Optimization of ultrasonic-assisted enzymatic extraction of polysaccharides from thick-shell mussel (Mytilus coruscus) and their antioxidant activities.

This study aimed to obtain the purified fractions of Mytilus coruscus polysaccharides (MCPs) and investigate their antioxidant activities. MCPs were prepared through ultrasonic-assisted enzymatic extraction optimized by employing the response surface methodology. A single-factor experiment was conducted using the Box-Behnken design to determine the optimum extraction conditions of MCPs. The ultrasonic power was 60 W, liquid-to-material ratio was 30 mL/g, extraction time was 36 min, extraction temperature was 64 °C, enzyme concentration was 3.2%, and polysaccharide extraction yield was 12.86% ± 0.12%. A novel polysaccharide (MCP1-2) was obtained after the purification with AB-8 macroporous resin, DEAE Sepharose Fast Flow, and Sepharose CL-6B column. The molecular weight of MCP1-2 was estimated to be 134.9 kDa according to high-performance gel permeation chromatography. High-pressure liquid-phase chromatography results showed that MCP1-2 contained mannose, rhamnose, glucuronic acid, glucose, galactose, and L-Fuc at a molar ratio of 1.53:1:4.83:81.82:2.36:1.51. Infrared and NMR spectroscopies confirmed that MCP1-2 possessed α- and β- configurations. The antioxidant activities of MCP1-2 were investigated in vitro, and the results showed that MCP1-2 had good antioxidant activity and can be used as a natural antioxidant in food.