Biomedical Engineering Reference
In-Depth Information
Cx enzyme
Unsolvable
cellulose
Unsolvable and solvable
cellulose oligosaccharide
C1 enzyme
Cellobiose
CB enzyme
Glucose
Fig. 3.1
Synergetic degradation model [
44
]
Fig. 3.2
Possible ways of
enzymatic hydrolysis of
cellulose [
45
]
Cellulose
CBH I and CBH II
CBH I and CBH II
Cellodextrin
Cellobiose
EG I and EG II
Glucose
chain, and exoglucanase II (CBH II) cuts the nonreducing end of the cellulose chain.
The synergistic effect occurs only in the hydrolysis of natural cellulose, but not
CMC and hydroxyethyl cellulose (HEC). Enzymatic hydrolysis of endogluconase
and exogluconase is a heterogeneous reaction, and the hydrolysis of cellobiose
catalyzed by
-glucosidase is a homogeneous reaction. The enzymatic hydrolysis
efficiency of endogluconase is high for CMC but low for MCC. However, exoglu-
canase has high enzyme activity for MCC but low activity for CMC [
45
].
A hydrogen bond is an important force for maintaining the high-level structure
of protein and cellulose, and it is also the initial point of cellulose degradation by
cellulase [
46
]. At different pH environments, the proton state of hydrophilic layer
group of enzyme molecule will change, affecting the hydrogen-bonding state and
the higher-order structure of the enzyme molecule, leading to changes in the binding
activity of enzyme and substrate or the catalytic activity [
47
]. Gao et al. pointed
out that although considerable research on the cellulase degradation mechanism
has been carried out on a molecular level, the degradation mechanism of natural
crystalline cellulose has not been clarified because the effect of aggregation structure
on the degradation of the supramolecular structure of cellulose molecules has been
neglected [
48
]. Now, in the most popular theory, it is considered that first under the
effect of nonhydrolyzable enzymes that can hydrolyze a cellulose chain or hydrogen
bond, intrachain and interchain hydrogen bonds in the natural cellulose chain are
“
