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Karnataka.
3. Introduction:
Alcohol chemically ethanol (C2H5OH) produced by fermentation.
Brazil was the first country to produce ethanol in large scale by
yeast fermentation utilizing sugarcane.
Alcohol used as motor fuel is referred to as green petrol.
4. History:
For centuries alcohol has always played an important, and
sometimes decisive role in warfare.
Back in the days of Ancient Greece and later Ancient Rome it
was quite normal to give soldiers a daily ration of alcohol.
5. Microorganisms used for alcohol production:
Yeast: Saccharomyces cerevisiae (Sugar)
Bacteria: Zymomonas mobilis (Starch)
The type of organism chosen mostly depends on the nature of
the substrate.
6. Raw Materials:
There are large number of raw materials that can serve as
substrates for alcohol fermentation.
Sugary materials: Glucose, Sucrose, Molasses.
Starch materials: Wheat, rice, Maize and potato.
Cellulose materials: Wood and agricultural wastages.
7. Pre-treatment of raw materials:
The sugary materials not require pre-treatment.
While the cellulosic materials need extensive pre-treatment.
The cellulose materials subjected to acidic or enzymatic hydrolysis
to release monosaccharide units.
8. Preparation of Nutrient solution or media:
Molasses is used for fermentation, it is diluted with water and
sugar concentration maintained between 10-18% per 100 ml.
Ammonium salts like ammonium sulfate or phosphate are add
to the nutrient solution or media.
The pH of the medium adjusted to 4-5 adding sulfuric or lactic
acid.
9. Preparation of inoculum:
The selected microorganism isolated in pure form and cultured
in small size flask or fermenters.
Under controlled condition the size of the inoculum increases
which can be used for inoculation.
10. Biosynthesis of ethanol:
Glucose break down into Pyruvate. (Glycolysis)
Under anaerobic conditions pyruvate converted in to
acetaldehyde by the enzyme pyruvate decarboxylase.
Acetaldehyde form alcohol by the enzyme Alcohol
dehydrogenase.
12. Fermentation:
Batch fermentation generally used now at most places continuous
fermentation is used.
Because yield is very high when compare to batch fermentation.
13. The ideal pH is 4.0-4.5.
The initial temperature is 21-27 °C.
The temperature raises during the fermentation up to 30 to 37°C.
The fermentation process to be complete 2-3 days under these
conditions.
14. Glucose to alcohol conversion profile:
One gram of glucose converted in to 0.511 grams of ethanol.
It is estimated that for 100g pure glucose:
48.5 g of ethanol
46.5 gms of CO2 and
1.3g of biomass is produced after fermentation yeast.
15. Recovery of ethanol:
The cell mass is separated by centrifugation.
Ethanol is purified by successive distillations.
It is easy to obtain 95% ethanol concentration.
17. It is generally prepared from malted barley but other starchy
grains, e.g..Wheat, maize, rice are also used as raw materials.
Yeasts especially Saccharomyces cerevisiae are used in the
fermentation process.
Beer Fermentation:
18. Major steps are involved in the manufacture of beer:
Step: 1: Malting:
The malt is prepared by first soaking the grains in water and
then allowing it to germinate at 17°C.
After the germination is completed, the grains are dried at
65°C.
19. Mashing:
After malting, the pure barley malt is mixed with other grains such
as corn, rye, wheat, etc.
It is called ‘ground malt’.
The ground malt mixed with warm water at about 70°C.
.
20. Mashing brings about partial hydrolysis resulting in the digestion
of starch and protein;
The partially hydrolysed solution of mash is filtered and this
filtrate is called ‘beer wort’.
Beer wort serves as a rich nutrient medium for the
microorganisms.