Effect of culture acclimation on the kinetics of aldicarb insecticide degradation under methanogenic conditions

This study reports on the kinetics of aldicarb transformation under methanogenic conditions using batch reactors containing acclimated and unacclimated cultures under controlled conditions. Culture acclimation was accomplished by exposing anaerobic microorganisms maintained in a semi-batch reactor to low concentrations of aldicarb. Results of the kinetic studies showed that in an anaerobic system aldicarb is converted to aldicarb nitrile by the hydrolytic pathway. Analysis of the hydrolysis/dehydration rate constants showed that anaerobic cultures enhanced the rate of conversion of aldicarb by 4-fold for acclimated cultures and by 2-fold for unacclimated cultures compared to the rate of abiotic hydrolysis (p < 0.05). Only the acclimated cultures were able to further mineralize the reaction intermediate aldicarb nitrile. Michaelis-Menten and Monod kinetics adequately defined the aldicarb nitrile degradation.