Screening Chlorpyrifos Degrading Bacteria From Composing And Research Of Bio-surfactant Produced In The Process

In this dissertation, taking chlorpyrifos as a model pollutant, 4 strains of bacterium capable of highly degrading chlorpyrifos was screened from the sample of agriculture aerobic compositing collected after taming and enrichment. Based on analysis of Phenotype, physiological and biochemical characters, degradation capacity of strains were studied systematically following environmental variations. According to the properties of bacterium producing bio-surfactant, Strain BS-2 was selected as a mainly research object to research the optimal condition of cultivation, and to definite the type of bio-surfactant. The results could be summarized as follows:4 strains were screened after taming and enrichment, there were marked as BS-2, BS-4, BS-5, BS-6. The degradation rate of 200mg·L^-1 chlorpyrifos by the 4 strains were 82.9%, 73.7%, 72.2% and 71.9%. According to phenotype, physiological and biochemical experiment, the 4 strains were identified as Bacillus sp., Pseudomomae sp., Hafnia sp., and Azomonas sp.The effect of carbon source, nitrogen source, inoculation quantity, pH, temperature and culture period on degradation was determined. The result showed that the degradation rate of 200mg·L^-1 chlorpyrifos by the 4strains would increase from 82.9%, 73.7%, 72.2% and 71.9% to 89.7%, 84.5%, 85.4% and 88.9% respectively, when environment factors were optimized.These 4 strains were could depress the surface tension of fermentation liquor less than 40mN·m^-1, Strain BS-2 was selected as sample to further research,which could keep stable at temperature from 20¹00℃and pH from 6.0⁹.5. The C source and N source of the strain were respectively identified as soluble starch and NH4NO3 by using single factor experiment method. The cultural conditions of the strain were optimized by using orthogonal experiment method. The optimized fermentation conditions were: soluble starch 25.0 g·L^-1,NH4NO3 8.0 g·L^-1,KH2PO₄ 2.0 g·L^-1,K2HPO₄ 2.5 g·L^-1,KCl 1.1g·L^-1,NaCl 1.1g·L^-1, MgSO₄ 0.15 g·L^-1,FeSO₄·7H20 5×10-5 g·L^-1,EDTA 1.0 g·L^-1,yeast paste 0.2 g·L^-1,initial pH 7.0,temperature 30℃,rotation speed 150r/min,culture time3d. The bio-surfactant that was purified from the strain B2 was identified as a cyclic lipopeptide analogue via the analysis of TLC and FT-IR. The pure lipopetide could depress the surface tension of pure water from 72.3mN·m^-1 to 29.9mN·m^-1 and the CMC was 0.139g/l. Experimental result indicated that there really were bio-sarfactant-producing microorganisms during composting and that have favorable surface activity.