Fermentation is a biological process for ethanol production. The microorganism such as yeasts is the best choice for ethanol production. There are three kinds of processes used in the ethanol production from sugarcane straw. Separate hydrolysis and fermentation is the first process of fermentation where lignocellulosic hydroly­sis and ethanol fermentation have been done separately. Another two methods are simultaneous saccharification and fermentation (SSF) and simultaneous saccharifi­cation and cofermentation (SSCF). To obtain the desired ethanol yields from sugar­cane straw hydrolysates, it is essential that the hemicellulose fraction should be fermented with the same conversion rate for getting the maximum ethanol produc­tion (Lin and Tanaka 2006). Hemicellulose hydrolysate contains pentose and hex — ose sugars. The different types of yeast, fungi, and bacteria can assimilate pentose sugar by conversion of sugarcane straw hydrolysate.

16.5.2 Distillation of Ethanol

The final medium of ethanol production is composed of water and ethanol (Huang et al. 2008). Ethanol recovery is necessary from a fermented substrate. The water and ethanol cannot be separated by conventional method. There are three steps for ethanol purification such as distillation, rectification, and dehydration. The dehy­dration method can be used for producing high concentrated ethanol. Huang et al. (2008) reported that a dehydration process can be realized through azeotropic distillation, extractive distillation, liquid-liquid extraction, adsorption, or some complex hybrid separation methods.