Isolation And Degrading Characteristics Of Avermectin Degrading Bacteria

Abamectin has been considered as the best and widely used veterinary anthelmintic at present, drug residues to environment have been brought by a devil of applications, not only formation of resistant strains will be induced, but also ecological environment will be destroyed by these residues, without doubt, serious pollution problems will be followed. The technology of biodegradation has been developed rapidly in recent years, and it has become one of the most effective ways to solve problem of drug residues in the environment. Screening model of the highly effective degeneration bacterium was established in the study, and degeneration characteristics of the strain were also studied.A high performance liquid chromatography (HPLC) method was developed for determination of Avermectin (AVM).Ehylacetate was used for extracting Avermectin from medium. Mixture of methylate and H2O (92:8, V/V) was used as mobile phase in the HPLC analysis. The recoveries of Avermectin ranged from 86.95%~91.68% in medium, the coefficients of variation of AVM ranged from 2.3-3.0% and 3.0-5.0%, and the limit of quantitation (LOQ) of AVM was 0.5mg/L.A highly effctive screening model was built,in which enrichment was condueted by adding a definite Avermectin into the innutriment medium. By using direct spreading method,four strains of bacteria were isolated from soil, among which one strain showed the Avermectin degradation ability and that was named as AVM1 strain. The strain was identified as Bacillus cereus.The AVM1strain was considered as the goal strain for studying the generation characteristics. The AVM1 strain under the condition of pH7.0, temperature 35℃, the substrate concentration was the 40mg/L, and volume of medium was 100mL, a higher degeneration speed could be maintained. Adding carbon and nitrogen into the medium, degradation ability of the strain was enhanced. By adding soluble starch into the medium, the degeneration rate of the AVM1strain could be reached to 41% in the 40mg/L Avermectin solution for 6 days. The metal ions have a significant effect on Avermectin degeneration speed of the strain. In the study, the influence of 7 ions were investigated. The result showed that degradation ability of the strain was enhanced by adding 0.1% Cu2+, degeneration rate were 43.5%.Research of degeneration of AVM1 strain to the Ivermectin was also made under the same situation in the study. The result indicated that the strain didn't show degradation ability to the Ivermectin.