Methoxychlor bioremediation by defined consortium of environmental Streptomyces strains

Abstract

Methoxychlor is an organochlorine pesticide used worldwide against several insect pests, resulting in human exposure. This pesticide mimics endocrine hormone functions, interfering with normal endocrine activity in humans and wildlife. For this reason, it is imperative to develop methods to remove this pesticide from the environment, and though, bioremediation using microorganisms results as an excellent strategy. Five Streptomyces spp. strains previously isolated from organochlorine-polluted sites and capable to grow and remove methoxychlor were combined as different mixed cultures to increase methoxychlor removal. From the 39 consortia tested, one consortium (Streptomyces spp. A6, A12, A14, M7) was selected because of its high pesticide removal and specific dechlorinase activity to be assayed on slurry and soil systems. This consortium showed higher biomass values (8.3 9 106 ± 5.7 9 105 CFU mL-1) and methoxychlor removal (56.2 ± 2.3 %) on enriched slurry than in nonenriched slurry (7.3 9 105 ± 1.2 9 105 CFU mL-1 and 45.6 ± 7.4 % of pesticide removal). In soil systems, Streptomyces consortium showed higher growth (1.0 9 1011 ± 5.0 9 1010 CFU g-1) than in enriched slurry, although differences in methoxychlor removal between both culture conditions were not statistically significant. Therefore, the selected Streptomyces consortium may be suitable for the development of in situ (soil) and ex situ (slurry bioreactor) bioremediation methods because of their potential to remove methoxychlor from different systems.