Expression and characterization of a bifunctional glycoside hydrolase IDSGH5-23 from Ruminococcus albus

Glycoside hydrolases such as glucanase and xylanase are important components of enzyme preparations that can hydrolyze and ablate non-starch polysaccharide antinutritional factors in feed. According to the metatranscriptomic data obtained previously from rumen microbiota in Hu sheep, a novel bifunctional glucanase/xylanase gene, IDSGH5-23, was cloned from cDNA of rumen microbiota. The gene was heterologously expressed in Escherichia coli, and the recombinant enzyme was functionally characterized. The results showed that the theoretical molecular weight and isoelectric point of IDSGH5-23 were 45.8 kDa and 4.44, exhibiting 99.51% similarity to amino acid sequence of GH5 protein (GenBank accession number: WP_013499238.1) from Ruminococcus albus. The IDSGH5-23 had the optimum temperature of 30 ℃ and the optimum pH of 6.0, and remained stable ranging of pH 4.0-7.0. Moreover, the IDSGH5-23 was robust in catalyzing barley β-glucan, lichenan, konjac gum and beechwood xylan. The enzyme IDSGH5-23 mainly released cellotriose from lichenan or cellooligosaccharides with a degree of polymerization beyond 3 from barley β-glucan. Besides, the enzyme IDSGH5-23 was capable of generating xylotriose, xylotetraose, xylopentaose and xylohexaose from beechwood xylan. In summary, a bifunctional glucanase/xylanase protein derived from rumen microbes, IDSGH5-23, is obtained and characterized in this study, laying a foundation for feed enzyme development and oligosaccharides preparation.