Thermostability and Xylan-Hydrolyzing Property of Endoxylanase Expressed in Yeast Saccharomyces cerevisiae

Abstract

The endoxylanase gene (xynB, GeneBank access code U51675), including its signal sequence, from Bacillus spp. was amplified and connected in frame downstream of yeast ADH1 promoter and then the resulting plasmid, pAEDX-1, was introduced into Saccharomyces cerevisiae. When the yeast transformants were grown on YPD medium, the majority of endoxylanase activity was detected in the extracellular culture medium, indicating that the signal peptide of Bacillus endoxylanase functioned well in yeast. In the batch cultivation of yeast transformants, the total expression level of endoxylanase and secretion efficiency were measured to be about 9.8 U/mL and 66.2%, respectively. The extracellular endoxylanase expressed in yeast showed an enhanced thermal stability due to the N-linked glycosylation. Through the hydrolysis of birchwood xylan with the endoxylanase, it was found that xylobiose and xylotriose were produced as major products with equimolar ratio.