Biomedical Engineering Reference
In-Depth Information
Table 1.1
Chemical composition of lignocellulose (%, dry material) [
10
]
Water-soluble
composition
Species
Cellulose
Hemicellulose
Lignin
Wax
Ashes
Wheat straw
4.7
38.6
32.6
14:1
1.7
5:9
Rice straw
6.1
36.5
27.7
12:3
3.8
13:3
Perennial ryegrass
4.1
37.9
32.8
17:6
2.0
3:0
Barley grass
6.8
34.8
27.9
14:6
1.9
5:7
Oat grass
4.6
38.5
31.7
16:8
2.2
6:1
Cornstalk
5.6
38.5
28.0
15:0
3.6
4:2
Corncob
4.2
43.2
31.8
14:6
3.9
2:2
Spanish grass
6.1
35.8
28.7
17:8
3.4
6:5
Sugar beet pulp
5.9
18.4
14.8
5:9
1.4
3:7
Bagasse
4.0
39.2
28.7
19:4
1.6
5:1
Oil palm fiber
5.0
40.2
32.1
18:7
0.5
3:4
Coke fiber
3.7
60.4
20.8
12:4
0.8
2:5
cellulose, and lignin. Meanwhile, the loose structure caused by the presence of a
large number of thin-walled cells makes the cornstalk cores show a strong water
absorption capacity. Therefore, cornstalk cores are suitable for use as a substrate
for macrofungi fermentation and caramel production. Cornstalk leaves are mainly
composed of epidermis and mesophyll. The ash content of the leaves is high because
of the distribution of a large number of silicon cells in the epidermis. In the
mesophyll, a vascular bundle is surrounded by mesophyll cells. Because of the low
vascular bundle content in the leaves, the cellulose content in leaves also is relatively
low. At the same time, the curling and stretching of the leaf is related to not only
the motor cell but also the low degree of lignification. Therefore, compared to other
parts of straw, the leaf is more appropriate for livestock feed because of its better
palatability. The lignin content of the node is high because of its high lignification
degree.
1.2.2.2
Significant Differences in Chemical Composition
Straw has a large amount of hemicellulose and a relatively high ash content (higher
than 1 %). Taking rice straw as an example, the main components in the cell wall
of dry rice straw are cellulose, hemicellulose, and lignin. In addition, there are
minerals, cutin, and suberin in the cell wall. Their complex structure forms a tight
recovery system for straw. In rice straw, the chemical composition also contains
crude protein (mainly embodied in the cell wall in the form of structural proteins)
and acids (including p-hydroxybenzoic acid, vanillic acid, coumaric acid, ferulic
acid, etc). In general, the content of cellular components and cell wall material in
the straw accounts for 21 and 79 % (including 33 % cellulose, 26 % hemicellulose,
7 % lignin, and 13 % silicide), respectively.
