Abstract:

The optimization of fermentation medium of Bacillus megaterium and the research on its phosphorus solubilization effect can lay a theoretical foundation for its further research and production application. Using Bacillus megaterium as the test material, the fermentation medium conditions were optimized by orthogonal experiments, and the phosphorus solubilization effect was determined by the molybdenum antimony colorimetric method. The best medium and conditions were bran of 1%, soybean meal of 0.5%, NaCl of 1%, MnSO₄ of 0.05%, pH 7.0, temperature of 30℃, inoculation amount of 8%, rotational speed of 200 r/min, and the effective number of viable bacteria could reach 29×10⁸ cfu/mL. The 50 L fermentor reached basically the end in 26 hours, and the effective number of viable bacteria could reach 48×10⁸ cfu/mL and the spore rate could be greater than or equal to 95%. Bacillus megaterium was cultured in lecithin and calcium phosphate liquid medium for 5 days, the available phosphorus content in the supernatant was 1.67 mg/L and 83 mg/L, respectively, which was 26 times and 17 times that of the control group. After 2 weeks of treatment in field test, the available phosphorus content in soil was 165.3 mg/kg. Through this study, the effective number of viable bacteria is 7 times higher than that of the original formula, which can effectively degrade organic and inorganic phosphorus, and significantly increase the effective phosphorus content in soil.

Key words: Bacillus megaterium, fermentation medium, available phosphorus content, effective number of viable bacteria, spore rate