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

Mannan-degrading enzymes have been growing interest in bio-industrial applications, such as the pulp and paper, food, and pharmaceutical industries. In this study, an extremely alkaline mannanase (MnB31) is produced by Bacillus subtilis subsp. inaquosorum CSB31. MnB31 is purified to 17.92-fold with a 21.51% yield and specific activity of 1,796.13 U mg⁻¹ by anion-exchange and gel filtration column chromatography. The biochemical characterization of MnB31 is performed, and the results are as follows: molecular weight of ≈47 kDa with an optimum temperature of 60 °C and pH of 12.5. The enzyme is 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 are also observed. The kinetic parameters of MnB31 are found to be K_m of 0.043 mg ml⁻¹, and V_max of 1,046 ± 3.605 U mg⁻¹, respectively. In addition, the thermodynamical parameters are investigated; the activation energy (E_a) is found to be 31.36 kJ mol⁻¹ with a K_cat value of 156.9 × 10⁴ s⁻¹, ΔH (28.59 kJ mol⁻¹), ΔG (42.38 kJ mol⁻¹), ΔS (−41.39 J mol⁻¹ K⁻¹), Q₁₀ (1.40), ΔG_E–S (−8.697 kJ mol⁻¹), and ΔG_E-T (−48.22 kJ mol⁻¹). These results suggest that MnB31 has potential bio-industrial application, due to its greater hydrolytic efficiency and feasibility of enzymatic reaction.