Chapter 41 - New insights of cellulosic ethanol production from lignocellulosic feedstocks

Abstract

Worldwide studies on cellulosic ethanol production have grown with the increase in energy demand, and it has become a main area to which several governments, research groups, and industries pay attention. Ethanol is currently the most universal renewable fuel generated by microorganisms from different raw materials and wastes. Because of advancements in agricultural biotechnology, one can imagine cheap ethanol production on lignocellulosic feedstock. The “second-generation” bioethanol using lignocellulosic materials as raw materials is a promising substitute to the first-generation bioethanol. This chapter summarizes the various processes employed in the bioconversion of lignocellulose-derived biofuels. In the recent decades, incredible efforts were made to optimize the production of lignocellulose-derived fuel ethanol, which is economically feasible. In view of climate changes and exhaustion of fossil fuels, the transportation sector urgently needs oil substitutes. This chapter outlines the development of second-generation bioethanol, which is different from the first-generation fuels in that it uses lignocellulosic feedstock. Cellulosic biomass consists of cellulose, hemicellulose, and lignin and the technical stages involved in processes like pretreatment, enzymatic hydrolysis, fermentation, distillation and dehydration, are introduced. Lignocellulosic materials are employed as abundant raw materials to generate fuel ethanol at sustainable rate. After pretreatment, enzyme hydrolysis process may be conducted by separate hydrolysis and fermentation (SHF) or simultaneously saccharification and fermentation (SSF). However, there are some technical obstacles. For example, the pretreatment of lignocellulosic raw materials releases toxic inhibitors, the rate of removal of enzymes is reduced, and the simultaneous rapid fermentation of hexoses and pentoses needs to be resolved to effectively remove lignocellulose.