Microorganisms trigger chemical degradation of diazinon

Many processes in the environment are both chemically and/or microbiologically driven. In this paper we present a simple method to evaluate the extent of microbially driven organophosphorus insecticide diazinon degradation. Microorganisms isolated from soil samples have been grown in the minimal growth media where diazinon served either as a sole or as an additional carbon source. Diazinon was extracted with ethyl acetate and its concentration was determined by GC/μECD system. Isolated microorganisms enhanced degradation of diazinon up to a 30-fold at neutral pH. The fast biodegradation of diazinon at neutral pH was only possible when diazinon was dissolved in the organic solvent (i.e. ethanol, n-heptane, methanol and dimethyl sulfoxide). Diazinon degradation in organic solvent correlated with pH decrease in the growth medium. A decrease of pH was a consequence of microbial metabolism of the solvent. When the initial pH of the growth medium was lower than 4.5 the addition of microorganisms had no effect on the rate of diazinon degradation. The results suggest a tight link between microbiology and chemistry in the degradation process.