14
2 High-Efficient Anaerobic Fermentation Technology of Organic …
cellulose. Some specific acid, alkali and salt solutions can be dissolved easily by
entering crystalline structure of celluloses to generate solvent swelling. The main
purpose of the chemical pre-treatment is to dissolve cellulose, hemicellulose and
some lignoses through chemical reagents, thus improving the efficiency of anaerobic
fermentation of substrates.
(3) Biological method
The principle of biological pre-treatment is that microorganisms or bioenzymes act
on lignocellulose and their hyphae can dissolve waxy structure on the surface of
plants containing cellulose and massively reproduce and grow after entering the
plants. In the meanwhile, these including cellulase, hemicellulase, endo-xylanase
and exoglucanase are produced, which degrades lignocellulose, thus improving
utilization efficiency of substrates.
2.2 Pre-treatment Technologies of Anaerobic Fermentation
2.2.1 Hydrothermal Pre-treatment Technology of Putrescible
Wastes
In view of characteristics including high contents of water, fat and salt of putrescible wastes that are unfavorable for anaerobic fermentation, the hydrothermal pretreatment technology was used to research kitchen wastes. Through the research, the
influences of various parameters of hydrothermal pre-treatment on transformation
laws of substances, such as solid and liquid fat, protein and floating oil of kitchen
wastes were analyzed.
2.2.1.1 Influences of Hydrothermal Pre-treatment on Crude Protein
Crude protein is one of major objective products of transforming biomasses by using
the hydrothermal pre-treatment technology. Solubility of protein in water increases
as ionisation of water strengthens, while ionisation of water rises with growing temperature and pressure. Therefore, raising treatment temperature and shortening treatment time are important conditions for obtaining high-yield protein (Fig. 2.2). The
research showed that the content of crude protein rose after kitchen wastes underwent
hydrothermal pre-treatment at 80 and 120 °C. At this time, hydrolysis of colloid of
crude protein exerted no effects on higher structure of protein and hydrolysis degree
is low. In addition, some macromolecular substances, such as carbohydrate and lipid
in kitchen wastes were liquefied or leached higher than crude protein, so that the
content of crude protein increased. When temperature rose further, the effects of
hydrothermal pre-treatment on peptide bonds strengthened, which changed internal
structure and significantly increased solubility. Therefore, at 150 and 200 °C, the
2 High-Efficient Anaerobic Fermentation Technology of Organic …
cellulose. Some specific acid, alkali and salt solutions can be dissolved easily by
entering crystalline structure of celluloses to generate solvent swelling. The main
purpose of the chemical pre-treatment is to dissolve cellulose, hemicellulose and
some lignoses through chemical reagents, thus improving the efficiency of anaerobic
fermentation of substrates.
(3) Biological method
The principle of biological pre-treatment is that microorganisms or bioenzymes act
on lignocellulose and their hyphae can dissolve waxy structure on the surface of
plants containing cellulose and massively reproduce and grow after entering the
plants. In the meanwhile, these including cellulase, hemicellulase, endo-xylanase
and exoglucanase are produced, which degrades lignocellulose, thus improving
utilization efficiency of substrates.
2.2 Pre-treatment Technologies of Anaerobic Fermentation
2.2.1 Hydrothermal Pre-treatment Technology of Putrescible
Wastes
In view of characteristics including high contents of water, fat and salt of putrescible wastes that are unfavorable for anaerobic fermentation, the hydrothermal pretreatment technology was used to research kitchen wastes. Through the research, the
influences of various parameters of hydrothermal pre-treatment on transformation
laws of substances, such as solid and liquid fat, protein and floating oil of kitchen
wastes were analyzed.
2.2.1.1 Influences of Hydrothermal Pre-treatment on Crude Protein
Crude protein is one of major objective products of transforming biomasses by using
the hydrothermal pre-treatment technology. Solubility of protein in water increases
as ionisation of water strengthens, while ionisation of water rises with growing temperature and pressure. Therefore, raising treatment temperature and shortening treatment time are important conditions for obtaining high-yield protein (Fig. 2.2). The
research showed that the content of crude protein rose after kitchen wastes underwent
hydrothermal pre-treatment at 80 and 120 °C. At this time, hydrolysis of colloid of
crude protein exerted no effects on higher structure of protein and hydrolysis degree
is low. In addition, some macromolecular substances, such as carbohydrate and lipid
in kitchen wastes were liquefied or leached higher than crude protein, so that the
content of crude protein increased. When temperature rose further, the effects of
hydrothermal pre-treatment on peptide bonds strengthened, which changed internal
structure and significantly increased solubility. Therefore, at 150 and 200 °C, the