laboratory Fermentation of ethyl alcohol from molasses this shows how fermentation can be carried out in laboratory a simple flow sheet and precautions to be taken in lab mentioned in {annexure 1} and about how enzymes carry out catalysis about yeast and industrial fermenntation
ANNEXURE-I 1. Safety Precaution used in Laboratory Level:- i. No running and jumping in laboratory areas shall be permitted. ii. Lab coats and safety glasses are required in laboratories employing chemicals or bio hazards. iii. Foot wear and clothing are to be wear which will not create sparks. iv. Using nylon clothes is avoided as it can produce static electricity. v. Wash your hands frequently throughout the day and before leaving the lab. vi. Do not smoke and carry the matches. vii. Keep all aisles and walk ways into the lab clear to provide a safe walking surface. viii. Never pipette out by mouth. Always use a pipette bulb. ix. Wear apron while doing the experiment and also shoes. x. Be alert and don’t be in dream while handling chemicals and electrical equipment’s. xi. Do not stopper on to glass tubing’s. 1
Transcript
ANNEXURE-I
1. Safety Precaution used in Laboratory Level:-
i. No running and jumping in laboratory areas shall be permitted.
ii. Lab coats and safety glasses are required in laboratories employing
chemicals or bio hazards.
iii. Foot wear and clothing are to be wear which will not create sparks.
iv. Using nylon clothes is avoided as it can produce static electricity.
v. Wash your hands frequently throughout the day and before leaving the
lab.
vi. Do not smoke and carry the matches.
vii. Keep all aisles and walk ways into the lab clear to provide a safe walking
surface.
viii. Never pipette out by mouth. Always use a pipette bulb.
ix. Wear apron while doing the experiment and also shoes.
x. Be alert and don’t be in dream while handling chemicals and electrical
equipment’s.
xi. Do not stopper on to glass tubing’s.
xii. Report all incidents/accidents to your teacher immediately.
xiii. Never throw sodium metal in sink.
xiv. Notify your instructor about fire accidents immediately to take steps for
firefighting.
xv. Chemical Burn:
General chemicals: Immediately warm off plenty of water.
xvi. Acids: Wash with water and then with dilute Na2Co3 solutions.
xvii. Bases: Wash with water.
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2. Safety Precautions used in Distillery Plant:-
i. Don't distill in a closed room. Try and keep some through-draught (e.g.
both a window and door open)
ii. If your still leaks (liquid or steam) - fix it instead of using it
iii. Collect the alcohol securely – don’t put yourself in a position where it’s
easy to knock over the collection vessel etc., or bump the tube out of it.
This means having enough space to work in, well lit, tidy.
iv. Keep a fire extinguisher with you (and on your side of whatever is going to
catch fire)
v. If using electrical heating, have an RCD on the line (residual current
device - a fancy circuit breaker)
vi. Check you’re still with water-only the first time you use it, to make sure
your condenser is up to the job. You don’t want vapor coming out of the
collection tube.
vii. Be sober - it’s not a time to be making drunken mistakes.
viii. Pay attention to the still - check it regularly (cooling water still flowing, no
leaks, collecting nicely, all temperatures OK).
ix. Do the math - don't boil the still dry.
x. Make sure the outlet tube is free flowing - not crimped or blocked in any
way.
xi. Make sure the still design is such that you can't pressurize the still - it
should always be able to vent somehow to atmosphere. There shouldn't be
valves such that you can fully close the column off.
xii. Don't smoke - you don't want ignition sources around a liquid as
flammable as gasoline.
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ANNEXURE-II
3. Introduction to Fermentation:-
Fermentation process utilizes micro-biology in production chemical compounds. These process yield simple structural chemicals, e.g. - ethanol, butanol or acetone etc. Fermentation processes are also used for production of complex organics chemicals such as medicinal, antibiotics and for chemicals of more complex structure, such as citric and lactic acids derived from low-cost carbohydrate sources.
The action of a specific micro-organism on a substrate to produce the desired chemical compound is termed Fermentation. The majority of processes required oxygen and are called classified as “Aerobic”. The few processes carried out in the absence of air are classified as “anaerobic”.
Fermentation under controlled conditions involves chemical conversions some of the more important processes are:
Oxidation: e.g. Alcohol to acetic acid, Sucrose to citric acid, and dextrose to
gluconic acid,
Reduction: e.g. Aldehydes to Alcohols, (acetyl dehyde to Ethyl Alcohols), and
Sulphur to Hydrogen Sulfide.
Hydrolysis: e.g. Starch to Glucose and Sucrose to Glucose and Fructose and on to
alcohol,
Esterification: e.g. Hexose phosphate from Hexose and Phosphoric acid.
Actually certain chemicals conversions can be carried out more efficiently by
fermentation then by chemical synthesis.
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4. Characteristics of Fermentation Process:
The five basic prerequisites of a good fermentation process are:-
i. A micro-organism that forms desired end product. This organism must be
readily propagated and be capable of maintaining biological uniformity,
thereby giving predictable yields.
ii. Economical raw materials for the substrate e.g. starch or on of several
sugars.
iii. Acceptable yields.
iv. Rapid Fermentation.
v. A product that is rapidly recovered and purified.
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5. Introduction to Alcohols:-
Ethyl alcohol is one of the most important raw materials which is quite
frequently used. It is most important member of the alcohol series and is simply
known as “Alcohol”. It is also known as “Grain Alcohol” because it can be
prepared from starchy grains. It has become important by virtue of its
economically useful properties as a solvent and for synthesis of other
chemicals. Alcohol is sold as a tax paid alcohol or much more widely as non-
taxed denatured alcohol.
In industries nomenclature alcohol means ethyl alcohol or ethanol
(C2H5OH).
Structure of Ethanol
Ethanol is an alternative energy source. When burned, ethanol produces a pale
blue flame with no residue and considerable energy, making it an ideal fuel. It
can be used as a fuel when blended with gasoline or in its original state. There
are three primary ways that ethanol can be used as a transportation fuel:
i. As a blend of 10 percent ethanol with 90 percent unleaded gasoline called “E-10 Unleaded”;
ii. As a component of reformulated gasoline, both directly and/or as ethyl tertiary butyl ether (ETBE); or
iii. As a primary fuel with 85 parts of ethanol blended with 15 parts of unleaded gasoline called “E-85.”
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6. Methods of Preparation of Ethyl Alcohol:-
On industrial scale, alcohols are prepared by the following methods:
A. Hydration of alkenes:
Alkenes are converted into alcohols by two methods:
i. By direct addition of water at low temperature and high pressure in the
presence of mineral acids as catalyst.
ii. By indirect method in which alkenes are passed through concentrated
H2SO4 to form alkyl hydrogen sulphates. These alkyl hydrogens
sulphates are hydrolysed by passing steam which gives alcohols.
B. Oxo Process:
Alkenes react with carbon monoxide and hydrogen in the presence of
cobalt carbonyl [Co(CO)4]2 as catalyst at high temperature and pressure
to give aldehydes. The catalytic hydrogenation of aldehydes gives
primary alcohols.
H2/Ni
H2C=CH2+CO+H2 CH3CH2CHO CH3CH2CH2OH
Propanal Propan-1-ol
C. Fermentation of Carbohydrates.
Ethanol is manufactured by fermentation of starch or sugar. Fermentation is
a process in which complex organic compounds are broken down into
simpler molecules by the action of biological catalysts known as enzymes.
Enzymes are complex organic compounds which acts as catalysts in reaction
taking place in living organisms. These are also called Bio-catalysts
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[Co (Co)4]2
High temp. & Pressure
ANNEXURE-III
7. Fermentation of Carbohydrates:-
7.1 Properties of Enzymes:
The important characteristics of enzymes are:
i. High efficiency: Enzymes increase the speed of reaction up to 10
million times as compared to the uncatalysed reactions.
ii. Extremely small quantities: Extremely small quantities of enzymes –as
small as millionth of a mole-can increase the rate of reaction by factors
of 103 to 106
iii. Specificity: The enzymes are highly specific in nature. Almost every
biochemical reaction is controlled by its own specific enzymes. For
example, Maltase catalyses the hydrolysis of maltase. No other enzyme
can catalyse its hydrolysis.
iv. Optimum temperature and pH: The enzymes are active at moderate
temperature (about 37oC) and pH (around 7).
v. Control of activity of enzymes: The actions of enzymes are controlled
by various mechanisms and are inhibited by various organic and
inorganic molecules.
vi. The activity of most enzymes is closely regulated.
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7.2 Enzymes catalyzed Reactions:
Bio chemists are trying to explain the exact molecular basis of enzyme
catalysis. The various steps involved in the enzyme catalyzed reaction are
given below:
i. Binding of the enzymes (E) to substrate (S) to form a complex.
E+S ES
ES is called the enzyme- substrate complex.
ii. Product formation in the Complex.
ES EP
Where EP is a complex of enzyme and product.
iii. Release of product from the enzyme – Product complex.
EP E+P
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The catalystic property of enzymes is present at certain specific regions on their
surfaces. These are called active sites or catalystic sites. The active sites have
characteristic shape and fit suitably shaped specific substrate molecules. Specific
binding accounts for the high specificity of these enzyme reactions. The specificity
of fitting together of the substrate structure and the enzyme structure may be
compared as a Key fitting into a lock. The shape of the active site is of given
enzymes is such that only a specific substrate can fit into it, on the same way as
key can open a particular lock.
Enzyme Substrate Binding(Lock and key mechanism)
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7.3 Introduction to Yeast:-
The word "yeast" comes from Old English gist, gyst, and from the Indo-
European root yes-, meaning "boil", "foam", or "bubble". Yeasts are eukaryotic
microorganisms classified in the kingdom Fungi, with 1,500 species currently
described (estimated to be 1% of all fungal species). Yeasts are unicellular,
although some species with yeast forms may become multicellular. Yeast size
can vary greatly depending on the species, typically measuring 3–4 µm in
diameter.
Structure of Yeast
Raising bubbles from Yeast
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Action of Yeast at the time of Fermentation
The yeast species Saccharomyces cerevisiae converts carbohydrates to carbon
dioxide and alcohols. This is because:
a. They grow vigorously.
b. They have high tolerance for alcohols.
c. They have a high capacity for producing a large yield of alcohol.
d. For yeast nutrients are needed such as small amount of phosphate and
nitrogenous compounds as well as favorable pH and temperature.
7.4 Pertinent properties of Ethyl Alcohol (Ethanol):-
Molecular weight 46.07Density 0.791 @ 20oCMelting Point -112oCBoiling Point 78.3oCFlash Point 21oCIgnition Temperature 372oCExplosive limits Lower = 3.5% by Volume
7.6 Ethyl Alcohol from Sugar solution (Molasses):-
Molasses is a non-crystalline of sugar obtained as mother liquor after
crystallization of sugar from sugar solution. This contains about 50% sugar. It
is diluted to about 10% solution. The process can be explained in the following
two stages:
a) Cultivation of Yeast in the molasses.
b) Recovery of Ethyl alcohol from cultivated solution.
I stage:As shown in the diagram diluted solution is heated up to above room
temperature (40-50oC) and then yeast is added proportionality and kept for
cultivation for about 2-3 days. Yeast supplies the enzymes invertase and
zymase. The enzyme invertase hydrolysis sucrose to glucose and fructose. The
enzyme zymase converts glucose to ethanol and carbon dioxide.
C12H22O11 + H2O C6H12O6 + C6H12O6
C6H12O6 2C2H5OH + 2CO2 H= -31.2K Cal
The formation of final products i.e., ethanol and carbon dioxide can be
observed by the bubbler (expanded bubbler) which is tied to the cultivation can
be observed in the diagram.
The fermented liquid which contains about 8-10% ethanol is called “Wash”.
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Invertase
Glucose FructoseSucrose
ZymaseGlucose Ethanol
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II Stage:
As observed in the diagram the “mash” is collected and fractionally distilled to
recover rectified spirit containing 95.6% alcohol. The final rectified alcohol is
stored in cans. Further dehydration with quick lime and distilling with sodium
or calcium gives 99.8% ethanol called absolute alcohol.
Laboratory Fermenter
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ANNEXURE-IV
8. Industrial alcohol production by fermentation:
8 .1 Flow Sheet:
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8.2 Chemical Reaction:
a. Main Reaction:
C12H22O11 +H2O 2C6H12O6
C6H12O6 2C2H5OH + 2CO2; ∆H= -31.2 Kcal
b. Side Reaction:
2C6H12O6 + H2O ROH + R’CHO
8.3 Quantitative requirements:
a) Basis: 1 Ton of 100 % alcohol (1.26 kilometers) and 90% yield from total
sugar.
Molasses (50-55% total sugar) 5.6 tons.Sulfuric acid (60o Be) 27 kgAmmonium sulfate 2.5 kgCoal 0.87 - 1.5 tonsProcess water 12 tonsCooling Water 50 tonsElectricity 35 KWHBy-products: Co2 0.76 tons
Fusel oil (higher mol. Wt. alcohols)
Residual cattle feed or fertilizer 0.20 – 0.60 ton
b) Plant capacity: 10-100 tons/day of ethyl alcohol.
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Invertase
Zymase
Higher mol. Wt. alcohols
8.4 Process Description:
Molasses is diluted to a 10-15% sugar concentration and adjusted to a pH of 4-5 to support yeast growth which furnishes invertase zymase catalytic enzymes. Nutrients such as ammonium and magnesium sulfate or phosphate are added when lacking in molasses. This diluted mixture, called mash, is run into large wooden or steel fermentation tanks
Yeast solution, grown by inoculating sterile mash, is added and fermentation ensues with evolution of heat which is removed via cooling coils. The temperature is kept at 20-30oC over a30-70 hour period, rising near the end to 35oC carbon dioxide may be utilized as a by-product by water scrubbing and compressing; otherwise it is vented after scrubbing.
Separation of the 8-10% of alcohol in the fermented liquor called beer is accomplished by a series of distillations. In the beer still, alcohol (50-60%conc.) and undesirable volatiles such as aldehydes are taken off the top and fed to the aldehyde still. Alcohol is pulled off as a side-stream spilt to the rectifying column. In this final column, the azeotropic alcohol-water mixture of 95% ethanol is taken off as a top side-stream, condensed and run to storage where it is spilt into three parts:
(1) Direct sale as potable, government controlled alcohol.
(2) Denatured by small additions of mildly toxic ingredients and sold for
industrial uses.
(3) Made anhydrous by ternary azeotropic distillation using benzene or
extractive distillation using ethylene glycol.
When fusel oil recovery is practiced, side-streams are drawn off near the bottom of the aldehyde and rectifying columns and are separated by decantation. These higher molecular weight alcohols are sold directly for solvents or are fractionated to give predominately amyl alcohol.
The bottoms from the beer still, known as slops, are either discharged as waste or concentrated by evaporation to cattle feed depending on fuel and by-product sales economics.
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9. Influence of Reaction of Parameters:-
The following parameters influence the production of ethyl alcohol from
molasses by Fermentation.
The yield of ethyl alcohol depends on effective cultivation of yeast in the
molasses.
9.1 Optimization of pH:
As shown in the figure.1 the ethanol concentration gradually increase in pH
and reaches a maximum percentage of ethanol production when pH is equal to
4 and later it starts declining due to the lesser activity of yeast.
Optimum pH is 4.2 to 4.5
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9.2 Effect of fermentation temperature:
The sample maintained at an optimum pH (4pH), the ethanol production
increases with the increase in the temperature and reaches maximum value
at 35oC as shown in below figure.
Further the increasing temperature reduces the percentage of ethanol
production and is mainly due to the denature of the yeast cells.
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9.3 Effect of Molasses Concentration:
As shown in fig. 3 that the production of ethanol increases in sugar
molasses concentration and reaches maximum. Ethanol production of
sugar concentration of 300 gm/lt and further increasing sugar molasses
concentration inhibit the ethanol productivity.
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9.4 Effect of Yeast concentration:
When pH and temperature are maintained at 4 & 35oC from figure 4. It is
observed that as the concentration of yeast increases, the yield of ethanol
increases up to 2 gm. and then it starts to decrease.
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ANNEXURE-V
10. Properties of Ethyl Alcohol:
10.1 Physical Properties:
The important physical properties of alcohols are:
i. Physical state:
The lower members are colorless liquids having a characteristic smell and
burning taste. The higher members (having more than 12 carbon atoms) are
colorless, odorless, wax-like solids.
ii. Associated nature:
Alcohols exit as associated molecules having intermolecular hydrogen
bonds as shown below,
R R
…….O H…….O H……O H…..
RThis is due to the fact that there is large difference in electronegativity of oxygen and hydrogen atoms. As a result the O H bonds is strongly polar and forms hydrogen bonds.
iii. Boiling Point:The lower member have low boiling point but with the increase in molecular weight, the boiling point keep on increasing gradually. For isomeric alcohols having the same number of carbon atoms, the boiling points are in the order:
This is due to the fact that with branching, the surface area decreases and therefore , the boiling point decreases.
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Hydrogen Bonds
It may be noted that alcohols have generally higher boiling points as compared to other organic compound of similar molecular masses such as hydrocarbons, ethers and haloalkanes. For example, the boiling point of ethyl alcohol (mol. Mass=46) dimethyl ether (mol. Mass=46) and propane (mol. mass=44) are:
Ethyl alcohol Dimethyl ether Propane 351 K 309 K 231K
This is due to the presence of hydrogen bonds in alcohols and their absence in ethers and hydrocarbons. Because of hydrogen bonds in alcohols, these exists as associated molecules rather than discrete molecules. Consequently, a large amount of energy is required to break these bonds and therefore, their boiling points are high.
iv. Solubility:The lower members of alcohol are highly soluble in water but the solubility decreases with increases in molecular weight. The solubility of lower alcohols in water is due to the formation of hydrogen bonds between alcohols and water molecules.
R R
…….O H…….O H……O H…..O H……
H H
However, as the size of alcohol molecules increases, the alkyl group becomes larger and prevents the formation of hydrogen bonds with water molecules and hence the solubility goes a decreasing with increases in length of carbon chain (or molecular mass of alcohol).
Amongst isomeric alcohols, the solubility increases with branching. v. Density:
Generally, alcohols are lighter than water although the density increases with the increase in molecular mass.
vi. In toxicating effects:
Alcohols have in toxicating effects. Methanol is poisonous and is not good for drinking purposes. It may cause blindness and even death. Ethanol has been used for drinking purposes.
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Hydrogen Bonds
10.2 Chemical Properties of Ethanol
i. Combustion of Ethanol
Ethanol burns with a pale blue, non-luminous flame to form carbon dioxide and steam.
C2H5OH + 3O2 2CO2 + 3H2O Ethanol
ii. Oxidation of Ethanol Ethanol is oxidised
with acidified Potassium Dichromate, K2Cr2O7, or with acidified Sodium Dichromate, Na2Cr2O7, or with acidified potassium permanganate, KMnO4,
to form ethanal, (i.e. acetaldehyde).
[O] C2H5OH CH3CHO + H2O Ethanol Ethanal
The ethanal is further oxidised to ethanoic acid (i.e. acetic acid) if the oxidising agent is in excess.
[O]CH3CHO CH3COOH
Ethanal Ethanoic Acid
The oxidising agent usually used for this reaction is a mixture of sodium dichromate or potassium dichromate and sulphuric acid which react together to provide oxygen atoms as follows.
iii. Dehydration of Ethanol When ethanol is mixed with concentrated sulphuric acid with the acid in excess and heated to 170oC, ethylene is formed. (One mole of ethanol loses one mole of water)
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H2SO4 + C2H4 + H2O
C2H5OH 170 oC
When ethanol is mixed with concentrated sulphuric acid with the alcohol in excess and heated to 140 degC, diethyl ether distils over (two moles of ethanol loses one mole of water) .
H2SO4 +
2 C2H5OH C2H5OC2H5 + H2O 140 deg
iv. Reaction of Ethanol with Sodium
Sodium reacts with ethanol at room temp to liberate hydrogen. The
hydrogen atom of the hydroxyl group is replaced by a sodium atom, forming
sodium ethoxide.
C2H5OH + Na C2H5ONa + (H2)
Apart from this reaction, ethanol and the other alcohols show no acidic properties.
v. Dehydrogenation of Ethanol:
Ethanol can also be oxidised to ethanal (i.e. acetaldehyde) by passing its
vapour over copper heated to 300oC. Two atoms of hydrogen are eliminated
from each molecule to form hydrogen gas and hence this process is termed
dehydrogenation.
C2H5OH CH3CHO + H2 Ethanol Ethanal
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vi. Esterification of Ethanol:
Ethanol, C2H5OH, reacts with organic acids to form esters.
H(+)
C2H5OH + CH3COOH CH3COOC2H5 + H2O Ethanol Ethanoic Ethyl Water
Acid Acetate
vii. Halogenation or Substitution of Ethanol with PCl5 :
Ethanol reacts with phosphorus pentachloride at room temperature to form
hydrogen chloride, ethyl chloride (i.e. chloroethane) and phosphoryl chloride.
viii. Halogenation or Substitution of Ethanol with HCl:
Ethanol reacts with hydrogen chloride to form ethyl chloride (i.e.
chloroethane) and water. A dehydrating agent (e.g. zinc chloride) is used as
a catalyst.
ZnCl2
+ C2H5OH + HCl C2H5Cl + H2O Ethanol Ethyl
Chloride
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11.Uses of Ethyl Alcohol:
i. As a fuel:The largest single use of ethanol is as a motor fuel and fuel additive. Ethanol may also be utilized as a rocket fuel, and is currently in lightweight rocket-powered racing aircraft. The US uses Gasohol (max 10% ethanol) and E85 (85% ethanol) ethanol/gasoline mixtures.
ii. Antiseptic:Ethanol is used in medical wipes and in most common antibacterial hand sanitizer gels at a concentration of about 62% v/v as an antiseptic. Ethanol kills organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores.
iii. Feed stock:Ethanol is an important industrial ingredient and has widespread use as a base chemical for other organic compounds. These include ethyl halides, ethyl esters, diethyl ether, chloroform, iodoform, acetic acid, ethyl amines, and, to a lesser extent, butadiene.
iv. Treatment for poisoning by other alcohols:Ethanol is sometimes used to treat poisoning by other, more toxic alcohols, in particular methanol and ethylene glycol. Ethanol competes with other alcohols for the alcohol dehydrogenase enzyme, lessening metabolism into toxic aldehyde and carboxylic acid derivatives, and reducing one of the more serious toxic effect of the glycols to crystallize in the kidneys.
v. Solvent:Ethanol is miscible with water and is a good general purpose solvent. It is found in paints, tinctures, markers, and personal care products such as perfumes and deodorants.
vi. It is used in scientific instruments such as thermometers and spirit levels.
vii. It is used in manufacture of alcoholic beverages.
viii. It is used as antifreeze in automobile radiators.
ix. It is used as a preservative for biological specimens.
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12. Different Grades of Ethyl Alcohol:
Ethyl alcohol is one of the most important raw materials which are quite frequently used. It is solid in different grades of purity for different purposes. These are described below:
i. Absolute alcohol:It is the 100% pure ethanol. The fermentation of carbohydrates gives ethanol containing water. The fractional distillation of aqueous solution of ethanol gives a constant boiling azeotropic mixture which contains 95% ethanol. To get 100% ethanol a small amount of benzene is added with azeotropic mixture and then distilled. The first fraction (at 337.8 K) consists of water, ethanol and benzene. After all water is removed, the second fraction (at 341.2 K) consists of benzene and ethanol. Finally, pure ethanol is distilled as the last fraction (351.1 K).
ii. Methylated spirit or denatured alcohol:It is a 95% ethyl alcohol. To avoid the misuse of alcohol meant for industries for drinking purposes, it is made unfit by adding methanol, pyridine etc. the process is called denaturing of alcohol and the alcohol, thus obtained is called methylated spirit and can be used for non drinking purposes and particularly in industries.
iii. Power alcohol:It is a mixture of 20% ethanol and 50% gasoline. Since alcohol does not mix with petrol therefore a third solvent such as benzene, ether or (tetrahydronapthalene) is added. Due to the increased world consumption of petrol generally remains in a short supply. The use of power alcohol as a substitute for gasoline has promised bright future in India because we can manufacture large quantities of alcohol from molasses.
iv. Alcoholic Beverages:Liquors used for drinking purpose contain alcohol as the principal intoxicating agent. These are also called alcoholic beverages. They are prepared from different substance and contain different percentages of alcohol. There are mainly two types of beverages: distilled and undistilled. Undistilled beverages are prepared from grapes and other fruits juices and are called wines. The liquors obtained by distillation have higher alcoholic contents and have different trade names such as whisky, rum, brandy, gin, etc.
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13. By-Products in Ethyl Alcohol production:
Plants that produce ethanol, corn oil, and corn sweeteners also produce by-products in large quantities, and these by-products are employed successfully by beef producers as a more affordable feed alternative for cattle.
i. Carbondioxide (CO2) is a co-product of drymill ethanol production. Carbon dioxide is present during the fermentation stage of ethanol production, and many ethanol plants collect that carbon dioxide and market it as co-product. The carbon dioxide is cleaned of any residual alcohol, compressed, and sold to other industries. Carbon dioxide is used to carbonate beverages, to manufacture dry ice, and to flash freeze meat. CO2 is also used by paper mills and other food processors.
ii. Dried Distillers Grain ( DDG):
Distillers grain is an important co-product of drymill ethanol production. Drymill ethanol production process uses only the starch portion of the corn, which is about 70% of the kernel. All the remaining nutrients - protein, fat, minerals, and vitamins - are concentrated into distillers grain, a valuable feed for livestockIt is created from drying the mash after all useful ethanol has been extracted it is used as feed for cattle. Also DDGS is a soluble version made by adding water which is more easily consumed by cattle. “DDGS is a high quality feedstuff ration for dairy cattle, beef cattle, swine poultry,and aquaculture.
iii. Straw is another important co-Product from cereals and has been used for centuries for various uses. It has mostly been used for animal feed although recent uses include bio fuels in the lignocellulosic path to bioethanol. It can be used as a substrate for bio gas production through anaerobic digestion.
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