Optimization of fermentation conditions of marine algicidal bacterium Microbulbifer sp. BS03 by uniform design

The optimal parameters of fermentation conditions of marine bacterium Microbulbifer sp. BS03 producing algicidal substances against Alexandrium tamarense were obtained by using Uniform Design and quadric polynomial regression methods. Five main factors were achieved through single factor experiments, that is, carbon source, nitrogen source, pH, incubation time and inoculum size. The U15 (155) design result showed the optimum conditions of experiment were as follows: sugar 8 g/L, peptone 10.5 g/L, initial pH 7.5, incubation time 32 h, and inoculum size of 3.00%. According to the verification experiment, under the optimal conditions, the dry biomass was 4.725 g/L which was increased by 31.35% and LD50 was 0.768% which was decreased by 25.14% compared with those of the basic fermentation conditions. This outcome will help us to separate active substances from complex components in medium and thus to reveal the mechanism of algicidal activity in the future.