Degradation of carbofuran by rhizosphere soil microorganisms

Abstract

An ability of rhizosphere soil microorganisms to degrade carbofuran was investigated. An enrichment technique was used to isolate carbofuran degraders from carbofuran phytoremediated rhizosphere soils in C-, N- and C and N-limited Basal Salt Media (BSM) containing 5 mg/L of carbofuran. The shortest half-life of carbofuran, 3 days, was found in C-limited BSM cultured with an isolate named PCL3 indicating that carbofuran was used as a sole C-source. PCL3 was identified as Agrobacterium radiobacter and was further used in the bioaugmentaion study. Carbofuran dissipation in rhizosphere soils of 6 weeds i.e. Umbrella sedge (Cyperus iria L.), Water primrose (Jussiaea linifolia V.), Fuzzy flatsedge (C. pilosus V.), Small flower umbrella plant (C. difformis L.), Tall-fringe-rush hoorah grass (Fimbristylis miliacea V.) and Cover fern (Marsilea crenata P.) was conducted. Rhizosphere soil of Fuzzy flatsedge was selected to use in the bioaugmentation experiment because of the shortest half-life of carbofuran in this soil (15 days). Bioaugmentation of carbofuran using PCL3 was conducted to examine its ability to degrade carbofuran in Fuzzy flatsedge rhizosphere soil. The degradation of carbofuran in this soil was not improved by PCL3 suggesting that rhizosphere remediation might be enough for remediating carbofuran contaminated soil. An ability of PCL3 to degrade carbofuran was evident in bulk soil (t1/2 of 12 days) and autoclaved soils (t1/2 13-14 days) when compared to soils without an inoculation (t1/2 of 58 days). In conclusion, rhizosphere remediation is one of the effective bioremediation techniques to remove or detoxify carbofuran residues in soil. Bioaugmentation of carbofuran in contaminated bulk soil by isolated degraders could improve the degradation of carbofuran.