Screening, Identification And Characterization Of Organophosphate Pesticide Degrading Fungus

Dimethoate are widely used for insects control in many countries. However it caused serious problems to the environment and agricultural products because of its toxicity and refractoriness, which has become a public concern. Degradation of pesticides by microorganism is one of the most important methods.We isolated a passel of microorganism from soil polluted by dimethoate for many years. There were over 200 bacteria strains and over 100 fungal strains totally. By more isolation and domestication, we obtained three fungal strains which could grow on culture medium with very thick dimethoate, we named them L1, L2, L3. By gas chromatographic(GC) techniques the degradation activity of these three fungal strains were determined, L1, L2, L3 could degrade dimethoate 230mg/L, 245mg/L,280mg/L in 120h respectively, which showed us that they all occurred high rated biodegradation. So we select strain L3 having a further study. On the basis of morphous viewing, the strain was idendified as Aspergillus spp. Further, we identified L3 by ITS method. Primers were designed blow: 18SF : 5'-TCCGTAGGTGAACCTGCG-3'; 28SR :5'-TATCCCTACCTGATCCGAG-3'. Then PCR, the produces of PCR were cloned and sequenced, and searched in GenBank+EMBL+DDBJ+PDB database, on the basis of phylogenetic inference based on ITS sequence and analysis the strain was idendified as Aspergillus nomius. The strain was able to utilize dimethoate when carbon source coexisted. Strain L3 could endure high concentration of dimethoate. In flask test Strain L3 degraded 29.2% of dimethoate(2000mg/L) within 120h, and the maximum tolerance concentration of dimethoate reached 6000mg/L. For strain L3, the optimum pH and temperature for the growth and the degradation of dimethoate was 28℃, 7.0 respectively. and it could grown well in 25-40℃and pH6.0-pH9.0, Strain L3 was also able to degrade other organophosphates well such as phoxim and acephate. When the concentration reached 5000mg/L strain L3 could degrade 877 mg/L 95.3% phoxim and 461 mg/L 65.9% acephate in 120h. These results indicated that the degradability of strain L3 was broad-spectrum. The result from the field experiments in small areas showed that L3 had obvious effects on the removal of residual dimethoate in soil(13.0mg/Kg·7d), but to...