Date

2022-5-26

Author

Kokangül, merve

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Cypermethrin (CYP) is a commonly used type Ⅱ pyrethroid for the protection of both agriculture and household, causing serious secondary environmental pollution. Environmentally friendly and effective techniques such as biodegradation can minimize or remove the contaminants and their potentially harmful metabolites from the environment. In this study, two bacterial strains isolated from agricultural soil obtained from fig farms in Adana were identified as Enterobacter hormaechei ZK101 and Stenotrophomonas maltophilia ZK102. ZK101 and ZK102 were found efficient in degrading CYP under different conditions converting CYP to 3-PBA. The maximum CYP degradation was observed at 33.9 °C, pH 6.7 with an initial CYP concentration of 5.69 mg. L-1 for ZK101 and at 38.1°C, pH 6.7 with an initial substrate concentration of 6.6 mg. L-1 CYP for ZK102. Under these conditions, 67.6% of cypermethrin for ZK101 and 81.9% of cypermethrin for ZK102 were degraded in a minimal salt medium within 5 days. While CYP was degraded accumulation of 3PBA was observed. Since the toxicity of 3-PBA is much higher than CYP, the accumulation of 3-PBA by CYP degraders would be an environmental problem. Therefore, degradation kinetics of CYP (4 mg L-1) in soils inoculated with isolates ZK101 and ZK102 was established. Time-dependent removal of cypermethrin with rate constants of 0.468, 0.257 d-1for ZK101 and ZK102 following first-order rate kinetics was observed in soil, and time-dependent removal of 3PBA with rate constants of 0.406 and 0.278 d-1, respectively. Since both strains converted the CYP to 3-PBA the first enzyme was analyzed using crude cell extracts. Enzyme assays with crude cell extracts showed an activity of equivalent of esterase. This study is one of the first studies that identified the CYP biodegradation pathway and estimated rate constants of biodegradation and 3-PBA accumulation of the isolates obtained from fig farms using the commercially available CYP. Estimating those constants helps predicting the possible negative effect that microbial activates could cause and will provide an insight of the pesticides biodegradability that could be used while potential pesticides are being applied.

Subject Keywords

Pyrethroids, Cypermethrin, Biodegradation, E. hormaechei, S. maltophilia

URI

https://hdl.handle.net/11511/97893

Collections

Graduate School of Natural and Applied Sciences, Thesis