Biomedical Engineering Reference
In-Depth Information
Fig. 1.2
Enzymatic
hydrolysis rate of cornstalk in
different parts
1.0
0.9
groundleaf
groundshell
groundcore
groundnode
leaf
shell
core
node
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
10
15
20
25
30
35
40
45
50
55
60
65
70
Enzymatic hydrolysis time / h
To resolve the problem of low-value utilization of straw used as a whole, my
research group from the Institute of Process Engineering (IPE), Chinese Academy of
Science (CAS) deeply studied the difference of each part of the cornstalk regarding
chemical composition, physical properties, and cellulase hydrolyzation [
14
]. From
the chemical composition, the cellulose content in the skin was the highest
(36.66 %) and had a significant difference compared to other parts. Hemicellulose
content in the leaves was the highest (33.86 %), and lignin was mainly concentrated
in the skin and knot, with contents of 14.23 and 12.52 %, respectively. Ash was
mainly concentrated in leaves (11.63 %) and was significantly different from the
content of other parts. Straw fiber had a remarkable morphological difference. The
content of microfibrils and hybrid cells was up to about 40-50 %, and fiber cell
content was about 40-70 %. Wood has a low content of hybrid cells and a high
content of fiber cells. For example, the fiber cell contents in hardwood and softwood
were 60-80 and 90-95 %, respectively. The enzymatic hydrolysis rate of different
parts of straw also showed inhomogeneity. The enzymatic hydrolysis rate of the
core, after enzymatic hydrolysis for 24 h, was up to 88.32 %, which was 28.33 %
of the leaves under the same hydrolysis conditions (Fig.
1.2
). Overall, compared to
wood, the cellulose and lignin contents of corn stover are relatively low, and the
hemicellulose and ash contents are relatively high. Meanwhile, the distribution of
chemical components differs from different parts of straw. In wood, the three major
components are mainly concentrated in the trunk (xylem), with a high content of
cellulose (higher than 45 %) and lignin (higher than 20 %) but a low hemicellulose
(typically less than 20 %) and ash (lower than 1 %) content.
The inhomogeneity results in the chemical and structural complexity of natural
lignocellulose and leads to obvious differences in the conversion process. The
inhomogeneity on bioconversion performance is a key factor that makes the high-
value utilization of lignocellulose difficult. However, the complex composition and
inhomogeneous characteristics of natural lignocellulose provide it the potential to
