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

Aims: 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 37·5-kDa protein encoded by gene xylM1989, was found in the soluble fractions. The resulting protein, denoted XylM1989, showed β-xylosidase and α-arabinosidase activities. It fell in the GH43 family and resembled a Sphingobacterium sp. protein. The XylM1989 showed optimum activity at 20°C and pH 8·0. Interestingly, it kept approximately 80% of its β-xylosidase activity in the presence of 0·5% (w/v) furfural and 0·1% (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.
(© 2017 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of Society for Applied Microbiology.)