Production of cellulase‐free xylanase by the recombinant Bacillus subtilis and its applicability in paper pulp bleaching

A metagenomic xylanase gene (Mxyl) was successfully cloned into shuttle vector pWH1520 and expressed in Bacillus subtilis extracellularly. On induction with xylose, recombinant xylanase secretion commenced after 6 h. Identifying critical variables for recombinant xylanase production by one‐variable‐at‐time approach followed by optimization of the selected variables (xylose, inoculum density, incubation density) by response surface methodology (RSM) led to three‐fold enhancement in extracellular xylanase production (119 U mL^?1). When the pulp was treated with recombinant xylanase at 80°C and pH 9.0, kappa number of the pulp was reduced with concomitant increase in brightness and 24% reduction in chlorine consumption. This is the first report on the expression of metagenomic xylanase gene in Bacillus subtilis extracellularly and its utility in developing an environment‐friendly pulp bleaching process. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1441–1447, 2013