Biomedical Engineering Reference
In-Depth Information
Cellulolytic Enzyme Production
and Enzymatic Hydrolysis
for Second-Generation
Bioethanol Production
Mingyu Wang, Zhonghai Li, Xu Fang, Lushan Wang and Yinbo Qu
Abstract Second-generation bioethanol made from lignocellulosic biomass is
considered one of the most promising biofuels. However, the enzymatic hydrolysis
of the cellulose component to liberate glucose for ethanol fermentation is one of
the major barriers for the process to be economically competitive because of the
recalcitrance of feedstock. In this chapter, the progress on the understanding of the
mechanisms of lignocellulose degradation, as well as the identification and opti-
mization of fungal cellulases, cellulolytic strains, and cellulase production is
reviewed. The physiologic functions and enzymatic mechanisms of two groups of
enzymes involved in lignocellulose degradation, cellulases and hemicellulases, are
discussed, and the synergism of the cellulase components during lignocellulose
degradation is addressed. Furthermore, the methods for screening filamentous
fungal strains capable of degrading lignocellulose are evaluated and the production
of cellulases by these fungal strains is discussed. Aside from traditional muta-
genesis for improving the secretion level and enzymatic activities of cellulases
from filamentous fungal species, genetic engineering of strains and protein engi-
neering on cellulase molecules are also highlighted.
Keywords Bioethanol Cellulases Hemicellulase hydrolysis Lignocellulose
Contents
1
Introduction..........................................................................................................................
2
2
Lignocellulose Biodegradation............................................................................................
3
2.1
Cellulolytic Enzymes..................................................................................................
3
2.2
Mechanism of Cellulose Biodegradation ...................................................................
5
2.3
Factors Affecting Enzymatic Hydrolysis ...................................................................
9
M. Wang Z. Li X. Fang (
) L. Wang Y. Qu
State Key Laboratory of Microbial Technology,
Shandong University, Jinan 250100, China
e-mail: fangxu@sdu.edu.cn
&
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