Isolation and Characterization of An Endosulfan-Degrading Strain, Stenotrophomonas sp. LD-6, and its Potential in Soil Bioremediation

Aerobic bacteria degrading endosulfan were isolated from contaminated sludge. One of the isolates, LD-6, was identified as Stenotrophomonas sp. The bacterium could utilize endosulfan as the sole source of carbon and sulfur. 100 mg/l endosulfan was completely degraded within 10 days, and endosulfan diol and endosulfan ether were detected as major metabolites with a slight decrease in culture pH. The results indicated that Stenotrophomonas. sp. LD-6 might degrade endosulfan by a non-oxidative pathway. Biodegradation of both isomers was relatively better at a temperature range of 25-35 degrees C, with a maximum at 30 degrees C. In addition, cell crude extract of strain LD-6 could metabolize endosulfan rapidly, and degradative enzymes were intracellular distributed and constitutively expressed. Besides, application of the strain was found to promote the removal of endosulfan in soil. This study might help with the future research in better understanding of the biodegradation.

DISSIPAÇÃO DE ENDOSSULFAN EM AMOSTRAS DE DOIS TIPOS DE SOLOS BRASILEIROS TRATADAS EM LABORATÓRIO

Avaliou-se a persistência e a degradação de Endossulfan em gleissolo húmico (GH) e argissolo vermelho-amarelo (AA), com diferentes características químicas e físicas, tratados em laboratório com solução de 14C-endossulfan. Determinou-se a persistência a partir da produção de 14CO2 aos 7, 14, 21 e 28 dias após o tratamento. A degradação foi avaliada aos 0, 30, 60 e 90 dias após o tratamento pela extração das amostras, análise dos extratos e combustão das amostras extraídas. O radiocarbono presente (extraível e ligado) foi quantificado por espectrometria de cintilação em líquido. Alíquotas dos extratos foram analisadas por cromatografia em camada delgada (CCD) quanto à presença de produtos de degradação. Nos dois tipos de solo, a persistência ambiental e o padrão de degradação mostraram-e semelhantes. Os valores detectados para a produção de 14CO2, em ambos os tipos de solo, evidenciaram meia-vida entre 90 e 180 dias. Ocorreu diminuição na recuperação de 14C-resíduos extraíveis e aumento de 14C-resíduos ligados aos 0, 30, 60 e 90 dias, sendo a porcentagem desses últimos maior no solo GH (cerca de 8 %) do que no solo AA (cerca de 6%). A CCD revelou nos dois tipos de solos a presença dos produtos de degradação endossulfan-diol, logo após o tratamento, endossulfan-sulfato e outro nãoidentificado aos 30, 60 e 90 dias, provavelmente relacionados com a sua biodegradação. ENDOSULFAN DISSIPATION IN TWO BRAZILIAN SOIL SAMPLES TREATED IN LABORATORY Abstract Persistant and degradation of Endosulfan in different soils (GH and AA) with distinct chemical and physical characteristics were evaluated by treatment with 14C-endosulfan solution. Persistance was determined from the production of 14CO2, 7, 14, 21 and 28 days after treatment. Degradation was evaluated at 0, 30, 60 and 90 days after treatment by sample extraction, extract analysis and combustion of extracted samples. The radiocarbon (extractable and bound) was quantified by cintilation spectroscopy. Aliquots of the extracts were analysed by thyn layer chromatography (TLC) for the presence of degradation products. In both soil samples, environmental persistance and degradation standard were similar. The values detected for the production of 14CO2 in both soils evidenced half-life between 90 and 180 days. Reduction in the recuperation of 14C- extractable residues occured and augmented for bound 14C residues at 0, 30, 60 and 90 days, being the latter percentage higher in GH soil (around 8%) than in AA soil (around 6%). TLC showed in both soils the presence of endosulfan-diol degradation products right after the treatment, endosulfan-sulphate and other non identified at 30, 60 and 90 days, probably related with its biodegradation.