RESUMO
Sulfentrazone is amongst the most widely used herbicides for treating the main crops in the State of São Paulo, Brazil, but few studies are available on the biotransformation of this compound in Brazilian soils. Soil samples of Rhodic Hapludox soil were supplemented with sulfentrazone (0.7 µg active ingredient (a.i.) g-1 soil) and maintained at 27ºC. The soil moisture content was corrected to 30, 70 or 100 % water holding capacity (WHC) and maintained constant until the end of the experimental period. Herbicide-free soil samples were used as controls. Another experiment was carried out using soil samples maintained at a constant moisture content of 70% WHC, supplemented or otherwise with the herbicide, and submitted to different temperatures of 15, 30 and 40º C. In both experiments, aliquots were removed after various incubation periods for the quantitative analysis of sulfentrazone residues by gas chromatography. Herbicide-degrading microorganisms were isolated and identified. After 120 days a significant effect on herbicide degradation was observed for the factor of temperature, degradation being higher at 30 and 40º C. A half-life of 91.6 days was estimated at 27º C and 70 % WHC. The soil moisture content did not significantly affect sulfentrazone degradation and the microorganisms identified as potential sulfentrazone degraders were Nocardia brasiliensis and Penicillium sp. The present study enhanced the prospects for future studies on the bio-prospecting for microbial populations related to the degradation of sulfentrazone, and may also contribute to the development of strategies for the bioremediation of sulfentrazone-polluted soils.
RESUMO
Terminal Restriction Fragment Length Polymorphism (T-RFLP) is a culture-independent fingerprinting method for microbial community analysis. Profiles generated by an automated electrophoresis system can be analysed quantitatively using either peak height or peak area data. Statistical testing demontrated that peak height data showed to be more reproducible than peak area data.
Terminal Restriction Fragment Length Polymorphism (T-RFLP) é um método molecular, independente de cultivo, para análise de comunidades microbianas. Perfis gerados por um sistema automatizado de eletroforese podem ser analisados quantitativamente usando dados de altura ou área dos picos. Os dados de altura mostraram-se mais reprodutíveis do que os de área.
RESUMO
Thirteen deuteromycete ligninolytic fungal strains were grown in media containing polycyclic aromatic hydrocarbons (PAHs), for 6 and 10 days. The PAHs were added directly with the inocula or on the third day of cultivation. A selection of the best strains was carried out based on the levels of degradation of the PAHs and also on the ligninolytic activities produced by the fungi. The selected strains were cultivated for 3, 6, 9, 12 and 15 days in the PAHs-containing media. Degradation of PAHs, as measured by reversed-phase HPLC on a C18 column, varied with each strain as did the ligninolytic enzymes present in the culture supernatants. Highest degradation of naphthalene (69%) was produced by the strain 984, having Mn-peroxidase activity, followed by strain 870 (17%) showing lignin peroxidase and laccase activities. The greatest degradation of phenanthrene (12%) was observed with strain 870 containing Mn-peroxidase and laccase activities. When anthracene was used, the strain 710 produced a good level of degradation (65%).
Treze fungos deuteromicetos ligninolíticos foram cultivados em meio contendo hidrocarbonetos aromáticos policíclicos (HAPs) por 6 e 10 dias. Os HAPs foram adicionados diretamente com o inóculo ou no terceiro dia de cultivo. A seleção das melhores linhagens foi baseada nos níveis de degradação dos HAPs e também nas atividades ligninolíticas produzidas pelas linhagens fúngicas. Essas melhores linhagens foram então cultivadas por 3, 6, 9, 12 e 15 dias. A degradação dos HAPs foi monitorada por cromatografia líquida de alta eficiência (CLAE) em uma coluna C18, variando para cada linhagem assim como as enzimas ligninolíticas presentes nos sobrenadantes das culturas. Alta degradação de naftaleno (69%) foi obtida pela linhagem 984, tendo atividade de Mn-peroxidase, seguida pela linhagem 870 (17%) a qual apresentou atividades de lignina peroxidase e lacase. A melhor porcentagem de degradação de fenantreno (12%) foi observada pela linhagem 870 contendo atividades de Mn-peroxidase e lacase. Quando antraceno foi utilizado como fonte de carbono, a linhagem 710 apresentou nível de degradação de 65%.