Screening Of Xylanase Producing Strains, Optimization Of Fermentation And Studies On Enzymatic Property

In this paper,105 strains of xylan degradation bacteria that can formation transparent hydrolysis circle on select media were isolated from soil samples and strains of preserved in laboratory. According to the xylanase activity and hydrolysates after shaking flask fermentation, Trichoderma koningii 368 with the solid-state fermentation enzyme activity of 8.506 IU/g was selected, it could hydrolyze xylan into xylose and xylooligosaccharides (contains 2-5 xylose molecules).The solid-state fermentation conditions for xylanase of Trichoderma koningii was optimized by single factor experiment and orthogonal experiment. The optimization conditions are as follows:the bran and corn cob are mixed at ratio 2:8 as carbon source, (NH4)2SO42.5%, MnSO40.50%, the ratio of material to water is 1:1.5(w/w), the initial pH save the state of nature, the culture temperature is 30?, the fermentation time is 6 day. At the optimal solid-state fermentation conditions, the activity of xylanase was up to 11.98IU/g.Xylanase activity increased 11.31-12.28 times through ammonium sulfate precipitation, dialysis and concentration. The native-PAGE showed that the enzyme liquid of Trichoderma koningii with solid-state fermentation have 15 kinds of protein. The xylanase A (Xyn-A) was separated and purified by protein recovery, concentration and measuring xylanase. The relative molecular mass was 22.80 ku and isoelectric point was 6.45 of the Xyn-A through SDS-PAGE and isoelectric focusing electrophoresis.The enzymatic properties were studied, the optimum pH was 6.0, and xylanase was stable in the range pH 5.0-8.0, the relative enzyme activity maintained above 84%. The optimum temperature was 50?, and xylanase was stable below 50?, the relative residual enzyme activity maintained above 91%. While the enzyme activity loss quickly above 50?. The promoting effect of metal ions on the activity of xylanase is no significant, the activity of xylanase can be increased by 2% and 9% in 1 mmol/L K+ and Ca2+ respectively, Na+ almost has no influence on xylanase, but Cu2+, Al3+ and Mg2+ inhibited the activity. Studied on hydrolysates that xylanase of Trichoderma koningii to xylan and corn cob adopting thin layer chromatography, the main hydroly sates of xylan (1% standard sample) were xylose and xylooligosaccharides (contains 2-5 xylose molecules), while the main hydrolysates of corn cob were xylooligosaccharides.