Biodegradation of mixed pesticides by mixed pesticide enriched cultures.

This paper discusses the degradation kinetics of mixed (lindane, methyl parathion and carbofuran) pesticides by mixed pesticide enriched cultures (MEC) under various environmental conditions. The bacterial strains isolated from the mixed microbial consortium were identified as Pseudomonas aeruginosa (MTCC 9236), Bacillus sp. (MTCC 9235) and Chryseobacterium joostei (MTCC 9237). Batch studies were conducted to estimate the biokinetic parameters like the maximum specific growth rate (mu(max)), Yield Coefficient (Y(T)), half saturation concentration (K(s)) and inhibition concentration (Ki) for individual and mixed pesticide enriched cultures. The cultures enriched in a particular pollutant always showed high growth rate and low inhibition in that particular pollutant compared to MEC. After seven weeks of incubation, mixed pesticide enriched cultures were able to degrade 72% lindane, 95% carbofuran and 100% of methyl parathion in facultative co-metabolic conditions. In aerobic systems, degradation efficiencies of lindane methyl parathion and carbofuran were increased by the addition of 2g L(- 1) of dextrose. Though many metabolic compounds of mixed pesticides were observed at different time intervals, none of the metabolites were persistent. Based on the observed metabolites, a degradation pathway was postulated for different pesticides under various environmental conditions.