Microbial degradation of recalcitrant pesticides: a review

Some pesticides such as organochlorines are of critical environmental concern because they are highly persistent due to their stable chemical nature. As a consequence, even after banning, dichlorodiphenyltrichloroethane and endosulfan can be detected at concentrations above permissible limits. Moreover, classical pesticide degradation of these compounds using physiochemical processes is limited. Alternatively, biodegradation using microorganisms isolated in contaminated sites appears promising. For instance, the bacterium Pseudomonas fluorescens degrades aldrin by 94.8%, and the fungus Ganoderma lucidum can bring down the levels of lindane by 75.5%. In addition, the toxicity is reduced by enzymes that perform oxidation, reduction, hydrolysis, dehydrogenation, dehalogenation and decarboxylation. Then, the metabolites are further degraded by mineralisation and cometabolism. The biodegradation process can be manipulated by applying techniques such as bioattenuation, bioaugmentation and biostimulation. This article discusses the latest advances in microbial degradation of recalcitrant pesticides.