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 Ca²⁺, Mg²⁺ and Mn²⁺ 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.