Production of a thermostable 1,3-1,4-β-glucanase mutant in Bacillus subtilis WB600 at a high fermentation capacity and its potential application in the brewing industry

Abstract

1,3-1,4-β-glucanase was an important biotechnological aid in the brewing industry. In a previous research, a Bacillus BglTO mutant (BglTO) with high tolerance towards high temperature and low-pH conditions was constructed and expressed in Escherichia coli. However, E. coli was not a suitable host for enzyme production in food industry. Therefore, the present work aimed to achieve the high-level expression of BglTO in Bacillus subtilis WB600 and to test its effect in Congress mashing. The β-glucanase mutant was successfully expressed in B. subtilis WB600 and favorable plasmid segregation and structural stability were observed. The maximal extracellular activity of β-glucanase in recombinant B. subtilis WB600 reached 4840.4UmL^-1 after cultivation condition optimization, which was 1.94-fold higher than that before optimization. The fermentation capacity of recombinant B. subtilis reached 242.02UmL^-1h^-1, which was the highest among all reported β-glucanases. The addition of BglTO in Congress mashing significantly reduced the filtration time and viscosity of mash by 29.7% and 12.3%, respectively, which was superior to two commercial enzymes. These favorable properties indicated that B. subtilis WB600 was a suitable host for production of BglTO, which was promising for application in the brewing industry.

Keywords: 1,3-1,4-β-glucanase; Bacillus subtilis WB600; Congress mashing.