Optimized Production Of Xylanase By Recombinant Pichia Pastoris And Effects Of The Enzyme On Performance Of Growing Pigs

The present study was conducted to optimize the fermentation medium for xylanase production by recombinant Pichia pastoris developed in our laboratory. The enzymatic properties of the recombinant xylanase and its effects on performance and fecal bacterial flora in growing pigs were both evaluated.Exp.l Optimized production of xylanase by recombinant pichia pastoris and the enzymatic properties of the enzymeA recombinant pichia pastoris PX-1previously developed in our laboratory exhibited its great potential for large scale xylanase production. In order to further improve the production level and reduce the production cost, the fermentation medium for PX-1was optimized in Exp.1. The results showed that the incubation time reduced4h using glucose to replace glycerol in traditional industrial culture medium. However, the cell density in growth period and the production level of xylanase in induction period were declined. Through changing the ingredients in glycerol basal medium, the cell density increased to1.2fold at the same fermentation conditions. The yield of xylanase in the optimized medium was similar to traditional glycerol medium, but the induction time was decreased, resulting in reduction of the production costs. Analysis of the enzymatic properties demonstrated that the optimum pH was5.5and the optimum temperature was55℃. The xylanase was stable at50℃, but was inactivated after30min incubation at70℃. Moreover, the type and concentration of metal ions significantly affected the activity of the recombinant xylanase.Exp.2Effects of xylanase supplementation into wheat-based diet on growth performance and fecal microorganism in growing pigsTo determine the effects of the recombinant xylanase on performance, nutrient digestibility and fecal bacterial flora in growing pigs fed with wheat-based diet, eighty healthy DLY crossbred pigs of initial mean BW of40kg were randomly assigned to5 dietary treatments with4pigs per pen and4pens per diet for a28-d feeding period.The diets were:corn-based diet (positive control);wheat-based diet (negative control); wheat-based diet supplemented with different levels of xylanase (500,1000and2000U/kg). Results showed that xylanase supplementation to wheat-based diet increased the ADG (P<0.01), ADFI (P<0.05) and digestibilities of nutrients (P<0.05). The positive effects were dose-dependent and the best results were obtained at2000U/kg. Moreover, xylanase supplementation significantly increased serum glucose, xylose and thyroid hormone (T3, T4) concentrations while reduced the BUN concentration (P<0.05). Interestingly, the microbial flora of the digestive tract was affected by dietary compositions and xylanase supplementation. Xylanase supplementation could maintain the microfloral balance for pig gastrointestines. It is concluded that the recombinant xylanase developed in our laboratory has significant efficacy to improve the production performance and nutrient utilizations of pigs fed wheat-based diet.In conclusion, the optimal medium for PX-1producing recombinant xylanase was GLY-LS-BSM, the optimal pH and temperature for the xylanase were5.5and55℃respectively. Xylanase supplementation to wheat-based diet could improve the performance and nutrient digestibilities, and maintain the gastrointestinal microfloral balance for pigs, the recommended supplemental dose was2000U/kg.