Screening Of Corncob Residue Degrading Fungi And The Studies On Enzyme Fermentation And Characters

Corncob residue is the waste of xylose manufacture from the dilute acid hydrolysis of corncob. It’s composed of48.5%cellulose,21.3%lignin and23.5%hemicellulose.In this study,48strains which could use corncob residue as only carbon source were found by primary screening of enrichment culture, purifying and identifying of Congo red cellulose medium. By secondary, screening of liquid fermentation, a cellulose-production fungus, Trichoderma C1, which can achieve high enzymatic hydrolytic efficiency to corncob residue, was isolated.In order to improve the efficiency of enzymatic hydrolysis of corncob reside, optimal cellulase production with C1strain was carried out. As the results, the best culture medium contains NaCl0.02%, KH2PO40.3%, MgSO40.06%, CaCl20.03%, FeCl30.001%,(NH4)2SO40.1%, NaNO30.1%, Corn steep liquor4%, peptone0.1%, corncob residue2%, wheat bran1.5%, rice straw0.5%, corncob0.5%. Cellulase was produced by the strain incubated under the condition of28℃,180rpm for4days. The liquid medium volume was50mL/250mL, the quantity of inoculation was10%, and the initial pH of culture medium was4.0. Under these conditions, the enzyme activity of corncob residue could reach55.6U/mL.The optimal conditions of hydrolysis were55℃and pH4.0. Under this condition, glucose could reach2.3%after corncob residues were hydrolyzed for48h on the10%corncob residues base. Within a certain concentration, Tween-80and polyethylene glycol could enhance the cellulase activity greatly, by which glucose could reach over3%after corncob residues were hydrolyzed for24h in the same conditions. Co2+and Mn2+could also enhance the cellulase activity, but were not effective as much as Tween-80and polyethylene glycol.Meanwhile, a method, which used1-phenyl-3-methyl-5-pyrazolone (PMP) as the derivatization agent of carbohydrates, had been established to detect the carbohydrates by capillary electrophoresis. Under the optimized conditions, six reducing sugar derivatives were well separated. The sugars gained in the hydrolysate consist of glucose4.1%and xylose0.4%after enzymolysis for72h on the10%corncob residues base, determined by capillary electrophoresis.