Metoxychlor bioremediation by indigenous actinomycetes using pure and mixed cultures

FUENTES, M.S.; S¨¢EZ, J.M.; BOURGUIGNON, N.; 1CUOZZO, S.A; BENIMELI, C.S.; AMOROSO, M.J.

Puc¨®n, Chile

Workshop; 2º Workshop y 5º Curso Internacional: Avances en Ciencia y Tecnolog¨ªa de Recursos Naturales; 2010

Metoxychlor biorremediation by indigenous actinomycetes using pure and mixed cultures   1Fuentes, M.S.; 1S¨¢ez, J.M.; 1 Bourguignon, N.; 1Cuozzo, S.A.; 1,3Benimeli, C.S. and 1,2,3Amoroso, M.J. 1PROIMI-CONICET, 2Fac. de Bqca, Qca y Fcia. UNT.3UNSTA. Tucum¨¢n, Argentina. soledadfs@gmail.com   Persistent organic pollutants (POPs) are compounds highly stable and bioaccumulative that has been known as ubiquitous environmental contaminants. Methoxychlor (MTX), like others organichlorine pesticides (OCPs), were used for purposes like insect and malaria control, sanitation and harvest optimization. Some of the OCPs were banned, but others continue to be used illegally. MTX is a developed pesticide for use as a replacement for DDT which was prohibited internationally since the 1970s. DDT and methoxychlor accumulate in the environment due to their resistance to biodegradation and are considered toxic and estrogenic, affecting to humans and mammals. Methoxychlor exerts only slight toxicity toward microbial populations in soil under aerobic conditions. The aim of this work was to evaluate the MTX removal capacity of isolated actinomycetes, individually and as mixed cultures under controlled laboratory conditions. Streptomyces sp. M7 (M7), Streptomyces coelicolor A3 (ScA3) and four indigenous actinomycetes isolates were cultivated individually in minimal medium (MM) with MTX for acclimation. These strains, as pure and consortia of two to six microorganisms, were cultivated in MM with MTX (1.66 mg L-1). Microbial cells were used to obtain cell-free extracts for dechlorinase activity assays and the supernatants from these cultures were used to determine residual MTX by gas chromatography. The isolates were characterized by 16S rDNA amplifications and sequenced. Enzyme activities ranged between 0.00 to 159.11 ¦ÌmolCl-/h/mg protein and MTX removal percentages ranged between 72 to 100%.  The mixed culture A3-A12- A14 showed the best activity but not the minimal residual MTX value.  Because of no linear relationship between residual MTX and enzyme activity, the ratio between these two parameters was evaluated, and seven mixed culture with the minimal relationship were selected. Actinomycetes were mostly identified as members of Streptomyces genus. These native streptomycetes present ability to grow as microbial consortia and to remove MTX. Indigenous actinomycetes consortia could be a promising tool for MTX biodegradation.