| Corn stalk is an important renewable energy source, and is mainly composed of lignin, cellulose and hemicelluloses. Lignin is conected with semi-cellulose to form a lay of lignin sheath around cellulose by by covalent bonds. The lignin sheath hinders the cellulose molecules in the straw from the contacet with cellulase. Therefore, the key to the development and utilization of straw is how to degrade lignin in the straw at a low cost and in a relatively short period of time.(1) The single factor experiment and response surface design were applied to obtain the optimum medium composition for lignin peroxidase production by Aspergillus oryzae. The optimal medium is composed of(g/L): 30 corn stalk, 4.6 glucose, 1.2 sodium nitrate, 1 corn syrup, 1.2 yeast extract, 0.15 VB1. Under these conditions, the highest lignin peroxidase activity reached 652.34 U/L.(2) To evaluate the ability that H2O2 degrade liginin of corn stalk were increased by single factor experiment and response surface experimental design optimization and the sugar yield was used as index. After optimization, the optimal conditions were obtained: 20 g corn straw after pretreated by 113 oC for 11 min, 50 mL crude enzyme solution, 80 mL 1.5% H2O2 was added to reaction resolution at the flow rate of 0.4 mL/min, 240 m L water(water: material 12:1). After the hydrolysis was carried out for 8 h at 39 oC, the largest sugar yield rate reached to 46.28%.(3) The lignin peroxidase with 18.2 KDa MW was obtained through repeatedly isolation and purify with DEAE cellulose DE-52 ion chromatography and membrane filtration. After the double reciprocal plots with reaction rate vs substrate concentration was drawed, the Km and μmax of the lignin’s degradation reaction by H2O2 using lignin peroxidase as catalyer.The results showed that Km and μmax is parallel. Thus, temperature and pH increase the enzymatic reaction rate by increasing the affinity of the enzyme and the substrate. |
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