Laminarin oligosaccharides (LOSs) degraded from laminarin present nutritional functions. Laminarinases with high activity and good stability are significant tools for LOS production. OUC-SaLam66, a novel GH128 laminarinase from Streptomyces albus, was heterologously expressed. OUC-SaLam66 harbored a significant activity advantage up to 2294.80 U/mg at 45 °C and pH 4.0; meanwhile, it could preserve 80% activity at 45 °C for 12 h, indicating good stability. Significantly, its residual activity was over 75% after incubating at 100 °C for 1 h. Differential scanning calorimetry and molecular dynamic modeling revealed that its melting point and RMSD average point were 114.83 °C and 0.125 nm at 100 °C, respectively, which further proved its superior stability. Its apparent Km and Vmax against laminarin were 6.437 mM and 2.5 μg/min/mg, respectively. Hydrolysis products were mainly composed of laminaritriose and laminaribiose. The high activity and thermostability of OUC-SaLam66 make it a promising candidate for LOS preparation.
Keywords: expression; hydrolytic activity; laminarin oligosaccharides; laminarinase; thermostability.