Optimization of the Trichoderma reesei endo-1,4-beta-xylanase production by recombinant Pichia pastoris

Abstract

In this study, an optimization of xylanase expression by recombinant Pichia pastoris was carried out with a 2 3 factorial design. The influence of initial cell density, methanol and yeast nitrogen base concentration was evaluated, and the cell density was found to be the most important parameter. Considering with the yield of enzyme activity and the amount of methanol and YNB used for fermentation, the optimal conditions in this study for enzyme production were 0.5% (w/v) methanol, 0.8% (w/v) YNB, and initial cell density of 3 × 10 8 cells/ml. The enzyme production in 15-l fermenter with the optimized conditions was performed and a twofold higher xylanase activity was obtained. The produced enzyme was practically free of cellulolytic activity. The molecular mass (21 kDa), optimal pH (6.0) and substrate specificity of the enzyme were both identical to native enzyme. However, the thermostability of the recombinant enzyme was better than the native enzyme. The optimal temperature for the recombinant Xyn2 was 5 °C higher than native Xyn2, and remained at least 90% of its activity after 30 min incubation at 55 °C. The high level of fully active recombinant xylanase obtained in P. pastoris makes this expression system attractive for fermenter growth and industrial applications.