Optimization of diazinon biodegradation from aqueous solutions by Saccharomyces cerevisiae using response surface methodology

Diazinon is an organophosphate compound that inhibits the activity of acetylcholinesterase. Standards of the World Health Organization and Environmental Protection Agency for diazinon concentration in water are 0.1 and 9 × 10−6 mg/L, respectively. The aim of this study was the optimization of diazinon biodegradation from aqueous solutions by Saccharomyces cerevisiae using the response surface methodology (RSM). Harvested cells of S. cerevisiae were locally purchased from the Iranian Research Organization for Science and Technology. To obtain the optimum condition for diazinon biodegradation using RSM, input parameters included the initial concentration of diazinon (0.01–10 mg/L), concentration of S. cerevisiae (0.5–5%), pH (4–10), and retention time (1–30 h). The research study had a central composite design where one of the methods was RSM. According to the results, the observed values of the removal efficiency of diazinon were variable in the range of 23–96. The highest removal rate was obtained as 96% under the initial diazinon concentration of 2.5 mg/L, S. cerevisiae concentration of 3.88%, pH of 5.5, and retention time of 22.75 h. The results displayed that the removal efficiency of diazinon had a direct relationship with the concentration of S. cerevisiae and retention time, and an inverse relationship with pH and the initial concentration of diazinon. We can conclude that S. cerevisiae has the ability to remove diazinon with the lowest cost and a high efficiency.