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 ten hemicellulolytic enzymes obtained from a wheat straw-degrading microbial consortium.

METHODS AND RESULTS: Based on previous metagenomics analyses, ten 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(-1) ) furfural and 0.1% (w v(-1) ) 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. This article is protected by copyright. All rights reserved.