Construction of whole-cell biocatalyst for xylan degradation through cell-surface xylanase display in Saccharomyces cerevisiae

We constructed a yeast-based whole-cell biocatalyst displaying Trichoderma reesei xylanase H (XYNII) on the cell-surface and endowed the yeast-cells with the ability to degrade xylan. The fusion gene encoding the mature region of XYNII and the C-terminal half (320 amino acid residues from the C-terminal end) of yeast alpha-agglutinin (XYNII-alpha-agglutinin) was constructed and expressed in Saccharomyces cerevisiae under the control of a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter. The expression system of fusion gene encoding XYNII-alpha-agglutinin tagged with RGSHis6 consisting of arginine, glycine, serine, and histidine hexamer (RGSHis6-XYNII-alpha-agglutinin) was also constructed. Immunofluorescence labeling to confirm cell-surface display of the RGSHis6-XYNII-alpha-agglutinin fusion protein, and confirmation of similar xylanase activity in yeast-cells expressing XYNU-alpha-agglutinin and RGSHis6-XYNII-alpha-agglutinin but not in the culture medium, indicated that XYNII was displayed on the cell-surface in the active form. The XYNII-displaying yeast-based whole-cell biocatalyst showed highest XYNII activity at pH 5.0 and 40 degreesC, respectively. This whole-cell biocatalyst is expected to find application not only in the first step of fermentation of xylan to ethanol but also in xylooligosaccharide production. (C) 2002 Elsevier Science B.V. All rights reserved.