Efficient Production of Bacillus flexus β-amylase in Brevibacillus choshinensis and its Potential as an Industrial Catalyst

β-amylases catalyze the generation of β-maltose from the non-reducing end of starch through hydrolysis of α-1,4-glucosidic bonds. Bacterial β-amylases are more suitable for β-maltose production, but their yields are typically too low. In this study, the β-amylase from Bacillus flexus CCTCC2015368 was efficiently produced in Brevibacillus choshinensis. The purified recombinant β-amylase had a specific activity of 2650 U/mg using soluble starch as the substrate, its optimal temperature and pH were 50°C and 7.0, respectively, and its half-life at 50°C and pH 7.0 was 34 h. When produced in the 3-L fermenter under optimal fermentation conditions, the β-amylase activity in the culture supernatant peaked at 4470 U/mL (1.7 mg/mL). After optimizing the reaction conditions, the highest yield of maltose (86.9%) from 30% (wt/vol) potato starch was obtained by combining the B. flexus β-amylase with isoamylase and maltogenic amylase. This study laid the foundation for the large-scale production and wide application of recombinant the B. flexus β-amylase.