Fermentation Industry
The fermentation (Latin: to boil) formerly stood for decomposition of food stuffs usually accompanied by evolution of gas. The fermentation of sugars to alcohols and carbon dioxide by yeast is one of the oldest example.
A fermentation can be defined as, a process in which chemical changes are brought about in an organic substrate (carbohydrates, fat, proteins, hydrocarbon etc.) through the action of the biochemical catalyst known as 'enzymes' produced by specific types of living micro-organisms.
In our daily life, we see many complex chemical reactions, which are brought about by the agency of living organisms. e.g. souring and meat etc. All these processes are called 'fermentation processes' in which complex organic material is broken down into simpler substances and decomposition is brought about by the action of living organisms, which secrete the enzyme catalyst suitable to the process.
Importance of Fermentation:
Important unique products of industrial fermentations are -
1) Alcoholic products like - ethanol, wine, beer, spirit etc.
2) Antibiotics like - Penicillin, streptomycin, tetracyclines, chloramphenicals, erythromycin etc.
3) Vitamins like - Riboflavin, vitamin A, vitamin B12 etc.
4) Organic acids like - Lactic acid, citric acid, acetic acid- vinegar, fumaric acid etc.
5) Amino acids like - Lyzine, glutamic acid etc.
6) Sorbose for Vitamin C, baker's yeast, fodder yeast.
7) Single cell proteins from hydrocarbons and cellulosic waste.
Basic requirements of Fermentation Process:
Success of fermentation process on the industrial scale depends on number of factors. According to silcox and Lee the five basic requirements for good fermentation process are:
a) Micro-organism:
The selected micro-organism must be readily propagated and must maintain uniform biological and biochemical characteristics, thereby giving predictable yields.
b) Raw material:
The raw material must be cheap and easily available in uniform composition.
c) Time:
The time required for fermentation should be reasonable (i.e. high fermentation rates are desirable).
d) Recovery:
The recovery of the product in the pure form should be easy.
e) Economy:
The process should be more economic than the chemical synthetic process or should manufacture a unique product (e.g. wine, beer, antibiotics) which is in demand, e.g.citric acid, lactic acid, penicillin, streptomycin etc. have no serious competition from synthetic process.
Factors favorable For Fermentation:
The process of fermentation is influenced by following factors:
a) Temperature:
The temperature should be neither too low or not too high, because enzymes are destroyed at very high temperature and become inactive above 80°C. Similarly the fermentation process is very slow below 20°C. Generally an optimum temperature of 30-50° is most favorable for fermentation.
b) Aeration:
Fermentation process usually proceed well only in the presence of air.
c) Concentration:
High concentration of a solution renders an enzyme inactive. Therefore solutions used for fermentation should be sufficiently dilute to favour the process.
d) Presence of other substances:
Certain inorganic salt solutions acts as food for the ferment cell.
e) Absence of preservatives:
Preservatives are those substances which destroy the ferments and retard (stop) the fermentation reaction. Hence these substances should be absent.
f) pH conditions:
The pH has great influence on the rate of fermentation. The bacteriologist has developed acid-loving yeasts not liking acidic conditions, do not flourish.
Actually fermentation under controlled conditions involve chemical conversions. Many chemical reactions caused by micro-organism are very complex and cannot be easily classified, hence the concept of fermentation itself as a chemical conversion has been developed.
Manufacture of Industrial Alcohol:
Industrially ethyl alcohol is manufactured from a) Molasses b) Food grains c) Friuts and d) Hydrocarbons.
A) Ethyl alcohol from Molasses:
Actually molasses is a dark coloured viscous liquid left after the crystallization cane sugar from cane juice. It contains 50-55% total sugar of which 35-40% is cane sugar or sucrose.
Molasses is converted into ethyl alcohol by means of yeast which produces enzymes, invertase and zymase. The enzyme invertase hydrolyses cane sugar into glucose and fructose while the enzyme zymase decomposes glucose and fructose (Monosaccharides) into ethyl alcohol and carbon dioxide.
B) Ethyl alcohol from food grains:
To obtain ethyl alcohol from food grains following steps:
1) Malting:
Malt is prepared from the barley by soaking it in water, allowing it to germinated for 20 days and drying it carefully under regulated conditions forming a malt. Although malting is an integral part of brewing process, it is only rarely carried out in the brewery. It is mostly Carried out in a separate industry.
2) Mashing:
The malt contains a considerable amount of starch and a small amount of sugar, together with the enzymes diastase.
a) The malt is crushed and mixed with hot water and raw grain (rice, wheat, barley, maize) or potato starch is then added.
b) The temperature is maintained between 40-60°C.
c) As a result of fermentation in presence of enzyme diastage starch is converted into maltose or malt sugar. This process is called mashing.
3) Fermentation:
1) After the completion of mashing, the sweet liquid or worth is then transferred to a fermenting tank.
2) To this wort, yeast is added.
3) The enzyme maltose present in the yeast converts maltose into glucose.
4) Then the enzyme zymase present in the yeast converts glucose into ethyl alcohol and carbon dioxide.
5) Small amounts of higher alcohols, succinic acid and glycerine etc. are also produced.
d) Distillation :
Ethyl alcohol is separated from the mixture by fractional distillation method. Scotch whiskey is prepared from barley malt.
C) Ethyl alcohol from fruits (wine) :
Wines are prepared by fermentation of fruit juices. The chief juice is that of grapes. Wines are classified as natural (contain 7-14% alcohol), fortified (contain 14-30% alcohol), sweet or dry and still or sparking.
To obtain wine from grapes involves following steps:
a) Preparation of Must:
The grape juice contains glucose, fructose and various acids (tartaric acid). The skin of the grapes contain tannin, various essential oils or a colouring matter. When grapes are crushed in crusher all above materials come into the juice. The seeds and part of the steams are removed. The juice extracted from wooden roller (crusher) is called must.
b) Fermentation:
The must is first fermented into ethyl alcohol. After first active fermentation is over, the new wine is filled full into casks, which are loosely closed in order to prevent the conversion of alcohol into acetic acid. It is kept for 3-4 months. During this period, the yeast settles down and tartaric acid along with various salts and colouring matters, separate out as argol. It is then filtered.
c) Ripening:
The clear wine is then allowed to ripe for 2-4 years. During ripening tanning and some other impurities are precipitated. In this period alcohol and fusel oil react with acids present to form esters. These esters give characteristics flavour to the wine.
d) Bottling:
After ripening the wine is bottled. The quality of wine varies from place to place and varieties of group.
D) Ethyl alcohol from hydrocarbons:
The process involve two routes-
a) Liquid phase hydration;
In this process first ethylene is absorbed in conc. H2SO4, forming ethyl sulphuric acid (ethyl hydrogen sulphate) and diethyl sulphate.
C2H4 + H2SO4 = C2H5HSO4
C2H5HSO4 +C2H4 = (C2H5)2 SO4
These ethyl hydrogen sulphate and diethyl sulphate on treatment with water hydrolyse to ethyl alcohol and H2SO4.
b) Gas phase hydration:
Water adds to alkene in presence of proton donar (acid) supported on a carrier to yield alcohols.
The reaction is exothermic and favoured by low temperature and high pressure.
The conversion is also favoured by high ratio of ethylene to water.
Industrial Fermentation | Definition, Process, & facts - Chemosmart
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