Cloning of xynB Gene Encoding Xylanase B from Aspergillus niger and Expression in Sacharomyces cerevisiae

The xylanase xynB gene from Aspergillus niger was cloned and its introns were trimmed off by overlap extension PCR.An expression vector was successfully constructed by ligating the xynB with vector pYES2 and transformed into Saccharomyces cerevisiae INVSC1 using Lithium Acetate method.The signal peptide of xylanase B was replaced with α signal peptide to identify the effect of signal peptide on the secretion of expressed protein,recombinant S.cerevisiae pYES2-xynB with xylanase B original signal peptide and pYES2-xynB-α with α-signal peptide were obtained.The result showed that the xylanase B was expressed successfully.A target protein band of approximately 24kDa was identified on SDS-PAGE gel map.The optimal action temperature of expressed xylanase B was 50℃ and the optimal action pH value was 5.0,Mn2+inhibited the activity of xylanass B strongly.The induction time of maximum activity of xylanase B decreased from 72h to 48h by replacing the xylanse B original signal peptide with α-signal peptide.However,the replacement of signal peptide caused the decrease of the maximum activity of xylanas B from 7.59U to 3.97U.