Mg2+-induced stabilization of [beta]-galactosidase from Bacillus megaterium and its application in the galactosylation of natural products

Objective To improve the stability of [beta]-galactosidase from Bacillus megaterium YZ08 (BMG) in aqueous hydrophilic solvents and promote its application in the galactosylation of natural products. Results The addition of 5 mM Mg2+ significantly enhanced the stability of BMG in aqueous hydrophilic solvents, and the half-lives of BMG in these solutions reached 56 min to 208 h, while they were only 7 min to 5.9 h without addition of Mg2+. Studies on the kinetic parameters in buffer solution and 30% dimethyl sulfoxide (DMSO) indicated that the affinity of BMG to 2-nitrophenyl-[beta]-d-galactopyranoside and its catalytic efficiency ([kappa] cat/K m) increased with the addition of Mg2+. Furthermore, the addition of Mg2+ facilitated galactosylation reactions in 30% DMSO and increased product conversions by 24-41% due to the reversal of the thermodynamic equilibrium of hydrolysis. Conclusion A convenient approach was established to improve the stability of BMG in aqueous hydrophilic solvents.