Prospects for Bio-Industrial Application of an Extremely Alkaline Mannanase From Bacillus subtilis subsp. inaquosorum CSB31

Mannan-degrading enzymes are attracting growing interest in bio-industrial applications, such as the pulp and paper, food, and pharmaceutical industries. In this study, an extremely alkaline mannanase (MnB31) was produced by Bacillus subtilis subsp. inaquosorum CSB31. MnB31 was purified to 17.92-fold with a 21.51% yield and specific activity of 1,796.13 Umg−1 by anion-exchange and gel filtration column chromatography. The biochemical characterization of MnB31 was performed, and the results were as follows: molecular weight of ~47 kDa with an optimum temperature of 60°C and pH of 12.5. The enzyme was strongly activated by Co2+, Mn2+, Na+, and K+, and inhibited by Zn2+, Ni2+, and Mg2+. Halo-tolerance (10% NaCl), urea stability (3 M), and protease resistance were also observed. The kinetic parameters of MnB31 were found to be Km of 0.043 mgml-1, and Vmax of 1,046≥3.605 Umg-1, respectively. In addition, the thermodynamical parameters were investigated; the activation energy (Ea) was found to be 31.36 kJmol-1 with a Kcat value of 156.9×104 sec-1, ΔH (28.59 kJmol-1), ΔG (42.38 kJmol-1), ΔS (-41.39 Jmol-1K-1), Q10 (1.40), ΔGE-S (-8.697 kJmol-1), and ΔGE-T (-48.22 kJmol-1). These results suggest that MnB31 has potential bio-industrial application, due to its greater hydrolytic efficiency and feasibility of enzymatic reaction.