Trichoderma Strains Enzyme Production Culture And Its Specific Substrate Hydrolysis Process

Nowadays energy crisis exacerbated the emergency of fuel ethanol production by lignocelluloses hydrolysis. Cost of cellulase was always the bottleneck of lignocellulosic ethanol industrialization, which makes cellulase to be the key point among present studies. Steam-pretreated Lespedeza was selected as specific substrate. Cellulases were produced by four Trichoderma strains under various fermentation modes, media compositions and mutagenesis conditions. Cellulase was secreted by Trichoderma viride strain on different cellulosic media. Glucose yield, degree of polymerization, crystallinity index and photos scanned by the scanning electron microscopy of degraded steam-pretreated Lespedeza residues were studied to evaluate the hydrolysis capability of secreted cellulases to the specific substrate. Protein concentrations, filter paper activities (FPAs) andβ-glucosidase activities in the corresponding digests were determined to assay hydrolysis performance of cellulases towards the specific substrate. Influneces of surfactants on enzymatic activities and hydrolysis efficiency were evaluated.Highest FPA,0.36 FPU/mL, was detected from cellulase secreted by Trichoderma viride under liquid state fermentation after 15 d. FPAs of cellulases from Trichoderma pseudokoningii and Trichoderma koningii were 0.24 FPU/mL and 0.36 FPU/mL, respectively. FPA of cellulase secreted by Trichoderma reesei was 0.26 FPU/mL after 11 d. FPA of cellulase secreted by Trichoderma viride was 0.71 FPU/mL after 7 d at the condition of solid/liquid 1/3.5, C/N 5/1, initial pH 3.5. FPA of the cellulase increased to 1.52 FPU/mL when the strain was mutagenized by UV and DES. Cellulase with high activities was secreted to hydrolysis the steam-pretreated Lespedeza. Glucose yields with the enzymes produced from steam-pretreated Lespedeza, filter paper, microcrystalline cellulose or carboxymethyl cellulose by Trichoderma viride were 17.22%,10.63%,9.55% and 10.27% towards steam-pretreated Lespedeza, respectively. Results indicated that the cellulase from steam-pretreated Lespedeza medium possessed the highest cellulase activities and it was the most efficient cellulase for hydrolysis of steam-pretreated Lespedeza. The degree of polymerization, crystallinity index and photos scanned by the scanning electron microscopy of degraded residues were also illustrative for enzymatic effect. Trichoderma viride cellulase performed better hydrolysis capability to lignocelluloses, holocellulose and cellulose of steam-pretreated Lespedeza compared with cellulase from the other 3 strains. Glucose yields of lignocelluloses, holocellulose and cellulose of steam-pretreated Lespedeza were 32.42%,72.27% and 90.09%, respectively. Results of protein concentrations, FPAs andβ-glucosidase activities also indicated that Trichoderma viride cellulase exhibited the most effective synergism and active adsorption-desorption on the substrate, which make it the preferential enzyme to degrade lignocellulosic materials. Invalid adsorption between lignin and cellulase exsited even after the enzyme was released to the digest. Tween 80, Gleditsia Saponin and Tea Saponin could improve activities and synergism in cellulase system. Glucose yields of furfural were increased from 25.85% to 33.62%,34.52% and 54.07% with additions of the 3 surfactants, respectively. Glucose yields of steam-pretreated Lespedeza were increased from 22.14% and 25.59% to 23.63% and 34.41%. Surfactants could improve activities and synergism in cellulase system. The result indicated that native surfactant Gleditsia Saponin and Tea Saponin were better than chemical surfactant Tween 80. The [3-1,4-glucosidic bond of Tea Saponin would be cut off in the hydrolysis process. However, surface tension in the digest of Tea Saponin with Trichoderma viride cellulase was stabilized after 48 h at high enzyme loading. The result demonstrated that Trichoderma viride cellulase would not destroy the functional structure of Tea Saponin. Tea Saponin was suitable to improve hydrolysis of lignocellulose by Trichoderma viride cellulase.Studies of cellulase production by Trichoderma strains, adsorpotion and desorption of cellulase on the substrate, and effect of native surfactant on hydrolysis are significant to industrialize the cellulosic ethanol production.