Isolation and acclimation of a microbial consortium for improved aerobic degradation of alpha-hexachlorocyclohexane

A microbial consortium that can utilize alpha-hexachlorocyclohexane (alpha- HCH) as a sole source of carbon and energy was isolated,from soil and sewag e through a novel technique involving an initial enrichment in a glass colu mn reactor followed by a shake flask enrichment. This consortium took 14 da ys to completely mineralize 5 and 10 mu g mL(-1) alpha-HCH in mineral salts medium in shake flasks. The degradative ability of this consortium improve d very markedly on acclimation by successive and repeated passages through media containing increasing concentrations of alpha-HCH; The acclimated con sortium could degrade 100 mu g mL(-1) of alpha-HCH within 72 h at a degrada tion rate of 58 mu g mL(-1) day(-1) with concomitant release of stoichiomet ric amounts of chloride; Accumulation of any intermediary metabolites was n ot detected in the culture broth as tested by TLC and GC, Implying complete mineralization of the substrate. The acclimated consortium contained eight bacterial strains and a fungus. The individual strains and the different p ermutations and combinations of them, however, were able to utilize only 10 mu g mL(-1) of or-HCH. Mesophilic temperatures (20-30 degrees C) and near- neutral pH (6.0-8.0) were most favorable for alpha-HCH degradation. Among t he auxiliary carbon sources tested, ethanol, benzoate, and glucose (at high er concentrations) retarded the degradation of alpha-HCH, whereas the addit ion of cellulose, sawdust, and low concentrations of glucose (<200 mu g mL( -1)) and acetone enhanced the rate of degradation.