The Study On Chemical Modification Of Xylanase

The G/11 xylanase expressed by the Picha pastor is GS115 was purified and modified with different chemical reagents to enhance its thermal stability. The various stabilizing agents were also used to protect the xylanase.The results of the research are as follows:(1) Preparation of the xylanase from Picha pastoris:we succeeded to purify the xylanase of Picha pastoris by fermentation, centrifugation, deposition with 65% (NH4)2SO4, dialysis and concentration.(2) Chemical modification of xylanase:the xylanase was modified with chitosan, pectin, dextran and diamino-PEG separately. The results indicated that the thermostability of the xylanase modified with diamino-PEG was improved and the molecular weight of modified enzyme was changed to a wide range.(3)Optimization of the modification condifition of the xylanase with diamino-PEG: the added quantities of diamino-PEG and coupling agent of EDAC/NHS in modified reaction were optimized. The mol rate of xylanase/ diamino-PEG/ EDAC/NHS was 1/1000/100.The relative residual activity of modified xylanase by this condition was 61.6% after incubated 10min at 55℃,over 29.1% than unmodified xylanase.The relative residual activity of modified xylanase by this condition was 30% after incubated 5min at 60℃,and the unmodified xylanase had no activity. The xylanase after modification reaction retained more than 60% of its initial activity.(4) Enzymological characteristics of modified xylanase:we determined the optimum temperature, pH, pH stability, thermostability, substrate specificity, hydrolysate components of modified and unmodified xylanase. Only the pH stability and thermostability was changed.(5)Effect of stabilizing agent on thermostability:the thermostability of xylanase was determined after the enzyme was incubated with 1% dextran,1% pectin,0.2M trehalose,0.2M sucrose,0.2M mannitol,0.5% glycerin and 0.2% sodium benzoate, separately, at 55℃for 15-30 min. The results showed that the trehalose, sucrose and mannitol observably improved the thermostability of xylanase, and the dextran and glycerin had no effect on the thermostability of xylanase, while the pectin and sodium benzoate reduced the thermostability of xylanase.