Cloning and Characterization of a PL6 Alginate Lyase Aly94 from the Marine Bacteria

Microbial alginate lyases are essential biocatalysts for analyzing alginate structure and sustainably producing bioactive alginate oligosaccharides (AOS). In this study, we characterized Aly94, a novel alginate lyase from the polysaccharide lyase family 6 (PL6) family, identified from a marine sediment metagenomic library. Biochemical analyses showed Aly94 exhibits optimal activity at 40 ℃ in 50 mM NaH₂PO₄-Na₂HPO₄ buffer (pH 7.0). Adding 20 mM NaCl significantly increases its catalytic efficiency. The enzyme exhibits a strong preference for polyguluronate (polyG) over polymannuronate (polyM), with specific activities of 4.19 U/mg (polyG), 0.25 U/mg (polyM), and 2.45 U/mg (alginate). When degrading substrates-particularly polyG-Aly94 primarily generates trisaccharides. Although Aly94 acts as an endolytic alginate lyase, it also could digest the monosaccharides from small oligosaccharide chains (∆G3, ∆G4). These catalytic properties, combined with its polyG-specific depolymerization, made Aly94 a promising candidate for biotechnological applications requiring controlled alginate saccharification and high-value AOS production.