Department of Chemical Engineering National Institute of
Technology Rourkela 2008
HYDROLYSIS OF LIGNOCELLULOSIC MATERIALS FOR ETHANOL
PRODUCTION2008-09
A thesis submitted in partial fulfillment of the requirements
for the degree of Bachelor of Technology in Chemical Engineering By
Nirbhay Gupta Roll no. 10500027 Under guidance of
1
National Institute of Technology Rourkela
CERTIFICATE
This is to certify that the thesis entitled HYDROLYSIS OF
LIGNOCELLULOSIC MATERIALS FOR ETHANOL PRODUCTION submitted by Mr.
Nirbhay Gupta in partial fulfillments for the requirements for the
award of Bachelor of Technology Degree in Chemical Engineering at
National Institute of Technology, Rourkela is an authentic work
carried out by him under my supervision and guidance. To the best
of my knowledge the matter embodied in the thesis has not been
submitted by any other University/Institute for the award of any
Degree or Diploma.
Date:
Dr. A. KumarDepartment of Chemical Engineering National
Institute of Technology Rourkela-769008
2
ACKNOWLEDGEMENT
I would like to make my deepest appreciation and gratitude to
Prof. A. Kumar for his invaluable guidance, constructive criticism
and encouragement during the course of this project.
I would like to thank Prof. R.K.Singh for being a uniformly
excellent advisor. He was always open minded, helpful and provided
us with a strong broad idea.
Grateful acknowledgement is made to all the staff and faculty
members of Chemical Engineering Department, National Institute of
Technology, Rourkela for their consistent encouragement.
In spite of the numerous citations above the author accepts full
responsibility for the contents that follow.
DATE:
Nirbhay Gupta Roll: 10500027
3
CONTENTSContents List of figures List of Tables Abstract vi v
iii v
Chapter 1
INTRODUCTION
1
Chapter 22.1 2.2
LITERATURE REVIEWEthanol from Cellulose Ethyl Alcohol:
Overview
34 7
Chapter 33.1
PRODUCTION METHODS Pretreatment of lignocellulosic materials
12 13 14 14 17 18
3.2 Physical Pretreatment 3.3 Chemical Pretreatment 3.4
Biological Pretreatment 3.5 Hydrolysis Process
Chapter 4
MATERIALS & EQUIPMENT USED 4.1 Materials Used 4.2 Equipments
Required
21 22 22
4
Chapter 5
PROCEDURE OF EXPERIMENT 5.1 Pretreatment of bagasse 5.2
Hydrolysis 5.3 pH adjustment 5.4 Fermentation
25 26 26 27 27
Chapter 6
RESULTS 6.1 Standard plot for ethanol 6.2 Analysis of ethanol
for different days 6.3 Comparison of ethanol concentration with
increasing no. of days.
29 30 33
40
Chapter 7
DISCUSSION
43
Chapter 8
REFERENCES
45
5
LIST OF GRAPHS 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11
Standard plot for ethanol Absorbance vs Molarity curve for day 1
Absorbance vs Molarity curve for day 2 Absorbance vs Molarity curve
for day 3 Absorbance vs Molarity curve for day 7 Absorbance vs
Molarity curve for day 8 Absorbance vs Molarity curve for day 9
Absorbance vs Molarity curve for day 10 Ethanol conc. Vs no. of
days curve for 0.2 M Ethanol conc. Vs no. of days curve for 0.3 M
Ethanol conc. Vs no. of days curve for 0.5 M 32 33 34 35 36 37 38
39 40 41 42
LIST OF TABLES
6.1 6.2 6.3-6.9 6.10 6.11 6.12
Standard data for ethanol concentration Standard for ethanol
concentration (revised) Data for molarity vs absorbance for 10 days
Ethanol conc. Vs no.of days table for 0.2 M Ethanol conc. Vs no. of
days table for 0.3 M Ethanol conc. Vs no. of days table for 0.5
M
30 31 33-39 40 41 42
6
ABSTRACT
PURPOSE OF THE PROJECTBiofuel is defined as solid, liquid or
gaseous fuel derived from relatively recently dead biological
material and is distinguished from fossil fuels, which are derived
from long dead biological material. Theoretically, biofuels can be
produced from any carbon source; although, the most common sources
are photosynthetic plants. Various plants and plant-derived
materials are used for biofuel manufacturing. Increasing the use of
bio-fuels for energy generation purpose is of particular experiment
nowadays because they allow mitigation of greenhouse gases, provide
independence and even may offer new employment possibilities.
Bio-fuels are being investigated as potential substitutes for
current high pollutant fuels obtained from conventional sources.
There are two common strategies of producing liquid and gaseous
agrofuels. One is to grow crops high in sugar, and then use yeast
fermentation to produce ethyl alcohol. The second is to grow plants
that contain high amounts of vegetable oil, such as oil palm,
soybean, and algae. When these oils are heated, their viscosity is
reduced, and they can be burned directly in a diesel engine, or
they can be chemically processed to produce fuels such as
biodiesel.
BREIF DESCRIPTION OF THE EXPERIMENTThe raw material used for the
experiment is bagasse. First the bagasse is chipped and grinded
(may be up to powder form). Then this is taken for acid hydrolysis.
Dilute sulphuric acid of 0.2 M, 0.3 M, and 0.5 M concentration were
used in this process. For the acid hydrolysis, 5 gms of bagasse was
put in 100 ml of each of the concentrations and was allowed to soak
for 1 day. Then it was autoclaved for half an hour and allowed to
cool. The fermentation media was prepared. 5 gms of yeast was added
to the above media and kept in incubator for 1 day. 10 ml of this
media was added to each of the sample in asceptical (laminar flow
hood) manner and placed in orbital shaking incubator. The pH was
adjusted to 5 and the fermenting temperature was kept at 35 0C.
Fermentation may take up to 10 days.
7
Chapter 1
INTRODUCTION
8
Energy consumption has increased steadily over the last century
as the world population has grown and more countries have become
industrialized. Crude oil has been the major resource to meet the
increased energy demand. Scientists used several different
techniques to estimate the current known crude oil reserves and the
reserves as yet undiscovered and concluded that the decline in
worldwide crude oil production will begin before 2010. They also
predicted that annual global oil production would decline from the
current 25 billion barrels to approximately 5 billion barrels in
2050. Because the economy in the US and many other nations depends
on oil, the consequences of inadequate oil availability could be
severe. Therefore, there is a great interest in exploring
alternative energy sources Unlike fossil fuels, ethanol is a
renewable energy source produced through fermentation of sugars.
Ethanol is widely used as a partial gasoline replacement in the US.
Fuel ethanol that is produced from corn has been used in gasohol or
oxygenated fuels since the 1980s. These gasoline fuels contain up
to 10% ethanol by volume. As a result, the US transportation sector
now consumes about 4540 million liters of ethanol annually, about
1% of the total consumption of gasoline. Recently, US automobile
manufacturers have announced plans to produce significant numbers
of flexible-fueled vehicles that can use an ethanol blend E85 (85%
ethanol and 15% gasoline by volume) alone or in combination with
gasoline. Using ethanol-blended fuel for automobiles can
significantly reduce petroleum use and exhaust greenhouse gas
emission. However, the cost of ethanol as an energy source is
relatively high compared to fossil fuels. A dramatic increase in
ethanol production using the current cornstarch-based technology
may not be practical because corn production for ethanol will
compete for the limited agricultural land needed for food and feed
production. A potential source for low-cost ethanol production is
to utilize lignocellulosic materials such as crop residues,
grasses, sawdust, wood chips, and solid animal waste.
9
Chapter 2
LITERATURE REVIEW
10
Cellulose molecules consist of long chains of glucose molecules
as do starch molecules, but have a different structural
configuration. These structural characteristics plus the
encapsulation by lignin makes cellulosic materials more difficult
to hydrolyze than starchy materials. Hemicellulose is also
comprised of long chains of sugar molecules; but contains, in
addition to glucose (a 6-carbon or hexose sugar), contains pentoses
(5-carbon sugars). To complicate matters, the exact sugar
composition of hemicellulose can vary depending on the type of
plant. Since 5-carbon sugars comprise a high percentage of the
available sugars, the ability to recover and ferment them into
ethanol is important for the efficiency and economics of the
process. Recently, special microorganisms have been genetically
engineered which can ferment 5-carbon sugars into ethanol with
relatively high efficiency 2.1 ETHANOL-FROM-CELLULOSE In times of
fuel shortages, fermentation ethanol has been commercially
manufactured in the US from cellulosic biomass feedstock using acid
hydrolysis techniques. However, it is only recently that
cost-effective technologies for producing ethanol-from-cellulose
(EFC) in the US have started to emerge. There are three basic types
of EFC processesacid hydrolysis, enzymatic hydrolysis, and thermo
chemicalwith variations for each. The most common is acid
hydrolysis. Virtually any acid can be used; however, sulfuric acid
is most commonly used since it is usually the least expensive
11
12
13
2.2 ETHYL ALCOHOL: OVERVIEW Ethanol, also called ethyl alcohol,
pure alcohol or drinking alcohol, is a volatile, flammable,
colorless liquid. It is a psychoactive drug, best known as the type
of alcohol found in alcoholic beverages and in modern thermometers.
Ethanol is one of the oldest recreational drugs known to man. In
common usage, it is often referred to simply as alcohol or spirits.
Ethanol has widespread use as a solvent of substances intended for
human contact or consumption, including scents, flavorings,
colorings, and medicines. In chemistry, it is both an essential
solvent and a feedstock for the synthesis of other products. It has
a long history as a fuel for heat and light and also as a fuel for
internal combustion engines.Properties Molecular formula Molar mass
Appearance Density
C2H6O 46.07 g mol1 colorless clear liquid 0.789 g/cm3 114.3 C,
159 K, 174 F 78.4 C, 352 K, 173 F
Melting point
Boiling point Solubility in water Acidity (pKa)
Fully miscible
15.9 1.200 mPas (cP) at 20.0 C
Viscosity
Dipole moment
5.64 fCfm (1.69 D) (gas
14
2.2.1 PHYSICAL PROPERTIES Ethanol is a volatile, colorless
liquid that has a strong characteristic odor. It burns with a
smokeless blue flame that is not always visible in normal light. It
is also used in finger nail polish remover. The physical properties
of ethanol stem primarily from the presence of its hydroxyl group
and the shortness of its carbon chain. Ethanols hydroxyl group is
able to participate in hydrogen bonding, rendering it more viscous
and less volatile than less polar organic compounds of similar
molecular weight. Ethanol is a versatile solvent, miscible with
water and with many organic solvents
2.2.2 CHEMICAL PROPERTIES Ethanol is classified as a primary
alcohol, meaning that the carbon to which its hydroxyl group is
attached has at least two hydrogen atoms attached to it.
2.2.2.1 Acid-base chemistryEthanol's hydroxyl group causes the
molecule to be slightly basic. It is almost neutral like water. The
pH of 100% ethanol is 7.33, compared to 7.00 for pure water.
Ethanol can be quantitatively converted to its conjugate base, the
ethoxide ion (CH3CH2O), by reaction with an alkali metal such as
sodium: 2CH3CH2OH + 2Na 2CH3CH2ONa + H2, or a very strong base such
as sodium hydride: CH3CH2OH + NaH CH3CH2ONa + H2. This reaction is
not possible in an aqueous solution, as water is more acidic, so
that hydroxide is preferred over ethoxide formation.
15
2.2.2.2 HalogenationEthanol reacts with hydrogen halides to
produce ethyl halides such as ethyl chloride and ethyl bromide:
CH3CH2OH + HCl CH3CH2Cl + H2O HCl reaction requires a catalyst such
as zinc chloride. Hydrogen chloride in the presence of their
respective zinc chloride is known as Lucas reagent. CH3CH2OH + HBr
CH3CH2Br + H2O HBr requires refluxing with a sulfuric acid
catalyst. Ethyl halides can also be produced by reacting ethanol
with more specialized halogenating agents, such as thionyl chloride
for preparing ethyl chloride, or phosphorus tribromide for
preparing ethyl bromide. CH3CH2OH + SOCl2 CH3CH2Cl + SO2 + HCl
2.2.2.3 Haloform reactionThe haloform reaction is a chemical
reaction where a haloform (CHX3, where X is a halogen) is produced
by the exhaustive halogenation of a methyl ketone (a molecule
containing the R-COCH3 group) in the presence of a base.
2.2.2.4 Ester formationUnder acid-catalyzed conditions, ethanol
reacts with carboxylic acids to produce ethyl esters and water:
RCOOH + HOCH2CH3 RCOOCH2CH3 + H2O. For this reaction to produce
useful yields it is necessary to remove water from the reaction
mixture as it is formed.
16
Ethanol can also form esters with inorganic acids. Diethyl
sulfate and triethyl phosphate, prepared by reacting ethanol with
sulfuric and phosphoric acid respectively, are both useful
ethylating agents in organic synthesis. Ethyl nitrite, prepared
from the reaction of ethanol with sodium nitrite and sulfuric acid,
was formerly a widely-used diuretic.
2.2.2.5 DehydrationStrong acid desiccants, such as sulfuric
acid, cause ethanol's dehydration to form either diethyl ether or
ethylene: 2 CH3CH2OH CH3CH2OCH2CH3 + H2O CH3CH2OH H2C=CH2 + H2O
Which product, diethyl ether or ethylene, predominates depends on
the precise reaction conditions
2.2.2.6 OxidationEthanol can be oxidized to acetaldehyde, and
further oxidized to acetic acid. In the human body, these oxidation
reactions are catalyzed by enzymes. In the laboratory, aqueous
solutions of strong oxidizing agents, such as chromic acid or
potassium permanganate, oxidize ethanol to acetic acid, and it is
difficult to stop the reaction at acetaldehyde at high yield.
Ethanol can be oxidized to acetaldehyde, without over oxidation to
acetic acid, by reacting it with pyridinium chromic chloride.[19]
The direct oxidation of ethanol to acetic acid using chromic acid
is given below. C2H5OH + 2[O] CH3COOH + H2O The oxidation product
of ethanol, acetic acid, is spent as nutrient by the human body as
acetyl CoA, where the acetyl group can be spent as energy or used
for biosynthesis.
2.2.2.7 ChlorinationWhen exposed to chlorine, ethanol is both
oxidized and its alpha carbon chlorinated to form the compound,
chloral. 4Cl2 + C2H5OH CCl3CHO + 5HCl
17
2.2.2.8 CombustionCombustion of ethanol forms carbon dioxide and
water: C2H5OH(g) + 3 O2(g) 2 CO2(g) + 3 H2O(l); (Hr = 1409
kJ/mol[21])
18
Chapter 3
PRODUCTION METHODS
19
The basic five stages of this process are: 1. A pre- treatment
phase to make the raw material such as wood or straw amenable to
hydrolysis. 2. Hydrolysis, to break down the molecules of cellulose
into sugars. 3. Separation of the sugar solution from the residual
materials, notably lignin. 4. Yeast fermentation of the sugar
solution.
5. Distillation to produce 99.5% pure alcohol. 3.1 Pretreatment
of lignocellulosic materialsThe effect of pretreatment of
lignocellulosic materials has been recognized for a long time. The
purpose of the pretreatment is to remove lignin and hemicellulose,
reduce cellulose crystallinity, and increase the porosity of the
materials. Pretreatment must meet the following requirements: (1)
improve the formation of sugars or the ability to subsequently form
sugars by enzymatic hydrolysis; (2) avoid the degradation or loss
of carbohydrate; (3) avoid the formation of byproducts inhibitory
to the subsequent hydrolysis and fermentation processes; and (4) be
cost-effective. Physical, physico-chemical, chemical, and
biological processes have been used for pretreatment of
lignocellulosic materials
20
3.2. Physical pretreatment 3.2.1. Mechanical comminution
Waste materials can be comminuted by a combination of chipping,
grinding and milling to reduce cellulose crystallinity. The size of
the materials is usually 1030 mm after chipping and 0.22 mm after
milling or grinding. Vibratory ball milling has been found to be
more effective in breaking down the cellulose crystallinity of
spruce and aspen chips and improving the digestibility of the
biomass than ordinary ball milling. The power requirement of
mechanical comminution of agricultural materials depends on the
final particle size and the waste biomass characteristics.
3.2.2. PyrolysisPyrolysis has also been used for pretreatment of
lignocellulosic materials. When the materials are treated at
temperatures greater than 300 C, cellulose rapidly decomposes to
produce gaseous products and residual char. The decomposition is
much slower and less volatile products are formed at lower
temperatures. Mild acid hydrolysis (1 N H2SO4, 97 C, 2.5 h) of the
residues from pyrolysis pretreatment has resulted in 8085%
conversion of cellulose to reducing sugars with more than 50%
glucose .The process can be enhanced with the presence of oxygen
When zinc chloride or sodium carbonate is added as a catalyst, the
decomposition of pure cellulose can occur at a lower
temperature
3.3 Chemical pretreatment 3.3.1 OzonolysisOzone can be used to
degrade lignin and hemicellulose in many lignocellulosic materials
such as wheat straw, bagasse, green hay, peanut, pine, cotton
straw, and poplar sawdust. The degradation was essentially limited
to lignin and hemicellulose was slightly attacked, but cellulose
was hardly affected.The rate of enzymatic hydrolysis increased by a
factor of 5 following 60%21
removal of the lignin from wheat straw in ozone pretreatment.
Enzymatic hydrolysis yield increased from 0% to 57% as the
percentage of lignin decreased from 29% to 8% after ozonolysis
pretreatment of poplar sawdust. Ozonolysis pretreatment has the
following advantages: (1) it effectively removes lignin; (2) it
does not produce toxic residues for the downstream processes; and
(3) the reactions are carried out at room temperature and pressure.
However, a large amount of ozone is required, making the process
expensive.
3.3.2. Acid hydrolysisConcentrated acids such as H2SO4 and HCl
have been used to treat lignocellulosic materials. Although they
are powerful agents for cellulose hydrolysis, concentrated acids
are toxic, corrosive and hazardous and require reactors that are
resistant to corrosion. In addition, the concentrated acid must be
recovered after hydrolysis to make the process economically
feasible. Dilute acid hydrolysis has been successfully developed
for pretreatment of lignocellulosic materials. The dilute sulfuric
acid pretreatment can achieve high reaction rates and significantly
improve cellulose hydrolysis. At moderate temperature, direct
saccharification suffered from low yields because of sugar
decomposition. High temperature in dilute acid treatment is
favorable for cellulose hydrolysis. There are primarily two types
of dilute acid pretreatment processes: high temperature (T greater
than 160 C), continuous-flow process for low solids loading (510%
[weight of substrate/weight of reaction mixture]), and low
temperature (T less than 160 C), batch process for high solids
loading (1040%). Although dilute acid pretreatment can
significantly improve the cellulose hydrolysis, its cost is usually
higher than some physicochemical pretreatment processes. A
neutralization of pH is necessary for the downstream enzymatic
hydrolysis or fermentation processes.
3.3.3. Alkaline hydrolysisSome bases can also be used for
pretreatment of lignocellulosic materials and the effect of
alkaline pretreatment depends on the lignin content of the
materials. The mechanism of alkaline hydrolysis is believed to be
saponification of intermolecular ester bonds crosslinking xylan
hemicelluloses and other components, for example, lignin and other
hemicellulose. The porosity
22
of the lignocellulosic materials increases with the removal of
the crosslinks. Dilute NaOH treatment of lignocellulosic materials
caused swelling, leading to an increase in internal surface area, a
decrease in the degree of polymerization, a decrease in
crystallinity, separation of structural linkages between lignin and
carbohydrates, and disruption of the lignin structure ( Fan et al.,
1987). The digestibility of NaOH-treated hardwood increased from
14% to 55% with the decrease of lignin content from 2455% to 20%.
However, no effect of dilute NaOH pretreatment was observed for
softwoods with lignin content greater than 26%. Dilute NaOH
pretreatment was also effective for the hydrolysis of straws with
relatively low lignin content of 1018% used the combination of
irradiation and 2% NaOH for pretreatment of corn stalk, cassava
bark and peanut husk. The glucose yield of corn stalk was 20% in
untreated samples compared to 43% after treatment with electron
beam irradiation at the dose of 500 kGy and 2% NaOH, but the
glucose yields of cassava bark and peanut husk were only 3.5% and
2.5%, respectively. Ammonia was also used for the pretreatment to
remove lignin. Iyer et al. (1996) described an ammonia recycled
percolation process (temperature, 170 C; ammonia concentration,
2.520%; reaction time, 1 h) for the pretreatment of corn
cobs/stover mixture and switchgrass. The efficiency of
delignification was 6080% for corn cobs and 6585% for
switchgrass.
3.3.4. Oxidative delignificationLignin biodegradation could be
catalyzed by the peroxidase enzyme with the presence of H2O2. The
pretreatment of cane bagasse with hydrogen peroxide greatly
enhanced its susceptibility to enzymatic hydrolysis. About 50%
lignin and most hemicellulose were solubilized by 2% H2O2 at 30 C
within 8 h, and 95% efficiency of glucose production from cellulose
was achieved in the subsequent saccharification by cellulase at 45
C for 24 h. used wet oxidation and alkaline hydrolysis of wheat
straw (20 g straw/l, 170 C, 510 min), and achieved 85% conversion
yield of cellulose to glucose.
23
3.3.5. Organosolv processIn the organosolv process, an organic
or aqueous organic solvent mixture with inorganic acid catalysts
(HCl or H2SO4) is used to break the internal lignin and
hemicellulose bonds. The organic solvents used in the process
include methanol, ethanol, acetone, ethylene glycol, triethylene
glycol and tetrahydrofurfuryl alcohol. Organic acids such as
oxalic, acetylsalicylic and salicylic acid can also be used as
catalysts in the organosolv process. At high temperatures (above
185 C), the addition of catalyst was unnecessary for satisfactory
delignification. Usually, a high yield of xylose can be obtained
with the addition of acid. Solvents used in the process need to be
drained from the reactor, evaporated, condensed and recycled to
reduce the cost. Removal of solvents from the system is necessary
because the solvents may be inhibitory to the growth of organisms,
enzymatic hydrolysis, and fermentation.
3.4. Biological pretreatmentIn biological pretreatment
processes, microorganisms such as brown-, white- and soft-rot fungi
are used to degrade lignin and hemicellulose in waste materials.
Brown rots mainly attack cellulose, while white and soft rots
attack both cellulose and lignin. White-rot fungi are the most
effective basidiomycetes for biological pretreatment of
lignocellulosic materials. Hatakka (1983) studied the pretreatment
of wheat straw by 19 white-rot fungi and found that 35% of the
straw was converted to reducing sugars by Pleurotus ostreatus in
five weeks. Similar conversion was obtained in the pretreatment by
Phanerochaete sordida 37 and Pycnoporus cinnabarinus 115 in four
weeks. In order to prevent the loss of cellulose, a cellulase-less
mutant of Sporotrichum pulverulentum was developed for the
degradation of lignin in wood chips also reported the
delignification of Bermuda grass by white-rot fungi. The
biodegradation of Bermuda grass stems was improved by 2932% using
Ceriporiopsis subvermispora and 6377% using Cyathus stercoreus
after 6 weeks. The white-rot fungus P. chrysosporium produces
lignin-degrading enzymes, lignin peroxidases and
manganese-dependent peroxidases, during secondary metabolism in
response to carbon or nitrogen limitation (Boominathan and Reddy,
1992). Both enzymes have been found in the extracellular filtrates
of many white-rot fungi for the degradation of wood cell walls.
Other24
enzymes including polyphenol oxidases, laccases, H2O2 producing
enzymes and quinonereducing enzymes can also degrade lignin. The
advantages of biological pretreatment include low energy
requirement and mild environmental conditions. However, the rate of
hydrolysis in most biological pretreatment processes is very
low
3.5 Hydrolysis processesThe cellulose molecules are composed of
long chains of glucose molecules. In the hydrolysis process, these
chains are broken down to "free" the sugar, before it is fermented
for alcohol production. There are two major hydrolysis processes: a
chemical reaction using acids, or an enzymatic reaction.
3.5.1 Acid hydrolysisAcid hydrolysis has been investigated as a
possible process for treating lignocellulosic materials such as
wood chips, rice straw, sugar beet pulp and wheat straw. The
mineral acids act simply and rapidly as reaction catalyzers of
polysacharide fractions. Sugarcane bagasse can be hydrolyzed using
dilute acid to obtain a mixture of sugars with xylose as the major
component. However, in the hydrolyzate some by-products generated
in the hydrolysis, such as acetic acid, furfural, phenolic
compounds, or lignin degradation products, can be present. These
are potential inhibitors of a microbiological utilization of this
hydrolyzate. Processes such as two-stage acid hydrolysis can be
employed to produce xylose and glucose. Treatment with dilute
sulphuric acid at moderate temperatures (the first stage of acid
hydrolysis) has proven to be an efficient means of producing xylose
from hemicellulose. In the second stage more drastic reaction
conditions are employed and glucose can be produced from cellulose
hydrolysis. In general, acid treatment is effective in solubilizing
the hemicellulosic component of biomass. Proper combinations of pH,
temperature, and reaction time can result in high yields of sugars,
primarily xylose from hemicelluloses. Sulphuric acid is a catalyst
for this reaction and, in this work, was used to study the
hydrolysis of sugarcane bagasse hemicellulose. The effects of
temperature, acid concentration and reaction time were25
studied, and the effectiveness of the hydrolysis was evaluated
in terms of hemicellulose solubilization.
3.6 Sugar Fermentation in Yeast
Yeast are able to metabolize some foods, but not others. In
order for an organism to make use of a potential source of food, it
must be capable of transporting the food into its cells. It must
also have the proper enzymes capable of breaking the foods chemical
bonds in a useful way. Sugars are vital to all living organisms.
Yeast are capable of using some, but not all sugars as a food
source. Yeast can metabolize sugar in two ways, aerobically, with
the aid of oxygen, or anaerobically, without oxygen.
In this lab, you will try to determine whether yeast are capable
of metabolizing a variety of sugars. Although aerobic fermentation
of sugar is much more efficient, in this experiment we will have
yeast ferment sugars anaerobically. When the yeast respire
aerobically, oxygen gas is consumed at the same rate that CO2 is
producedthere would be no change in the gas pressure in the test
tube. When yeast ferments the sugars anaerobically, however, CO2
production will cause a change in the pressure of a closed test
tube, since no oxygen is being consumed. We can use this pressure
change to monitor the respiration rate and metabolic activity of
the organism. A gas pressure sensor will be used to monitor the
fermentation of sugar.
The fermentation of glucose can be described by the following
equation: C6Hl2O6 2 CH3CH2OH +2 CO2 + energy
Note that alcohol is a byproduct of this fermentation.
1. Yeast cannot utilize all of the sugars equally well. While
glucose, sucrose, and fructose all can be metabolized by yeast,
lactose is not utilized at all.
26
2. Yeast may not have the proper enzymes to either transport
lactose across its cell membrane, or it may not have the enzyme
needed to convert it from a disaccharide to a monosaccharide.
3. The yeast need to be incubated so that the oxygen in the test
tube will be completely consumed. If the yeast respire aerobically,
no pressure change occurs, because much oxygen is consumed as CO2
is produced. It also takes a few minutes for the yeast to transport
the sugar into the cell, to respire at a constant rate, and to
reach the proper temperature.
4. Some yeast live on other organisms. If they are warm blooded,
they may be near the optimal temperature for yeast respiration,
37C. Many yeast live in soils. The temperature of soils may easily
be measured at different times of the year.
27
Chapter 4
MATERIALS & EQUIPMENT USED
28
4.1 MATERIALS USED 4.1.1 Chemicals Required i. ii. iii.iv.
Dilute Sulfuric acid Concentrated NaOH Phenol Sodium
hydroxide
= 0.2 M, 0.3 M, 0.5 M = dropwise = = 2 gm 10 gm
4.2 EQUIPMENTS REQUIRED 4.2.1 Vertical autoclave This equipment
is primarily used for sterilization purpose. It is an enclosed
space where steam bath is given to any equipment placed inside it.
Water filled in it is heated by electric coils present at bottom.
It has a vent at top, from where the steam can be released to
maintain the required pressure. For our case, sterilization is
required after maintaining the pH and also for each filtration.
Pressure around 2.02 kg/cm2 is used. Once the pressure reaches 2.02
kg/cm2, it is maintained for half an hour. The equipments are
allowed to cool down before removing from the autoclave.
Figure 1 Vertical autoclave
29
4.2.2 Laminar flow chamber A laminar flow cabinet or laminar
flow closet or tissue culture hood is a carefully enclosed bench
designed to prevent contamination of semiconductor wafers,
biological samples, or any particle sensitive device. Air is drawn
through a HEPA filter and blown in a very smooth, laminar flow
towards the user. The cabinet is usually made of stainless steel
with no gaps or joints where spores might collect. Such hoods exist
in both horizontal and vertical configurations, and there are many
different types of cabinets with a variety of airflow patterns and
acceptable uses
4.2.3 Vaccum Filtration Vacuum filtration is a technique for
separating a solid product from a solvent or liquid reaction
mixture. The mixture of solid and liquid is poured through a filter
paper in a Buchner funnel. The solid is trapped by the filter and
the liquid is drawn through the funnel into the flask below, by a
vacuum.
4.2.4 UV-Spectrophotometer The UV-Visible spectrophotometer uses
two light sources, a deuterium (D2) lamp for ultraviolet light and
a tungsten (W) lamp for visible light. After bouncing off a mirror
(mirror 1), the light beam passes through a slit and hits a
diffraction grating. The grating can be rotated allowing for a
specific wavelength to be selected. At any specific orientation of
the grating, only monochromatic (single wavelength) successfully
passes through a slit. A filter is used to remove30
unwanted higher orders of diffraction. The light beam hits a
second mirror before it gets split by a half mirror (half of the
light is reflected, the other half passes through). One of the
beams is allowed to pass through a reference cuvette (which
contains the solvent only), the other passes through the sample
cuvette. The intensities of the light beams are then measured at
the end. 4.2.5 Shaking incubator Incubator Shaker is a large
capacity shaking incubator which may be stacked up to 3 high,
offering a large capacity in a minimum of floor space. The
ingenious design of the Infors shakers features a front-loading
pullout platform, stainless steel interior panels, panoramic front
window and inspection light. The patented drive system provides
uniform motion and quiet operation without vibration. 4.2.6 pH-
meter A pH meter is an electronic instrument used to measure the pH
(acidity or alkalinity) of a liquid. A typical pH meter consists of
a special measuring probe (a glass electrode) connected to an
electronic meter that measures and displays the pH reading
31
Chapter 5
PROCEDURE OF EXPERIMENT
32
5.1 Pretreatment of bagasseAbout 1 kg of post harvest sugarcane
bagasse is taken and dried to remove all the moisture present in
it. This dried sugarcane bagasse undergoes size reduction by the
help of a grinder. Even the powdered form is used for
hydrolysis.
5.2 HydrolysisThe cellulose molecules are composed of long
chains are broken down to free the sugar, before it is fermented
for alcohol production. Though hydrolysis is of many types, dilute
acid hydrolysis is an easy and productive process. Also the amount
of alcohol produced in case of acid hydrolysis is more than that of
alkaline hydrolysis. Concentrated acid hydrolysis is not used as it
is a hazardous and corrosive process and also acid has to be
separated out after hydrolysis for the experiment has to be
feasible.
5.2.1 Steps involved in dilute acid hydrolysis are1. 4 nos. of
250 ml of conical flasks were taken and to each of them 5 gm of
grinded sugarcane bagasse is added carefully. 2. Another flask of
500 ml size is taken and to it 5 gm of grinded sugarcane bagasse is
added carefully. 3. 100 ml of dilute sulfuric acid of concentration
0.2 M is added to the 500 ml flask. 4. 100 ml of dilute sulfuric
acid of concentration 0.3 M is added to two of them 250 ml flasks.
5. 100 ml of dilute sulfuric acid of concentration 0.5 M is added
to the remaining two 250 ml flasks. 6. All this samples are left to
be soaked to dilute sulfuric acid for 24 hrs.
7. The bottles were then capped with the help of cotton
plugs.
33
5.3 pH adjustmentBefore addition of any micro-organism to the
above prepared samples, pH of these samples has to be adjusted.
Otherwise the micro-organism will die in hyper acidic or basic
state. A pH of around 5-5.5 is maintained.
5.3.1 Steps involved in pH adjustment are1. The 500 ml flask
containing 0.2 M dilute sulfuric acid hydrolyzed bagasse is taken
and its pH is checked with the help of a pH meter. 2. As samples
are acid hydrolyzed, a highly basic solution is added to bring the
pH in the range of 5-5.5. 3. For this purpose, a highly
concentrated NaOH solution is prepared by mixing weater with Na
pellets. 4. This NaOH solution is added drop wise to the 0.2 M 500
ml flask with constant stirring until the pH reaches to a range of
5-5.5 5. If suppose the pH goes beyond 5-5.5, concentrated HCl acid
is added drop wise to maintain the pH in the range. 6. The above
steps are repeated for the 0.3 M and 0.5 M dilute sulfuric acid
hydrolyzed bagasse. After maintaining the pH, the samples are kept
in a Vertical autoclave for hr at 1200C (around 2.02 kg/cm2
pressure) and allowed to cool.
5.4 Fermentation 5.4.1 Media preparationFor preparing 100 ml
media, we add Sugar (Dextrose) Yeast extract Urea Make up water =
10 gm = 0.2 gm = 1 gm = 100 ml
34
5.4.2 Steps involved in fermentation are1. To the above 100 ml
media, 0.5 gm of yeast ( Saccharomyces cerevisiae) is added in a
250 ml conical flask. 2. This conical flask is then placed in a
shaking incubator for 24 hrs. 3. 10 ml of this medium is then added
to each of the 5 autoclaved samples aseptically in a Laminar flow
chamber. 4. These flasks are properly covered with cotton plug. 5.
These flasks are then placed in the shaking incubator at a
temperature of 35oC and 120 rpm. 6. After 24 hrs, the flasks are
covered with aluminium foils over the cotton plug.
35
Chapter 6
RESULTS
36
6.1 Standard plot for ethanol
16 ml of absolute ethanol was mixed with 24 ml of water and an
absorbance of 0.897 nm was found in the UV spectrophotometer. This
was assumed to be 100 % ethanol and the standard plot was drawn.
SL.NO. Amount of ethanol (in ml) 1 2 3 4 5 6 7 8 9 10 11 0 0.3 0.6
0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 Amount of water (in ml) 3.0 2.7 2.4
2.1 1.8 1.5 1.2 0.9 0.6 0.3 0 0 10 20 30 40 50 60 70 80 90 100 0
0.185 0.223 0.291 0.376 0.419 0.611 0.665 0.734 0.8 0.897 Conc. Of
ethanol Absorbance
Table 6.1
37
The 100 percent of this ethanol is actually the 40 percent
concentration of absolute alcohol. Therefore the actual standard
plate is given in the next table.
SL.NO.
Amount of ethanol ( in ml)
Amount of water ( in ml) 3.0 2.7 2.4 2.1 1.8 1.5 1.2 0.9 0.6 0.3
0
Conc. Of ethanol
Absorbance
1 2 3 4 5 6 7 8 9 10 11
0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0
0 40 180 120 160 200 240 280 320 360 400
0 0.185 0.223 0.291 0.376 0.419 0.611 0.665 0.734 0.8 0.897
Table 6.2
38
1 0.9 0.8 0.7 Absorbance 0.6 0.5 0.4 0.3 0.2 0.1 0 0 100 200
Ethanol conc. 300 400 500
Figure 6.1
39
6.2 ANALYSIS OF ETHANOL FOR DIFFERENT DAYS
Day 1 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.3 Absorbance (210 nm) 0.62 0.54 0.581 0.523 0.568
0.63 0.62 0.61 0.6 0.59 0.58 0.57 0.56 0.55 0.54 0 0.2 0.4
0.6
Figure 6.2
40
Day 2 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.4 Absorbance (210 nm) 0.667 0.605 0.589 0.558 0.529
0.68 0.66 0.64 0.62 0.6 0.58 0.56 0.54 0.52 0.5 0 0.2 0.4
0.6
Figure 6.3
41
Day 3 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.5 Absorbance (210 nm) 0.678 0.667 0.624 0.637 0.563
0.69 0.68 0.67 0.66 0.65 0.64 0.63 0.62 0.61 0.6 0.59 0 0.2 0.4
0.6
Figure 6.4
42
Day 7 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.6 Absorbance (210 nm) 0.712 0.672 0.671 0.667 0.598
0.72 0.71 0.7 0.69 0.68 0.67 0.66 0.65 0.64 0.63 0.62 0 0.2 0.4
0.6
Figure 6.5
43
Day 8 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.7 Absorbance (210 nm) 0.723 0.678 0.691 0.695 0.601
0.73 0.72 0.71 0.7 0.69 0.68 0.67 0.66 0.65 0.64 0 0.2 0.4
0.6
Figure 6.6
44
Day 9 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.8 Absorbance (210 nm) 0.735 0.701 0.742 0.718 0.655
0.74
0.73
0.72
0.71
0.7
0.69
0.68 0 0.2 0.4 0.6
Figure 6.7
45
Day 10 Sl. No. 1 2 3 4 5 Sample 0.2 0.3 (I) 0.3(II) 0.5(I)
0.5(II)
Table 6.9 Absorbance (210 nm) 0.753 0.721 0.742 0.736 0.698
0.755 0.75 0.745 0.74 0.735 0.73 0.725 0.72 0.715 0 0.2 0.4
0.6
Figure 6.8
46
6.3 COMPARISON OF NUMBER OF DAYS For 0.2 M acid
concentration
ETHANOL
CONCENTRATION
WITH
INCREASING
Table 6.10 SL. NO. 1 2 3 4 5 6 7 8 9 10 NO. OF DAYS 1 2 3 4 5 6
7 8 9 10 ETHANOL CONC. 276.47 297.43 302.34
317.50 322.40 327.76 335.78
The graph of the above table is as follows360 340 320 Ethanol
conc. 300 280 260 240 220 200 0 2 4 6 no. of days 8 10 12
Figure 6.9
47
For 0.3 M acid concentration SL. NO. 1 2 3 4 5 6 7 8 9 10 NO. OF
DAYS 1 2 3 4 5 6 7 8 9 10 Table 6.11 ETHANOL CONC. 249.94 275.39
287.85
299.44 305.24 321.74 326.19
The graph of the above table is as follows340 320 300 Ethanol
conc. 280 260 240 220 200 0 2 4 6 No. of days 8 10 12
Figure 6.10
48
For 0.5 M acid concentration SL. NO. 1 2 3 4 5 6 7 8 9 10 NO. OF
DAYS 1 2 3 4 5 6 7 8 9 10 Table 6.12 The graph of the above table
is as follows340 320 300 Ethanol conc. 280 260 240 220 200 0 2 4 6
No. of days 8 10 12
ETHANOL CONC. ( ml/lt) 243.25 251.36 267.55
288.74 295.96 306.13 328.73
Figure 6.11
49
Chapter 7
DISCUSSION
50
1. The ethanol concentration in ml/lt of acid hydrolyzed bagasse
increases with the increasing number of days. 2. This shows that
the sugar is being fermented by the help of micro organism yeast
for the production of ethanol. 3. The maximum concentration of
ethanol is 328.73 ml/lt of acid hydrolyzed bagasse which was found
on the 10th day of fermentation. 4. In absorbance vs molarity curve
, after each progressive data the curve tends to come in a straight
line. 5. For 0.3 M and 0.5 M we have taken two identical samples
for each for better accuracy. 6. For drawing graphs, in case of 0.3
M, 0.5 M samples average is taken. 7. Still some deflection in the
graphs can be considered due to precision error, long duration of
experiment, and human errors.
51
Chapter 8
REFERENCES
52
1. Biosource technology, Volume 83 Issue 1, May 2002. 2.
Biosource Technology, Volume 77, Issue 2, April 2001. 3. Cellulosic
Ehanol- Wikipedia, The free encyclopedia. 4. Ethanol From
Cellulose: A General Review Trends in new crops and new uses. 2002.
J. Janick and A. Whipkey (eds.). ASHS Press, Alexandria, VA. 5.
Ethanol production via enzymatic hydrolysis of sugar edition 1996
Elba P.S. Bon 6.
www.osti.gov/bridge/servlets/purl/755492CufN/webviewable/755492 7.
www.ethtec.com.au/downloads/Latest_News/ETHANOL_FROM_BAG
ASSE_MEETINGS 8. Renewable and Sustainable Energy Reviews, Volume
13, Issues 6-7, August-September 2009, Pages 1418-1427 9.
www.cellulosicroundtable.com/greenfieldethanol.htm 10.
www.bioresourcesjournal.com/index.php/BioRes11.
sciencestage.com/d/29329/lime-pretreatment-of-sugarcane-bagasse-
for-bioethanol-production12.
www.academicjournals.org/ajb/PDF/pdf2008/18Jul/Damisa%20et%20
al.13.
aiche.confex.com/aiche/2006/preliminaryprogram/abstract_58322.ht
m14.
www.rurdev.usda.gov/rbs/pub/sep06/ethanol.htm53
54
55
Dr. Arvind Kumar
56