Elucidation of\nDomain Function of a Novel Multifunctional\nGlycoside Hydrolase and Its Use in Efficient Preparation of Oligosaccharides\nfrom Kelp Powder

Kelp\ncontained laminarin, cellulose, and alginate as\nmajor polysaccharides\nand could be utilized as functional oligosaccharides. A new multifunctional\nglycoside hydrolase CelA was identified and characterized for the\nefficient degradation of kelp powder. It displayed cellulase (2308.38\nU/mg), alginate lyase (578.68 U/mg), and laminarinase (720.97 U/mg)\nactivities. It exhibited maximal activity on both sodium alginate\nand laminarin at 50 °C and pH 8.0, while it could degrade sodium\ncarboxymethylcellulose (CMC-Na) by maximal activity at 40 °C\nand pH 7.0. The action mode analysis by thin layer chromatography\nand electrospray ionization mass spectrometry indicated that CelA\nadopted an endolytic manner to degrade CMC-Na, sodium alginate, and\nlaminarin releasing oligosaccharides with degrees of polymerization\n(Dps) of 2–5. According to domain analysis, CelA contained\na GH5 module and a PL6 module, and both of them exhibited glycoside\nhydrolase and polysaccharide lyase activity. The docking results revealed\nthat Glu<sub>163</sub> and Glu<sub>250</sub> are essential in cellulose\nand laminarin degradation. As to the degradation of alginate, Asn<sub>376</sub>, Lys<sub>436</sub>, Arg<sub>464</sub>, Asp<sub>496</sub>, and Asn<sub>551</sub> could bind alginate and Tyr<sub>492</sub> and Lys<sub>529</sub> acted as catalytic sites. CelA displayed high\nhydrolysis efficiency for cellulose, β-glucan, laminarin, alginate,\nand kelp powder. Thus, it has strong potential in food and feed industries\nas a catalyst for bioconversion of algal biomass into value-added\nproducts oligosaccharides.