Optimization of Fermentation Conditions for Bacillus subtilis HAB-1 to Produce Antimicrobial Substances

Key words: 
• Bacillus subtilis /
• plate confrontation /
• shake flask fermentation /
• optimization

Abstract: An attempt was made to determine the optimal medium for Bacillus subtilis HAB-1 growth and the best fermentation conditions for Bacillus subtilis HAB-1 to produce anti-microbial substances. Suitable C source,N source and metal ions were screened for the medium and the cultural conditions determined for the strain HAB-1 through single factor test with the methods of shake flask culture and plate confrontation. The optimal carbon source was sucrose and corn flour,the optimal nitrogen was yeast extract and bran,and the optimal metal ions were K+. Orthogonal experiment showed that HAB-1 had the strong anti-microbial activity against pathogen when cultured in the medium ZY. This medium contained 10 g·L^-1sucrose,30 g·L^-1 corn flour,30 g·L^-1yeast extract,40 g·L^-1bran,and 1 g·L^-1KH₂PO₄. The culture conditions for this medium were further optimized. The optimal cultural conditions of this medium were pH 6. 0,the fermentation temperature 37 ℃,the medium volume 60 mL in a 250 mL flask,the inoculation volume ratio 2%（ V/V）,the fermentation time 24 h,and the rpm 190 r·min^-1. Under these culturing conditions,the strain HAB-1 had the largest viable count and the highest antimicrobial activity against anthracnose pathogen in rubber tree. The viable count and inhibition zone diameter were 2. 6 × 10¹⁰/ mL and 34. 0 mm,respectively,123. 81 times and 1. 10 times higher than those of the strain HAB-1 cultured in NB.