Expression and Characterization of a Novel Thermostable and pH-Stable β-Agarase from Deep-Sea Bacterium Flammeovirga Sp PC4

A novel gene (aga4436), encoding a potential agarase of 456 amino acids, was identified in the genome of deepsea bacterium Flammeovirga sp. OC4. Aga4436 belongs to the glycoside hydrolase 16 beta-agarase family. Aga4436 was expressed in Escherichia coli as a fusion protein and purified. Recombinant Aga4436 showed an optimum agarase activity at 50-55 degrees C and pH 6.5, with a wide active range of temperatures (30-80 degrees C) and pHs (5.0-10.0). Notably, Aga4436 retained more than 90%, 80%, and 35% of its maximum activity after incubation at 30 degrees C, 40 degrees C, and SO degrees C for 144 h, respectively, which exhibited an excellent thermostability in medium-high temperatures. Besides, Aga4436 displayed a remarkable tolerance to acid and alkaline environments, as it retained more than 70% of its maximum activity at a wide range of pHs from 3.0 to 10.0 after incubation in tested pHs for 60 min. These desirable properties of Aga4436 could make Aga4436 attractive in the food and nutraceutical industries.