Study On Screening、Characteristics And Starter Culture Of Chlorpyrifos Degrading Bacteri

With the widespread use of high-efficiency broad-spectrum organophosphorus pesticides such as chlorpyrifos in agricultural production,its impact on human health cannot be ignored.Eliminating or reducing the residues of organophosphorus pesticides in food has become a research hotspot.Therefore,this paper takes beneficial Yeast and Lactic acid bacteria as the research object,studies the degradation characteristics of degrading organophosphorus pesticide chlorpyrifos,and preliminarily explores the degradation mechanism.The fermentation agent is made by co-culture to explore its fermentation characteristics and the ability to degrade chlorpyrifos pesticide.The main research results are as follows :(1)In the early stage of the research group,50 strains of beneficial strains were screened,and their growth in chlorpyrifos at a concentration of 0～700 mg/L was determined.Nine strains of Lactic acid bacteria and six strains of Yeast with good growth characteristics were screened out.The degradation rates of nine strains of Lactic acid bacteria and six strains of Yeast in chlorpyrifos at a concentration of 100 mg/L were determined.Finally,one strain of Pediococcus pentosaceus 9b1 and one strain of Wickerhamomyces anomalus QF-1-1 with the highest degradation rate were screened out,and the degradation rates were 56.52 ± 0.71 % and 71.48 ± 0.02 %,respectively.(2)The ability of Pediococcus pentosaceus 9b1 and Wickhamomyces anomalus QF-1-1 to degrade chlorpyrifos was determined at different temperatures,inoculation amounts,p H and different chlorpyrifos concentrations.The results showed that when the culture temperature was 37 °C,the inoculation amount was 4 %,the p H value was 6,and the chlorpyrifos concentration was 100 mg/L,Pediococcus pentosaceus9b1 could degrade 68.02 ± 0.07 % of chlorpyrifos;when the culture temperature was 30 °C,the inoculation amount was 4 %,the p H was 5,and the chlorpyrifos concentration was 100 mg/L,W.anomala QF-1-1 could degrade 71.91 ± 0.19 % of chlorpyrifos.By fitting the first-order kinetic model,it was found that the relationsh-ip between the degradation rate of Pediococcus pentosaceus 9b1 and Wickhamomyc-es anomalus QF-1-1 and time showed a good linear relationship.The results showed that temperature,inoculation amount,p H and different chlorpyrifos concentrations had an effect on the degradation of chlorpyrifos by the strain.By measuring the residual amount of chlorpyrifos in the cell lysate and extracellular fermentation supe-rnatant of Pediococcus pentosaceus 9b1 and Wickhamomyces anomalus QF-1-1,it was found that the residual amount of chlorpyrifos in the extracellular fermentation supernatant decreased,and the cell lysate contained a certain amount of chlorpyrifos.It was speculated that the degradation mechanism of chlorpyrifos by the strain inclu-ded both extracellular degradation and bacterial adsorption.(3)The co-culture test of Pediococcus pentosaceus 9b1 and Wickerhamomyces anomalus QF-1-1 with high ability to degrade chlorpyrifos was carried out.Finally,it was concluded that when the culture temperature was 38.10 °C,the total inoculation amount was 5.96 %,and the inoculation ratio of Pediococcus pentosaceus 9b1 and Wickerhamomyces anomalus QF-1-1 was 2 : 1,the titration acidity was 99.52 ° T,and the content of diacetyl was 50.49 mg/L.The degradation ability of chlorpyrifos was determined.Compared with single culture,the co-culture starter had stronger degradation ability and could degrade 80.33 ± 0.58 % of chlorpyrifos.