Display of fungi xylanase on Escherichia coli cell surface and use of the enzyme in xylan biodegradation.

The cell surface display technique allows expression of target proteins or peptides on microbial cell surface by fusing an appropriate protein as an anchoring motif. Herein, we constructed an Escherichia coli-based whole-cell biocatalyst displaying Thermomyces lanuginosus DSM 5826 xylanase (XynA) on the cell surface and endowed the E. coli cells with the ability to degrade xylan. The XynA was fused in frame to the C-terminus of Lpp-OmpA fusion previously shown to direct various other heterologous proteins to E. coli cell surface. The expressed Lpp-OmpA-XynA fusion protein has a molecular weight of approximately 37 kDa, which was confirmed by SDS-PAGE and Western blot analysis. The enzyme activity of the surface-displayed xylanase showed clear halo around the colony. The XynA-displaying E. coli-based whole-cell biocatalyst xylanase activity was mainly detected with whole cells by determination of activity. The XynA-displaying E. coli-based whole-cell biocatalyst showed highest XynA activity at pH 6.2 and 65 °C, respectively. These results suggest that E. coli, which displayed the xylanase on its surface, could be used as a whole-cell biocatalyst in xylooligosaccharide production.