Expression and characterization of a novel GH128 laminarinase OUC-BsLam26 harboring both hydrolyzing and transferring activities

Laminarin oligosaccharides (LOSs) with a specific degree of polymerization prepared through the laminarin degradation via laminarinase present more significant nutritional functions and application values. Human intestinal bacteria are promising potential producers of novel carbohydrate-active enzymes with unique properties. Here, a novel glycoside hydrolase family 128 (GH128) laminarinase OUC-BsLam26 from the intestinal bacterium Bacteroides sp. CBA7301 was heterologously expressed and characterized. The recombinant OUC-BsLam26 with a molecular mass of 49.86 kDa exhibits highest activity (6.60 U/mg) at 45 ℃ and pH 6.0, which shows noticeable temperature and pH stability. The purified OUC-BsLam26 could degrade laminarin via an endo-type mode with the generation of laminaripentaose, laminaritetraose, laminaritriose, and laminaribiose, among them, laminaritetraose is the principal product, which accounts for 45.25% of the total products, which is significantly different from the reported GH128 laminarinases. The minimum recognition substrate of OUC-BsLam26 is laminarihexaose. Furthermore, OUC-BsLam26 also could catalyze the transglycosylation process with the production of some novel glycosides. Altogether, the intestinal bacterium Bacteroides sp. CBA7301 contains laminarinase with unique product composition and OUC-BsLam26 is a hopeful bio-catalyst with the potential to produce laminaritetraose and some novel glycosides.