Characterization and efficient production of an α-agarase from marine bacterium Catenovulum maritimum STB14

Agarases are enzymes that degrade agar and agarose to produce agar oligosaccharides with multiple functional activities. Compared with β-agarases, the natural source of α-agarases is limited, which severely restricts the industrial application of α-agarases. Here, we cloned and heterologously expressed an α-agarase belonging to glycoside hydrolase family 96 named Cm-AGA from the marine bacterium Catenovulum maritimum STB14. The production conditions of recombinant Cm-AGA were optimized as: taking Terrific Broth (TB) (pH 6.5) with 5 g/L of fructose and 24 g/L of yeast extract H07014 as the fermentation medium, after culturing at 37°C for 2 h, isopropyl-β- d-thiogalactoside was added with a final concentration of 0.01 mM to induce for 44 h. The obtained enzyme activity was 13.81 U/ml and was about 6.6 times the initial activity. The specific activity of recombinant Cm-AGA was 206.1 U/mg, the optimum temperature and pH were 35°C and 8.0, respectively, and the enzyme activity could be activated by Mn²⁺ and Ca²⁺. The hydrolysis product results showed that Cm-AGA is the first reported α-agarase with agarobiose (A2) and agarotetraose (A4) as the dominant products, suggesting the great potential of Cm-AGA in the efficient production of agaro-oligosaccharides with a low degree of polymerization.