Aerobic degradation of technical hexachlorocyclohexane by a defined microbial consortium

Organochlorine pesticides including hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) are largely used in developing countries like India for public health and agricultural purposes. Even though the agricultural use of technical mixture (tech-HCH) is banned, countries like India are still using gamma-HCH for economic purposes. Thus, in addition to already contaminated sites, new sites are being contaminated with gamma-HCH and its stereoisomers. In the environment, these isomers have a half-life of 8-10 years. In our laboratory, we developed a microbial consortium capable of degrading tech-HCH. Conditions such as induction, inoculum level, concentration of the substrate, pH of degradation and interaction between isomers were optimized for tech-HCH degradation. Up to 25 ppm tech-HCH was degraded at an inoculum level of 100 microg protein/mL, pH 7.5 at ambient temperature (26-28 degrees C). The degradation of HCH-isomers was in the order of gamma>alpha>beta>delta. The rate of degradation was also determined.