Pesticide Of Cis-Cypermethrin Biodegradation Law Research

The pesticide of cis-cypermethrin is hydrophobic and stable, have a long half-life, cause the cypermethrin residue accumulated in the farmland environment, the pollution problem is serious. Biodegradation is considered as an safe and effective treatment methods and does not cause secondary pollution.Extracellar crude enzyme, having the ability of cypermethrin-degradation, was extracted from pseudomonas aeruginosa GF31, which was screened and preserved in the lab. The exoenzyme molecular weight was more than10kDa. The degradation activity of the exoenzyme could keep stable in the pH range between5.0and9.0and temperatures range between20℃and70℃, with the optimal pH about of7.0and optimal temperature about of60℃.The cypermethrin-degradation kinetic of the crude enzyme was studied in detail. The results indicated that the biodegradation rate of cypermethrin conformed to Michaelis-Menten formula, with pH7.0and temperature30℃, the Michaelis-Menten’constant(Km) was30.38μg·L-1, the maximum velocity(Vmax) was33.78μg·(L·min)-1. The biodegradation process was proved to agree with the first-order kenitic model and the non-linear kinetic model at different pH and temperature. The first-order kenitic correlation coefficient R2 was greater than0.9, the non-linear kenitic correlation coefficient R2was greater than0.97. The measured data and the fitting curve by the two kinetic model were good in PH5.0～9.0, the enzyme biodegradation dynamics had wider pH range, in contrast, the nonlinear dynamics fitting degree was higher in different tempermetures.It is found that the Pseudomonas aeruginosa GF31could grow in the medium with50mg·L-1cypermethrin was used as the sole carbon source, the degradation rate was35.41%in7d. When the medium contained0.5g·L-1ammonium sulfate, When the medium contained1.0g·L-1glucose, When the medium contained1.0g·L-1peptone, the degradation rate was promotion. Especially, the degradation rate was81.00%, which was obtained when added amount peptone in the medium as the nitrogen source.The results showed that the GC-MS primary degradation products of cypermethrin were2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropanecarboxylic acid(DCVA) and3-phenoxybenzoic acid(3-PBA), then further decomposed. The intermediate product DCVA and3-PBA concentration decreased after reaching a maximum during the two degradation processes. But the start time of the intermediate products of the enzyme degradation appeared than the Pseudomona aeruginosa GF31in advance.