Medium Optimization for Bioflocculant-Producing Bacillus fusiformis

A prior study has found that the bioflocculant produced by Bacillus fusiformis has a flocculation effect. However, the flocculation rate needs further improvement. In order to achieve this, the present study optimizes the culture medium compositions for bioflocculant-producing Bacillus fusiformis. The carbon and nitrogen sources were optimized through a single-factor experiment. Subsequently, single-factor, composite, and orthogonal experiments for inorganic salts were carried out, as well as their optimal concentration values. The flocculation rate was used to determine the flocculation effect. Results obtained herein showed that the optimal medium composition for bioflocculant-producing Bacillus fusiformis was as follows: sucrose was the optimal carbon source at a concentration of 50 g/L with a flocculation rate of 42.2%; beef extract was the optimal nitrogen source at a concentration of 5 g/L with a flocculation rate of 49.8%; and the optimal inorganic salt was 0.5 g/L of AlCl3 with a flocculation rate of 48.3%. Through comparison of initial and optimized media for Bacillus fusiformis, it was found that the flocculation activity of the optimized medium was increased by 65%, while the yield increased by 16%. The optimal medium for bioflocculant-producing Bacillus fusiformis presented in this study is a useful reference for bioflocculant application.