The Study Of Fermentation Conditions Of Bacillus And Application In Fish Pond Water

In this paper the fermentation conditions, optimized medium of the two strains including Bacillus cereus DLSL-2 and Bacillus subtilis XF-1 were studied. The effect of application in fish pond water were evaluated.The fermentation conditions of Bacillus cereus DLSL-2 were investigated through single-factor and uniform design tests. The optimized fermentation conditions and medium were: temperature 30℃, initial pH 7.0, and shaking at 250r/min, 5.6% inoculum. The most suitable medium was identified as following: soybean power 4.88g, maize starch 1.45g, yeast extract 1.78g, K₂HPO₄0.11g, CaCl₂0.01g, MgSO₄ 0.15g, MnSO₄0.01g, distilled water 100mL. The viable number of Bacillus cereus DLSL-2 in the optimized medium could raised to 7.1 × 10⁹cfu/mL which significantly higher than that in the non-optimized medium.The single-factor test and response surface analysis were used to determine the optimized fermentation conditions and medium of XF-1 . The experimental results showed that the most suitable fermentation conditions and medium were : temperature 37℃, initial pH 7.2⁷.5, shaking at 250r/min, 6% inoculum. The most suitable medium was identified as following: maize starch 2.53g, soybean power 4.95g, yeast extract 1.30g, CaCl₂0.01g, K₂HPO₄0.11g, MgSO₄0.15g, MnSO₄0.01g, distilled water 100mL, shaking time 22h. The results demonstrated the viable number of Bacillus subtilis XF-1 in the optimized medium could raised to 24.5 × 10⁹cfu/mL which significantly higher than that in the non-optimized medium.In application experiment, 5mL per cubic meter of the bacillus broth culture was inoculated into fish pond water. The result showed the application of bacillus culture could efficiently decompose pollutants and the organic substances in the fish pond water. The concentrations of NH₄⁺-N, NO₂^--N, COD were reduced significantly comparing with the non-inoculating control. The mixed inoculation of the two bacillus strains experimental groups should better effect than that of single strain in water purification. The remove rate of NH₄⁺-N, NO₂^--N, COD were 99.16%, 97.86 and 78.72%, respectively.