OPTIMIZATION STUDIES ON BIODEGRADATION OF CYPERMETHRIN USING INDIGENOUS SOIL MICROORGANISM

Abstract

Degradation of cypermethrin using an isolate designated as Bacillus safensis, significantly enhanced degradation after acclimatization at a concentration 50 mgL−1of cypermethrin in selective media. An optimum growth of isolate was exhibited at an initial concentration of 100 mgL−1 of cypermethrin. However, the transformation wasinhibited at higher concentrations above 150 mgL−1, making inhibitory effect ofpesticide obvious. Based on the Gas chromatographic analysis, in semi-continuous bioreactor studies, KY752364 was able to metabolize 88.3% of cypermethrin, with an increasing efficiency by each cycle. Moreover, the decrease in rate of removal of cypermethrin was observed i.e. 89.8% in 2 days. All the biodegradation is associated with the growth of bacteria. In present study, KY752364 adapted quickly to the environment without any apparent lag phase and degraded cypermethrin rapidly at the start of incubation. The results indicated that Bacillus safensis possess a potential to be used in bioremediation of cypermethrin contaminated environment. This is very beneficial for field scale application as viable population was maintained by Bacillus safensis over a long period of time. For validation of experimental data various kinetic models both inhibitory and non-inhibitory were applied. The parameters of Andrew model of kinetics were estimated to be μmax: 0.175 h-1, Ks: 28.34 mgL−1 and Ki 210.06mgL−1. The high R2 (0.9962) approaching to 1 proposes that this substrate-inhibitionmodel is adequately fitted with the experimental data. Key words: Cypermethrin, Bacillus safensis, Metabolites, Degradation, Gas Chromatography, Environmental Sustainability