Rapid biodegradation of diazinon using a novel strain of Candida pseudolambica
Tahmineh Ebadi, Ghasem Najafpour, Habibollah Younesi, Maedeh Mohammadi
Abstract
Diazinon has been widely applied in the agricultural sector as an organophosphorus insecticide because of its toxicity, while it is a serious threat to the biodiversity of the environment. A yeast strain being capable of biodegrading diazinon was isolated from pesticide-contaminated agricultural soil. Analysis of sequences spanning the Intergenic Spacer (ITS) region showed that the isolated strain was Candida pseudolambica. The ability of this strain for diazinon biodegradation was evaluated, and the condition of the aqueous solution was optimized applying response surface methodology (RSM) and validated by the artificial neural network (ANN). At the optimum condition, in a mineral salt medium (MSM) containing a high concentration of diazinon (775 mg/l) and 2.25 g/l glucose as a co-substrate with an inoculum size of 8% and incubated at 30 °C, the isolated strain of C. pseudolambica demonstrated 69.6% removal of diazinon in a short period of time (24 h). Substantial biodegradation efficiency (34%) was also achieved after 24 h incubation of the isolate in a medium that 500 mg/l of diazinon was utilized as the only carbon source. The optimum ANN model obtained with 5 neurons in the hidden layer resulted in R2 > 0.98, and for the RSM, R2 was 0.993. Results indicated the remarkable ability of the isolated strain for rapid degradation of high concentrations of diazinon, which could be promising for large-scale bioremediation applications.