INDUSTRIAL ALCOHOL PRODUCTION
The production of industrial alcohol, ethanol become commercially feasible on a large scale after 1906 when the Industrial Alcohol Act was passed. This act allowed the sale of tax-exempt alcohol, if it has first denatured to prevent its use in various Alcohol beverages. Industrial Alcohol is commonly employed as a solvent and to a lesser extent as a raw material for chemical synthesis. Smaller amounts are also used as a motor fuel like gasoline.
Choice of fermentation microorganism for the alcohol production depends upon the type of carbohydrate employed in the medium. For example if starch and sugar are raw materials in the medium then specially selected strains of Saccharomyces crevisiae are utilized.
Production from Lactose of whey is accomplished with Candida pseudotropicalis. If it is sulfur waste liquor fermentation the Candida utilis is the best organism, because of its ability to ferment pentoses. So particular strains of these various organisms actually employed for the fermentation are selected for several properties.
They must grow rapidly, have higher tolerance to the high concentartions of sugar but at the same time they must be able to produce much larger amounts of alcohol and be resistant to the produced alcohol.
- The media for the commercial production includes:
- Blackstrap Molasses / Corn (Blackstrap molasses has greater use)
- Sulfite waste liquor
- Wood Wastes
For Molasses fermentation , molasses must be diluted with water to a sugar conc. between 10 -18%. Concentrations greater than 20% are not employed as they could be detrimental to yeast. The pH of the medium is set between 4 -5 by adding sulfuric acids or lactic acids, or by employing Lactic acid bacteria to bring initial lactic acid fermentation. Microbial contaminants are usually inhibited by the low pH, high sugar conc. and anaerobic conditions of the fermentation and by the high alcohol production by the yeast.
Starchy media such as corn, rye and barley must undergo initial starch hydrolysis. This can be accomplished by mashing with barley malt, by addition of dilute acids or by utilizing fungal amylolytic enzymes (Aspergillus and Rhizopus).In most of the cases, malt is used to accomplish hydrolysis of starch By mixing 30% barley and 70% corn with water and carry on the mashing procedures similar to the wine or nbeer making procedures.
Fermentation is carried out in large reactors at a temperature between 21 – 27oC, but heat evolution might raise the temperature to 30oC, so cooling coils are used to bring the temperature down. Fermentation lasts for about 2-3 days, but actual time period depends upon the substrate utilized and temperature. The fermentation broth at completion of fermentation ranges from 6 -9 percent alcohol by volume and this alcohol reflects the yield 0f 90 -98% theoretical conversion of substrate sugar to alcohol.So yileds should not be confused with “proof” as proofing means alcohol concentartion designation and it will be twice the percentage in vol of ethanol as dissolved in water e.g. 70% ethanol is 140 proof.