Ethanol can be produced chemically from petroleum or microbiologically from fermentable carbohydrates. It is produced in the anaerobic fermentation of glucose by Saccharomyces cerevisiae. Corn & other material must undergo saccharification before they can be fermented. The carbohydrate in corn starch is enzymatically released by treating the ground corn with a amylase and gluco-amylase. Molasses made from the juices from sugarcane are fermented directly.
Ethanol is produced in batch fermentation system using either hydrolyzed starch or molasses. The cells generated in the process are removed by sedimentation or centrifugation before the ethanol is purified by distillation. A simplified diagram of ethanol production is shown below:
The manufacture of alcoholic beverages represents one of the largest industrial applications of microbial activity. In brewing , both carbon dioxide and ethanol formed as a result of fermentation become desirable products. Further, in brewing, the growth of yeast in a sugary medium should take place under anaerobic conditions; as, otherwise fermentation is inhibited. Of the many alcoholic beverages wine and beer are produced in the largest quantities. The raw materials used and the processes employed in manufacturing them are different.