Characterization of a thermostable xylanase from an alkaliphilic Bacillus sp.

A xylanase gene (xyn10) from alkaliphilic Bacillus sp. N16-5 was cloned and expressed in Pichia pastoris. The deduced amino acid sequence has 85% identity with xylanase xyn10A from B. halodurans and contains two potential N-glycosylation sites. The glycosylated Xyn10 with MW 48 kDa can hydrolyze birchwood and oatspelt xylan. The enzyme had optimum activity at pH 7 and 70 degrees C, with the specific activity of 92.5U/mg. The Xyn10 retained over 90% residual activity at 60 degrees C for 30 min but lost all activity at 80 degrees C over 15 min. Most tested ions showed no or slight inhibition effects on enzyme activity.