氏
名
：
高
子晴
論文題目
：
Evaluation on the enhancing enzymatic hydrolysis of lignocellulose
（リグノセルロースの酵素糖化反応の活性化に関する研究）
区
分
：
課程博士
（甲）
論
文
内
容
の
要
旨
The bioconversion of renewable resources, especially lignocellulosic residues, into useful chemicals
and fuel ethanol is a worldwide challenge for biotechnology. Lignocellulose bio-refining generally involves
three main steps: pretreatment, enzymatic hydrolysis, and fermentation.
Commercialization of bio-ethanol
is hindered by the high cost of pretreatment process and high cost of cellulase enzymes required for
lignocellulose hydrolysis. Therefore, choose a suitable pretreatment method and screen the fungi or bacterial
with high-efficient hydrolytic multienzyme system are the necessary approach for successful
commercialization.
In this study, we set forth the methods that enhancing the enzymatic hydrolysis of lignocellulose in two
directions:
(1) Choose biological pretreatment method that using brown-rot fungus Gloeophyllum trabeum KU-41
to pretreat corn stover for efficient hydrolysis. To gain a deeper understanding of the mechanisms of
brown-rot fungus pretreatment, the fungal-pretreated corn stover was evaluated in detail, including the
lignin and structural carbohydrate contents, cellulose crystallinity, initial adsorption capacity of cellulase,
SEM and specific surface area. G. trabeum has an efficient degradation system, and the results indicated that
the conversion of cellulose to glucose increases as the accessibility of cellulose increases due to the partial
removal of xylan and the structure breakage of the cell wall.
(2) To isolate and screen microorganisms to produce considerable quantities of β-glucosidases. A potent
β-glucosidases-producing fungus SIID11460 was isolated and identified as Fusarium proliferatum. Under
optimized conditions, F. proliferatum SIID11460 produces β-glucosidases with high specific activity (16.5
U/mg-protein). Moreover, a new method was built up that combines zymogram, gel purification and
SDS-PAGE.
Using this method, it was proved that F. proliferatum SIID11460 could express varied
β-glucosidases in respond to varied carbon sources.
The present research might be a promotion for bio-ethanol production. G. trabeum was applied to
pretreat corn stover with enhancing saccharification significantly. This pretreatment method can be further
explored as an alternative to the thermochemical pretreatment method. β-glucosidases produced by F.
proliferatum SIID11460 with high catalytic activity could apply for hydrolysis of lignocellulose for
bio-ethanol production.