ABSTRACT
Abstract .................................................................................................................. 142 10.1 Introduction .................................................................................................. 142
10.1.1 Cellulases ........................................................................................ 142 10.1.2 Hemicellulases ................................................................................ 144
10.2 Microbial Lignocellulolytic Machinery: Complexed and Noncomplexed Systems ................................................................................ 145 10.3 Microorganisms Producing Cellulases and Hemicellulases ........................ 146
10.3.1 Cellulases ........................................................................................ 146 10.3.2 Hemicellulase ................................................................................. 147
10.4 Regulation of Cellulase and Hemicellulase Gene Expression ..................... 148 10.5 Molecular Approaches in Improving Production and Properties of Cellulases and Hemicellulases ..................................................................... 149 10.6 Bioprocesses for Cellulase and Hemicellulase Production .......................... 152
10.6.1 Cellulase Production ....................................................................... 152 10.6.2 Xylanase Production ....................................................................... 153
10.7 Assay of Cellulases and Xylanases............................................................... 154 10.8 Cellulases and Hemicellulases for Biomass Ethanol: Challenges for the Future ................................................................................................ 154 10.9 Conclusions .................................................................................................. 155 References.............................................................................................................. 156
Creating ethanol from biomass is considered to be one of the most valuable solutions to the increasing liquid fuel demand. The technology for generating fermentable sugars from lignocellulosic biomass is still not mature and is largely dependent on developments in cellulase enzyme technology since the most promising scheme for biomass hydrolysis involves the use of cellulose-and hemicellulose-degrading enzymes. The technology is receiving a renewed interest in the current scenario with increasing efforts to improve its efciency and cost effectiveness. Currently the major limiting factor in the commercialization of biomass to ethanol technology is the cost of cellulase enzymes, which is the major contributor to the production cost of bioethanol. Innumerable research efforts are directed towards understanding the fundamentals of microbial enzymes involved in biomass hydrolysis, and their production and applications. Proper exploitation of microbial sources for biomass-degrading enzymes requires in-depth understanding of their physiology, molecular biology, and strategies for fermentation. This chapter summarizes some of the current knowledge of microbial cellulase production and explores the avenues of its exploitation.
