Isolation and Acclimation of a Microbial Consortium for Improved Aerobic Degradation of α-Hexachlorocyclohexane

Abstract

A microbial consortium that can utilize alpha-hexachlorocyclohexane (alpha-HCH) as a sole source of carbon and energy was isolated from soil and sewage through a novel technique involving an initial enrichment in a glass column reactor followed by a shake flask enrichment. This consortium took 14 days to completely mineralize 5 and 10 microg mL(-)(1) alpha-HCH in mineral salts medium in shake flasks. The degradative ability of this consortium improved very markedly on acclimation by successive and repeated passages through media containing increasing concentrations of alpha-HCH. The acclimated consortium could degrade 100 microg mL(-)(1) of alpha-HCH within 72 h at a degradation rate of 58 microg mL(-)(1) day(-)(1) with concomitant release of stoichiometric amounts of chloride. Accumulation of any intermediary metabolites was not 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 permutations and combinations of them, however, were able to utilize only 10 microg mL(-)(1) of alpha-HCH. Mesophilic temperatures (20-30 degrees C) and near-neutral pH (6.0-8.0) were most favorable for alpha-HCH degradation. Among the auxiliary carbon sources tested, ethanol, benzoate, and glucose (at higher concentrations) retarded the degradation of alpha-HCH, whereas the addition of cellulose, sawdust, and low concentrations of glucose (<200 microg mL(-)(1)) and acetone enhanced the rate of degradation.

Bioremediation of Hexachlorocyclohexane Contaminated Soil: Field Trials

“…Microbial degradation of all the HCH-isomers has since been observed under oxic conditions both in soil (Bachmann et al, 1988 b); Doelman et al, 1985;Sahu et al, 1993) and in pure cultures of microorganisms Thomas et al, 1996). We have isolated in our laboratory a microbial consortium consisting of ten bacterial isolates which have got the capacity to degrade HCH (Manonmani et al, 2000;Murthy and Manonmani, 2007) under oxic conditions. Translation of the laboratory scale trials to small plots and actual open fields was studied in soil The defined microbial consortium used in the degradation of tech-HCH was developed by the long-term enrichment of the contaminated soil and sewage samples.…”

“…-and -isomers have been reported to be degraded rapidly under aerobic and anaerobic conditions. -and -isomers were degraded first in 12 h of incubation (Manonmani et al 2000, Johri et al 1998, Datta et al 2000, where as -isomer was found to remain undegraded under similar environmental conditions (Bachmann et al 1988a, Beurakens et al 1991. The degradation of different isomers of HCH has been shown to be dependent on many features mainly the type of microorganism used, aeration, the adaptability of these microorganisms to the pollutants (Moreno and Buitron 2004), type of carbon source to cultivate them (Radha et al 2010), pre-exposure of the used organism to the pollutant (Bidlan and Manonmani 2002), etc.…”

“…The microbial consortium capable of degrading Tech-HCH was developed in our laboratory by long term enrichment of HCH contaminated soil and sewage according to Manonmani et al [2000]. The Tech-HCH degrading consortium that got enriched was acclimated with increase in concentration of Tech-HCH from 5 to 25 ppm.…”

“…HCH-degrading microbial consortium developed by the long-term enrichment of the contaminated soil and sewage samples (Manonmani et al, 2000;Bidlan and Manonamani, 2002). This was reconstituted by mixing the different consortia having the ability to degrade -,-,-and -HCH isomers.…”

Elimination of Inhibitory Effects of Chlorpyrifos and Quinolphos on Radish and Green Gram Seed Germination by Bioremediation of Contaminated Soil: A Comparative Study

“…The microbial consortium capable of degrading chlorpyrifos and quinolphos was isolated in the laboratory by long-term enrichment technique (Manonmani et al, 2000). Individual strains of Chlorpyrifos and quinolphos degrading consortium,…”