Enhanced Solvent-Stable Alpha Glycosidase Production by Bacillus licheniformis JXC-1 by Optimization of Feeding Strategies

In the previous work, we screened a strain (Bacillus licheniformis JXC-1) producing solvent-stable (10 % N, N-Dimethylformamide, short for DMF) alpha-glucosidase from several different soil samples. In this work, we attempt to improve the alpha-glucosidase production by optimization of feeding strategies in a 3-L fermenter. Specifically, the key factors of solvent-tolerant alpha-glycosidase production were investigated first, and the optimal conditions (pH 7.0, the initial maltose concentration 25 g/L, and agitation speed 600 rpm) were obtained; the enzyme activity reached 444.7 U/L under the optimal conditions. Then, four feeding strategies with different feeding rates for 4-8 h to feed maltose or both maltose and tryptone were carried out, and it was found that feeding maltose and tryptone at a rate of 2.25 mL/h (4-5 h), 6.75 mL/h (5-6 h), 9 mL/h (6-7 h), and 15 mL/h (7-8 h) significantly increased the alpha-glycosidase production, from 444.7 to 872.5 U/L.