Research On Corn Stalk Pretreatment By Ligninolytic Enzymes

The experiment applied ligninolytic enzymes produced by white-rot fungi(Phanerochaete Chrysosporium and CoriolusVersicolor) through fermentation to pre-treat corn stalk. The effect of glucoamylase (cellulase and xylanase) is inhibited by ligninolytic enzymes was discovered. The effect of cellulase is inhibited by ligninolytic enzymes was preliminarily proved with the experiment of Novozymes laccase, in the mean time, the result that lignin is destroyed and the structure of fibre is changed by Novozymes laccase was concluded, the result also shows its promotion of saccharification.Small particles washing process was designed after the proof that ligninolytic enzymes have a direct inhibiting effect on glucoamylase. The process eliminated the effect that fermentation broth and Novozymes laccase directly inhibit glucoamylase, therefore, the rate of sugar yield increased by 19.9% and 9.5%, respectively. Later, the experiment of improving the effect of pretreatment was carried on by changing the different conditions of biological pretreatment. The result indicated that the destroy of lignin and the change of the structure of fibre can promote the enzymatic hydrolysis in the process of glucoamylase. The contributing ability of biological pretreatment to saccharification was concluded by the increase of the rate of sugar yield, the maximum increasing rate of sugar yield is 23.1%.Finally, three tests are designed to analyze the changes of the nature of fibre after the process of pretreatment. Firstly, the change of crystallinity of corn stalk were compared before and after the pretreatment through X-ray diffraction. Secondly, the toxic substances in the pretreatment of acidic and biological methods were compared through HPLC. Thirdly, the change of the fibre of corn stalk were compared before and after the pretreatment through Scanning Electron Microscope. The change of the structural nature of corn stalk with the pretreatment of ligninolytic enzymes was analyzed based on the above aspects, the relations between the change after the pretreatment and the effect of glucoamylase were explained.