ORGANOCHLORINE PESTICIDES BIODEGRADATION BY INDIGENOUS ACTINOMYCETES STRAINS

BENIMELI, C.S.; FUENTES, M.S.; SÁEZ, J.M.; BOURGUIGNON, N.; CUOZZO, S.A. ; AMOROSO, M.J.

Pucón

Workshop; 2nd Internacional Workshop Advances in Science and Technology of natural Resources; 2010

Universidad de la Frontera

Organochlorine pesticides (OPs) have been extensively used to protect and improve quality and quantity of food commodities, building materials, clothing, animal health, and to combat certain diseases transmitted by insect vectors to man and animals. However, indiscriminate use of pesticides has caused serious concern about toxic effects by residues on non-target organisms. The g-HCH is an organochlorine pesticide used in agriculture and medicine to world level. It has a big tendency to bioaccumulate into the environment. There are many reports indicating that hexachlorocyclohexane (g-HCH) is present in soil, water, air, plants, agricultural products, animals, food, microbial environments etc. Considered a potential carcinogen and listed as a priority pollutant by the US EPA, g-HCH is a lipophilic compound and therefore tends to accumulate and concentrate in the body fats of animals and humans. In Salí River, the main hydrographic system of Tucumán, Argentina, lindane was detected 10-fold in relation to the traces permitted concentrations. Hence the development of new technologies to remediate these sites using microorganisms is every time more necessary. The actinomycetes are Gram positive bacteria with great potential to bioremediate xenobiotics. One strain, Streptomyces sp M7, isolated from organochlorine pesticides contaminated sediment was selected for its capacity to grow in the presence of lindane as only carbon source. This microorganism was cultured in soil extract medium added of lindane 100 mg L-1, obtaining a maximal growth of 0.065 mg mL-1, similar to the control, with a highest lindane removal of 70.4% at 30 ºC and pH 7. When different initial pesticide concentrations (100, 150, 200 and 300 mg L-1) were added in soil medium, an increment of the microbial growth was detected in all the concentrations tested. Also a diminution of the residual lindane concentration was determined in the soil samples in relation to the abiotic controls (29.1; 78.03; 38.81 and 14.42% respectively). Besides it was determined the optimum Streptomyces sp. M7 inoculum when lindane 100 mg Kg-1soil was added to the soil sample. It was 2 g Kg-1soil for obtaining the most efficiently bioremediation process, the lindane removal in these conditions was 67.8% at 28 days of incubation. Later it was considered necessary to know the pesticide effects on maize plants seeded in lindane-contaminated soil previously inoculated with Streptomyces sp. M7. Lindane concentrations of 100, 200, and 400 mg kg-1 soil did not affect the germination and vigor index of maize plants seeded in contaminated soils without Streptomyces sp. M7. When this microorganism was inoculated at the same conditions a better vigor index was observed and 68% of lindane was removed. These results confirm the potential lindane-contaminated soil bioremediation of Streptomyces sp. M7.