost-microbe interactions have provided support for probiotic therapy in IBD.

Many workers (Kruis et al., 1997) have studied the effect of mesalamineand compared it with an E. coli strain. After 12 weeks of therapy about 11–16%patients had relapse in both groups. In a randomized trial, non-pathogenicE. coli treatment was compared with mesalamine therapy for treating ulceritiscolitis. Remission in both the groups was around 70% (Rembaekan et al., 1999).

The numbers of trials conducted over a period do not give a clear-cutpicture about the utility of probiotics in ulceritis colitis treatment. Reid et al.(1995, 1998) have observed the prevention of urinary tract microbial infec-tions when Lactobacilli strains were instilled.

Critically ill patientsProbiotics and prebiotics have been shown to reduce the rate of infection

in sick and postoperative patients. Compounds such as antibiotics and phar-macological agents have detrimental effects on mucosal flora and immune sys-tems. Recent studies in patients with severe and acute pancreatitis abdominalsurgery and liver transplant patients have shown some beneficial effects withthe use of probiotic Lactobacillus plantarum 299V along with oral fibre as aprebiotic (Olah et al., 2002). In another study of abdominal surgery patients,when L. plantarum 299V was fed with oat fibre, no significant differenceswere found as compared with the control possibly due to the low level of lacticacid bacteria and oat fibre employed in the study.Bengmark (2003) and Edgar(2005) has reviewed the use of probiotics in many other surgical cases.

Immune SystemsRecently, Gill et al. (2000) have shown that probiotics enhance natural

immune functions by dietary consumption of L. lactis. According to Schiffrinet al. (1995), it appears that the cultured strain may adhere transiently andcolonize the GI tract, ultimately increasing the IgA levels. Isolauri et al.

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(2001) proposed that many probiotic effects are modulated through immuneregulation of pro and anti-inflammatory cytokines. Similarly probiotic inges-tion is reported to stimulate cytokine production in blood cells.

Antimicrobial PropertiesWith the emergence of antibiotic resistant microorganisms, the concept of

probiotic therapy is gaining ground. The lowering of pH by acids like lacticacid and acetic acid has bacteriocidal and bacteriostatic effects. In addition,they also produce H2O2 and bacteriocins. Kasper (1998) demonstrated antimu-tagenic properties by acids produced against a number of mutagenic com-pounds. Guarner (2003) and Tuohy et al. (2003) have shown that LABingestion reduced the activity of enzymes like β-glucoronidase, nitro reductaseand azoreductase which transform precarcinogen into active form. Lactic acidbacteria are useful in the promotion of human health.

According to medical experts correct identification of the strains withmedical evidence along with clinical trials will allow the authorities to recom-mend them for therapeutic purposes.

SAFETY ASPECTS OF PROBIOTICS

Most probiotics are marketed as ingredients of foodstuff or drugs, while othersare sold in the live form as freeze dried powders, tablets or capsules. Hence,consideration of safety of these microorganisms or products is of utmostimportance, as they are being used for human consumption. According toGasser (1994) many lactic acid bacterial strains have been isolated frombloodstream infections and local infections. Aguirre and Collins (1993)reported lactic acid bacteria from infection sites; these reports ensure thesafety of lactic acid bacteria as probiotics.

Adams and Marteau (1995) have tested the safety of lactic acid bacteria byin vitro methods, animal studies and human clinical studies.

Factors involved in safety considerationsStrains of LAB found in the intestinal microflora are preferentially used

as probiotics. Knowledge of their reactions in the intestinal microbial associa-tion has to be increased (Darla et al., 2005). It is necessary to understand theecological performance of these probiotic strains.

Prebiotics

A prebiotic is defined as non-digestable food ingredient that beneficiallyaffects the host by selectively stimulating the growth and activity of a numberof bacteria in the colon, improving the host’s health. Commercially available

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prebiotics are fructooligosaccharides (FOS), insulin, lactulose and galactooli-gosaccharides. Prebiotics mainly help the individuals with low levels of Bifido-bacteria in the elderly (Tuohy, 2001). He observed the beneficial effects in themodulation of gut microflora. The prebiotic effect has been studied in humanclinical trials by feeding biscuits containing partially hydrolysed guar gumand fructooligosaccharides. Although there is no recommended daily dose ofprebiotics, a report by Roberfroid et al. (1988) suggests a daily dose of 4g/dayof insulin or FOS to increase gut Bifidobacteria.

Rastall and Gibson (2002) have shown the natural presence of prebiotics inbreast milk and vegetables such as Jerusalem artichokes and onions. Hamilton(2004) has written a review of clinical trials for benefits from prebiotics and pro-biotics to elderly populations helpful in malnutrition, lactose intolerance, cal-cium absorption and constipation. Pool-zobel et al. (2002) found that insulin andFOS reduced the number and size of precancerous lesions as well as tumor inci-dence in carcinogen-treated rats. Roberfroid (2000) linked prebiotics to anenhancement of mineral absorption in the large bowel.

A synbiotic approach (a mixture of probiotics and prebiotics) has shownbeneficial results. Kiebling et al. (2002) have shown that long-term (7 weeks)consumption of synbiotic yogurt (L. acidophilus 145, B. longum 193 + FOS)led to significant effects in LDL/HDL cholesterol ratios in 29 healthy women.Despite the numerous studies and human clinical trials, there is still a gap inour knowledge of the metabolic pathways taken by prebiotics and probiotics.Safety is also required for prebiotics, which are frequently used with probiot-ics. If the prebiotic is a traditional food or a food component, there is no con-cern. Hammes and Hertel (2002) have given some details about the safetyaspects of LAB used as probiotics. According to them, the intestinal microfloramay exhibit properties in foods that are not revealed in the intestinal tract. Itis possible that LAB may have pathogenic potential, as reports in the litera-ture indicates for their involvement in human infection. According to Linket al. (1994), changes in intestinal flora with intake of fermented milk havebeen reported. It is recorded that strains of Enterococci are involved in humaninfections. Because of these observations, doubts have been raised as towhether Enterococci can be classified as safe probiotics (Aguirre and Collins,1993). Ishibashi and Yamaguchi (2001) have written an excellent review onprobiotics and safety, in which they covered various aspects such as absence ofpathogenicity and infectivity as a requisite for probiotic safety and enzymaticactivity associated with production of harmful substances.

MARKET POTENTIAL OF PROBIOTICS

Like acceptance of any product in the market, it should be realized thatincreased consumption is dependent on many factors. As more and morepeople are becoming health conscious, the sales of probiotics is increasing.

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Manufacturers are aware of this and are trying to get newer products into themarket. Since these are edible products, the foremost requirement is that theprobiotic product should be sensorily acceptable and liked by people.

The concept of probiotics for improving the health status of an individualwas developed in Japan in the 1980s. In the last ten years the probiotic prod-ucts mainly being dairy products have established themselves in Europe andin the USA. There is not much literature on probiotic consumption in develop-ing countries.

The problem with probiotic preparations is that in many productsalthough the addition of lactic acid bacteria is mentioned, the particularstrain used is not mentioned. According to Klein (1999), it is very important toknow whether all the strains of LAB or bifidobacteria are useful as probiotics.

PROBIOTIC CONSUMPTION AROUND THE WORLD

Japan: A product “Yakult” consisting of bifidobacterial strains, whey, miner-als and dietary fibre had sales of more than 11 trillion yen. In addition, fer-mented milk drinks are in great demand (Arunachalam, 1999). According tothe literature, the market in Japan for probiotics and other functional foods isapproximately $ 3.5 billion.

Europe: In Europe (1997), 65% of functional food market consists of probi-otic products of $890 million. The yogurt market is worth $600 million. Yogurtwith live lactic acid bacteria is on the forefront with its acceptable taste andflavor.

Consumers are mostly concerned with health problems such as osteoporo-sis, cholesterol level in serum, heart diseases and general well being. Hence,products should be available for treating them. A survey in Europe (1997)indicated that more than 97% of consumers look for healthier food.

U.S.A.: The labeling requirement of probiotic food products is less as com-pared with Japan and Europe. However, strong medical claims are notallowed without strong clinical data. “Acidophilus yogurt” is on the forefrontamong probiotic products.

Overall, enough evidence is available to indicate beneficial effects of probi-otic products on good health. The increase in sales in this direction shows thegrowing health consciousness of people. More data are necessary to determinethe medical benefits and claims for better health.

It is expected that in the first decade of the twenty-first century the globalmarket for probiotic foods will be around $17 billion. Stanton et al. (2001) dis-cussed about the various probiotic products and the different companies deal-ing with it. Currently, most of the products are milk products; new productsare being investigated with base as fruit juices or fermented whey (Calvoet al., 2002). Arihara and Itoh (2000) studied the importance of probiotics inmeat products to be utilized for large-scale preparation.

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LABELING OF COMMERCIAL PROBIOTICS

In veterinary and human medicine, probiotic therapy is becoming very impor-tant, and many probiotic products are available commercially. Although probi-otics are mainly food supplements they are not regulated for efficacy andquality control. In a survey examining the labels of 44 probiotic products,Weese (2003) observed that labeling on 44% of the products was improper, asmost of them did not contain the stated number of organisms (Weese, 2002).According to Weese (2003), a probiotic label should state the organism uptostrain level, correctly spelled, and also state the number of live organism untilthe expiry of the shelf life. To date, none of the products in the market fulfillall these criteria. Also, the product should be scrutinized by the veterinarypractitioners like any other pharmaceutical products. There is much scope forresearch and development in this line, as proper labeling will help in theprevention and treatment of many diseases in a natural way.

GENERAL HEALTH BENEFITS BY PROBIOTICS

Probiotics have shown their potential in the prevention of certain diseases andalso promoting specific aspects of health. They are helpful in improving prob-lems of malnutrition, lactose intolerance, calcium absorption and constipation(Hamilton-Miller, 2004; Groote et al., 2005). The gut microbiota plays animportant role in human health and disease by preventing the colonization ofpathogenic microorganisms (Tuohy et al., 2003). A range of probiotic strainshave been evaluated for their antidiarrheal capabilities (Isolauri, 1991), pre-vention of colorectal cancer (CRC) and chronic mucosal inflammation (IBD) bya non-pathogenic strain of E. coli (Rembacken et al., 1999). Many probioticshave shown to lower the activity of β-glucuronidase, β-glycosidase, azoreduc-tase and nitroreductase, which are known to convert precarcinogens to carcin-ogens (Burns and Rowland, 2000). Probiotics have also been shown to liberatelow molecular weight peptides in G.I tract and trigger the immune system(Isolauri et al., 2001). There is currently a concerted effort in Europe to studythe gaps in knowledge concerning the medical efficacy and mechanistic princi-ples of microbiota using probiotics, prebiotics and synbiotics (Mattila-Sandholmet al., 2003). All these studies have enhanced the general health of humanbeings and reduced the onset of diseases.

FUTURE DEVELOPMENTS

If probiotics are to represent a real and effective alternative to antibiotics andchemotherapeutics, much more work is required to select LAB strains withstrong probiotic effects, and methods should be developed to ensure maximumefficacy of probiotic at the time of consumption. Food companies will continue

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to research new functional food products with health claims. Product launchesin areas like probiotic food products, fortified foods and drinks see a lot offuture. Of course, the market growth will depend on scientific substantiation.

The rate of increase in resistance to antibiotics is a major public healthproblem all over the world (Neu, 1994; Bengmark, 1998). Hence, natural alter-natives are becoming more attractive. In fact, the World Health Organizationrecommends a global programme to reduce the use of antibiotics.

The clinical use of probiotics showed suppression of pathogens, givingevidence for their consumption in inhibiting the growth of enteropathogens(Gousalez et al., 1993, Drago et al., 1997; Hudault et al., 1997). In addition, thedata collected suggest the potential use of probiotics in preventing urino genitaltract microbial infections (Reid et al., 1995, 1998).There is a need to work outthe use of probiotics as alternatives to antibiotics in animals and poultry.

With the advances in sequencing and bioinformatics technology, genome-sequencing projects will be looked into in the near future for probiotic micro-organisms. According to Tamboli (2003), the development of probiotics capableof effectively delivering cytokinin therapy is a major advancement in biologicaltherapy to IBD. The use of genetically modified organisms in humans maytake some time for their application. Bengmark (2003) has emphasized the useof a probiotic consortium. It is expected that strong clinical efficiency can beachieved in the future by the use of probiotic LAB consortiums with severalbioactive properties.

According to Surawiz (2003), the population of high risk AAD should beidentified before widespread use of probiotics is undertaken. Also, there isneed for well-controlled trials of efficacy with adequate safety studies.

In spite of numerous feeding studies showing positive effects on health,there is limited understanding concerning the mechanism of probiotic activityin vivo. Modern high-resolution molecular techniques based on the phyloge-netic information encoded by 16S rRNA gene are being applied to characterizethe gut microflora within different disease strains. This is likely to bypass theinherent limitations of lack of selective growth media and uncontrollable bac-teria. Recently, in Europe, a number of European Union projects have beenfunded to identify the mechanisms through which pro-, pre- and synbioticscan improve host health.

According to Steidler (2003), it is possible through genetic engineering toimprove the existing strains and also to create completely new probiotics. Thisis possible with thorough knowledge of metabolic reactions in various probiot-ics. The metabolism of microorganisms can be modified through the integra-tion of foreign enzymes. Paton et al. (2001) have already constructed an E. colistrain that could answer the need for therapeutics to counteract intestinalinfection with Shigella toxin producing bacteria.

It must be realized that for current genetically modified (GM) probiotics,biological safety has to be assured. Also, the uninhibited spread of GM

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microorganisms in the environment is highly undesirable. Thus, biosafety ofthe strains produced has to be thoroughly investigated. Steilder (2003) in hisreview has given details of application of GM probiotics under various clinicalconditions.

CONCLUSIONS

Since there is substantial demand for natural treatments with respect to vari-ous diseases, probiotics are gaining importance. Moreover, improved func-tional characteristics of milk products could be potentially achieved byaltering the aminoacid sequence. Targets for modification include α-lactoalbumin,β-interferon, γ- interferon, factor IX, protein C, serum albumin superoxidase,lactoferrin, lyzozyme and immunoglobulins (Mathur et al., 2003). To capitalizeon this emerging knowledge better molecular and metabolic studies of bacte-ria from infection sites and the ones used for probiotics are essential (Saxelinet al., 1996). Further understanding the expression of novel disease-protectiveproteins in probiotic systems could be an attractive solution for diseasemanagement through the diet.

ACKNOWLEDGEMENT

I express my gratitude to Dr. V. Prakash, Director, CFTRI. I thankDr. S. Umesh, HOD, Food Microbiology for encouragement. I thankDr. M.V. Patwardhan for discussions and Shobha Rani. P for assistance.

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