**4.3 Fermentation**

Fermentation is the biological process using microorganisms to convert sugar and starch into ethanol. The production of bio-ethanol from starch-containing cereals typically includes the following five steps [15]:


*Alcohol Fuels: Current Status and Future Direction DOI: http://dx.doi.org/10.5772/intechopen.89788*

In Brazil, bio-ethanol is produced from sugar cane. Sugar cane is a sugar-bearing crop, and it is readily converted into ethanol by fermentation with yeast. Harvested sugar cane is thoroughly washed and crushed into pieces, the juice is extracted, and finally it is converted into sugary juice, which is further fermented by yeast. During the process, hydrous alcohol is produced by non-dehydration process and anhydrous one by dehydration process. Anhydrous ethanol is mixed with gasoline for the prevention of phase separation, and hydrous alcohol is used as fuel for all kinds of vehicles. The process wastes during the washing and crushing are again utilized as a boiler fuel to generate steam and electricity for subsequent ethanol production. In addition, for each ton of bio-ethanol, 1 ton of GMO-free, high-protein animal feed can be produced.
