[Isolation and characterization of an alkaline xylanasefrom a newly isolated Bacillus sp. QH14]

Twenty-fivealkaline xylanase producing strains were isolated from Qinghai Lake side soil samples. Among these strains, QH14 produced 648.79 U/mLxylanase, and the enzymatic specific activity was 1148.56 U/mg after purification. This alkaline xylanase producing strain belongs to genus Bacillus based on16S rDNA sequencing analysis and then was designated as Bacillus sp. QH14. The alkalinexylanaseencoding gene, XynQH14, was cloned from Bacillus sp. QH14 and expressed in Escherichiacoli BL21 (DE3). The specific activity of the recombinant xylanase XynQH14 was 700.47 Umg-1 after purification by Ni-NTA affinity chromatography. The optimal temperature and pH of XynQH14 were 60℃ and pH9.2, respectively. Its activity was 50% of initial activity after incubation at 55 ℃ for 1h, 80% at pH7-11 at 37 ℃ for 24 h, and 31.02% at pH11 at 50℃ after 24 h, indicating that XynQH14 isthermostable and alkali-stable. These properties ofXynQH14 suggest its favorable potential applications in pulp and paper industries.