Characterization of a furan aldehyde-tolerant<i>β</i>-xylosidase/<i>α</i>-arabinosidase obtained through a synthetic metagenomics approach

Abstract

The aim of the study was to characterize 10 hemicellulolytic enzymes obtained from a wheat straw-degrading microbial consortium. Methods and Results: Based on previous metagenomics analyses, 10 glycosyl hydrolases were selected, codon-optimized, synthetized, cloned and expressed in Escherichia coli. Nine of the overexpressed recombinant proteins accumulated in cellular inclusion bodies, whereas one, a 375-kDa protein encoded by gene xylM1989, was found in the soluble fractions. The resulting protein, denoted XylM1989, showed b-xylosidase and a-arabinosidase activities. It fell in the GH43 family and resembled a Sphingobacterium sp. protein. The XylM1989 showed optimum activity at 20C and pH 80. Interestingly, it kept approximately 80% of its b-xylosidase activity in the presence of 05% (w/v) furfural and 01% (w/v) 5-hydroxymethylfurfural. Additionally, the presence of Ca 2+ , Mg 2+ and Mn 2+ ions increased the enzymatic activity and conferred complete tolerance to 500 mmol l 1 of xylose. Protein XylM1989 is also able to release sugars from complex polysaccharides. Conclusion: We report the characterization of a novel bifunctional hemicellulolytic enzyme obtained through a targeted synthetic metagenomics approach. Significance and Impact of the Study: The properties of XylM1989 turn this protein into a promising enzyme that could be useful for the efficient saccharification of plant biomass.