Isolation And Identification Of Degradation Bacteria For Synthetic Pyrethroids And Its Degradation Characteristics

Pyrethroids are a class of efficient, safe and novel insecticides, which were synthesized by scientists on the basis of the structure of natural pyrethrins through Chiral catalyst, optical rearrangement and other methods. With the prohibition of high toxic pesticides such as the organochlorine and orgnaophosphorus ones which are hardly biodegradable, the usage of Pyrethroids grows quickly, accounting for half of the total area of pesticide application in our country.After large amounts of utilization, pyrethrins were found highly toxic to aquatic life and non-target organisms, also harmful for human beings. The residues in the soil brought serious environmental pollution. Microorganisms play an important role in the bioremediation of pesticide residues, and the essence is to screen the strains capable of degrading pesticides efficiently.By enrichment of soil samples, an effective strain capable of degrading bifenthrin as a sole carbon source was isolated, and its degradative properties were investigated, as follows: (1)A bacterial named HLB-1 which could degrade the insecticide bifenthrin was isolated from the sludge in the watercourse of a pesticide factory of Hunan, and was identified as Delftia tsuruhatensis by analyses of morphology, physio-biochemistry features and 16S rDNA.(2)The investigation of the biological characteristics and tolerance to bifenthrin of the strain HBL^-1, indicated that pH7.0 and 30℃were the optimal condition of growth. It took 24 hours for the strain to reach index period when it was incubated in anorganic substrate supplemented with glucose, and the maximum bifenthrin concentration for the growth of the strain was found to be 600 mg·L^-1, while it could grow much better at 200 mg·L^-1 and 300 mg·L^-1.(3)The degradative properties of other pesticides by HLB-1were studied. The results indicated that the strain HLB-1 could simultaneously degrade fenvalerate, deltamethrin, cyhalothrin, and carbendazim, and the degradation rates were 30.87%,33.90%,45.69% and 21.76% respectively. (4)The optimal environmental conditions of degradation were studied, and the results showed that the optimal condition was pH 7.0, 30℃, inoculated amount at 100 mL·L^-1, bifenthrin concentration 250 mL·L^-1 mL. But bifenthrin could also be degraded under 20 30℃and pH 6.0 8.0. (5)The degradation of bifenthrin in soil by HLB-1 was simulated in the laboratory. Compared with sterilized soil, The residues in non-sterilized soil was 1.97 mg?kg^-1 lower than sterilized soil. Soil adding anorganic substrate was 6.59mg?kg^-1 less than soil adding deionized water in terms of residual volume of bifenthrin, the lowest being the ones added anorganic substrate and bacteria was 7.25mg·kg^-1. It showed that HLB-1 could fit into the simulation environment very well, without rivalry with indigenous microorganisms in the environment.