Biomedical Engineering Reference
In-Depth Information
production of sodium glutamate were used to substitute for ammonium sulfate as
the nitrogen source during cellulase production, and a similar cellulase production
rate was observed [
112
].
The optimization of fermentation conditions has also been attempted to improve
cellulolytic enzyme production by Chinese scientists. Dong et al. [
92
] reported that
the CMCase production of P. decumbens JU-A10 was increased through response
surface analysis and that the productivity with Chinese sorghum straw as a carbon
source was significantly higher than that of corn stover. Yu and Koo [
113
]
increased cellulase production with T. reesei from 21.25 FPU/mL to 30.6 FPU/mL
through fed-batch culture and suggested that cell mass has a significant effect
on cellulase activity and productivity. Qu and Gao [
114
] used a mixed culture of
P. decumbens and Aspergillus sp. and improved the cellulolytic enzyme system
during solid-state fermentation.
4 Conclusions
The enzymatic hydrolysis of lignocellulosic biomass for the production of second-
generation bioethanol is considered one of the most promising approaches for
abundant and reliable biofuels, and it has therefore received attention from sci-
entists worldwide, including Chinese scientists. In this review, we have attempted
to summarize current understanding of the mechanism of lignocellulose degra-
dation, as well as the efforts to optimize the production of cellulases, the hydrolysis
of lignocelluloses, and the fungal strains that produce cellulases. As can be seen,
rendering of biomass recalcitrance is a complicated process that requires the
synergistic effort of multiple factors, including cellulases, hemicellulases, and
nonenzyme factors. Synergism was also discovered within each group of enzymes
and even within specific enzyme molecules. This process is still far from being
completely
understood;
new
factors
are
being
discovered
and
new
findings
regarding the mechanism of this process are being reported.
The oil crisis in the 1970s as well as the recent one have prompted scientific and
industrial efforts to search for a realistic substitute or at least a supplement for crude
oil. The rapid economic progress and improvement of living standards in China since
the 1980s demand a rapid increase in energy production. This has led to a shift in the
focus of the Chinese government and scientists to sustainable energy production,
including the development of technologies for second-generation bioethanol. In this
review, the efforts of Chinese scientists in the development of better enzymes, better
strains, and better approaches for lignocellulose-based bioethanol production has
been summarized. These efforts have dramatically increased the productivity and
efficiency and have decreased the costs of bioethanol production. Today, numerous
governments, institutions, and international corporations have initiated and succeeded
in searches for viable and economic protocols in the enzymatic hydrolysis of ligno-
celluloses. We are optimistic that industrial-scale production of second-generation
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