Cloning,expression,characterization,and high cell-density production of recombinant endo-1,4-beta-xylanase from Aspergillus niger in Pichia pastoris

摘要

A recombinant gene XylB(564 bp)encoding endo-1,4-beta-xylanase,obtained from Aspergillus niger BCC14405,was successfully cloned and secreted as a 21 kDa in Pichia pastoris under the control of AOX1 promoter.The activity of the recombinant xylanase was highest at 55 °C which was 5 °C higher than native xylanase.In addition,the recombinant xylanase was active over the range of pH 3.6-6.5 with maximal activity at pH 5(8007 U/mg).When compared to a commercial enzyme,in vitro digestibility of the recombinant enzyme was 1.8- and 2.4-folds higher digesting rates of rice bran and soybean meal fibers,respectively.Two-liter production of xylanase was performed with BSM medium which increased cell concentration up to 84.5 g_(dry-weight)/L via the 80% mu_(max)exponential feed strategy.This process provided maximum xylanase production(3676 U/mL)with highest specific activity(7352U/mgp_(rotein))and volumetric productivity(22,832 U/L/h)at 3.0%(v/v)methanol induction.By far,this was the highest xylanase expression in P.pastoris host system being reported.Thus,this BCC14405 recombinant xylanase could be produced and used effectively as a feed additive for animals.