Cloning and heterologous expression of cellulose free thermostable xylanase from Bacillus brevis

Xylanase gene isolated from Bacillus brevis was expressed in E. coli BL21. Sequencing of the gene (Gen Bank accession number: HQ179986) showed that it belongs to family 11 xylanases. The recombinant xylanase was predominantly secreted to culture medium and showed mesophilic nature (optimum activity at 55 degrees C and pH 7.0). The cell free culture medium exhibited 30 IU/ml xylanse activity. The enzyme did not show any cellulose activity and was active under wide range of temperature (40 degrees C to 80 degrees C) and pH (4 to 9). The enzyme showed considerable thermo stability and regained over 90% of activity, when returned to 55 degrees C after boiling for 5 min. These physiochemical properties of B. brevis xylanse show high potential of its applications in paper and pulp industry.