Using lactose hydrolyzing yeast under anaerobic conditions, whey can be con­verted into alcohol [137]. The system though made primarily for SCP production from whey, can also be employed for production of alcohol. Prehydrolyzed whey with b-galactosidase enzyme in which most of the lactose is hydrolyzed has been used as a substrate for alcohol production. Since the alcohol produced is taxed in a similar manner as the potable alcohol for use in the beverage industry, this proposition also becomes expensive [117]. Such alcohol for use as industrial alcohol or alcohol as a chemical should be taxed at different rates than used for potable beverage production.

9.7.11 Cassava Roots

Cassava roots are used as raw materials for the production of ethanol in some countries like Brazil. The alcohol produced from cassava roots was used as motor fuel, mixed with gasoline (upto 20% alcohol) for which no motor modification is required. It is also used as pure anhydrous ethanol, in which there is need to modify the carburetor and some other parts. Both result in less atmospheric pol­lution than the use of 100% gasoline. Commercial production of ethanol from cassava is obviously not new in some parts of Asia like India and China. In China, several factories are now using solid waste (bagasse) of the cassava starch industry for the production of ethanol [59].

The suitability of extractive fermentation as a technique for improving the production of ethanol from lactose by Candida pseudotropicalis over the con­ventional technique has also been examined [81, 82]. Using Adol 85 NF, extractive solvent, biocompatible with microorganisms, extractive fed-batch and conventional fed-batch systems were operated for 160 h and the extractive system showed a 60% improvement in lactose consumption and ethanol production with 75% volumetric productivity.

In the syngas platform, the biomass is subjected through a process called gasification. In this process, the biomass is heated with no oxygen or only about one-third the oxygen normally required for complete combustion. It subsequently converts into a gaseous product, which contains mostly carbon monoxide and hydrogen. The gas, which is called synthesis gas or syngas, can be fermented by specific microorganisms or converted catalytically into ethanol. In the sugar platform, only the carbohydrate fractions are utilized for ethanol production, whereas in the syngas platform, all the three components of the biomass are converted into ethanol [41].