Experimental Study On Degradation Of Parathion-Methyl By Immobilized Bacteria

The organophosphorus pesticide occupies an important position in control of pests and diseases, which are the most production and useness of pesticide varieties in the world. However, due to the toxicity and the nonstandard useness of organophosphorus pesticide, which was the main factor of soil pesticide contamination, and harm human health directly or indirectly. Therefore, developing contaminated soil bioremediation technology research is of great significance.Three preponderant pure strains were screened and gotten from the long-term pesticides pollution soil lixivium, noted for the bacteria A1, A2, and A3respectively. According to the bacteria16S rDNA genetic sequence, combining with the experimental results of bacteria morphology observation, physiological and biochemical, referring to <Bergey’s Mannul of Determinative Bacteriology(8th edition)>, three strains were determined to be microbe of Clostridium, Bacillaceae, the strains A1,A2and A3was respectively determined to be Bacillus pasteurii, Clostridium butylicum, Clostridium acetobutylicum. Through the preliminary domestication, among three strains, strain A3owned the best tolerance of concentration of parathion-methyl for500mg/L, so the A3was to be research object, via the best growth conditions and growth curve experiment of bacteria, it was obtained that the best growth conditions of strain A3, the best growth temperature was35℃, pH value of the optimum starting was7, the best C, N source was starch and yeast paste respectively, the best growth speed was120r/min. Train A3was cultured in beef peptone liquid medium, grow faster in8hours, the delay period was not apparent, logarithmic rise period was longer and achieved maximum biomass at72h.Through the strain’s degradation process curve experiment, tolerability experiment and the effect substrate concentration on degradation rate experiment, it was obtained that the three bacteria reached the highest degradation rate in12h, which was respectively73.04%,78.05%and85.51%, the biggest tolerant concentration of bacteria A2and A3was respectively600mg/L and800mg/L; According to the generation experimental study of strain A3, which indicated that bacterium A3was more stable, not easily mutate.This paper also systematically studied the degradation quality of immobilized bacterium A3on parathion-methyl and the influence factors, determined that the optimal immobilization method was crosslinking, the optimal immobilization carrier was the corn core, the optimal degradation time was12h, the optimal crosslinking agent concentration was0.5%, the optimal degradation pH was7, and then the degradation effect of immobilized bacterium A3on parathion-methyl was the best, and the maximum biodegradable rate was85.21%.This research lays the foundations for the technology application of pesticide contaminated soil bioremediation, which has certain value of practical application.