Purification and characterization of β-mannanase from Reinekea sp. KIT-YO10 with transglycosylation activity

Marine bacterium Reinekea sp. KIT-YO10 was isolated from the seashore of Kanazawa Port in Japan as a seaweed-degrading bacterium. Homology between KIT-YO10 16S rDNA and the 16S rDNA of Reinekea blandensis and Reinekea marinisedimentorum was 96.4 and 95.4%, respectively. Endo-1,4-β-D-mannanase (β-mannanase, EC 3.2.1.78) from Reinekea sp. KIT-YO10 was purified 29.4-fold to a 21% yield using anion exchange chromatography. The purified enzyme had a molecular mass of 44.3 kDa, as estimated by SDS-PAGE. Furthermore, the purified enzyme displayed high specificity for konjac glucomannan, with no secondary agarase and arginase activity detected. Hydrolysis of konjac glucomannan and locust bean gum yielded oligosaccharides, compatible with an endo mode of substrate depolymerization. The purified enzyme possessed transglycosylation activity when mannooligosaccharides (mannotriose or mannotetraose) were used as substrates. Optimal pH and temperature were determined to be 8.0 and 70 °C, respectively. It showed thermostability at temperatures from 20 to 50 °C and alkaline stability up to pH 10.0. The current enzyme was thermostable and thermophile compared to the β-mannanase of other marine bacteria.