RESUMO
The possibility of complete degradation of DDT by Pseudomonas aeruginosa 640x was demonstrated in principle. A study of the conditions of degradation of DDT by this culture was made. It was demonstrated that only dechlorination of DDT to DDD is accomplished without addition of a supplementary substrate. The rest of the processes right up to the formation of benzhydrol and phenylacetic acid take place only under conditions of cometabolism. For dechlorination of the aliphatic fragment of DDT and the aromatic rings, anaerobic conditions, nitrates in the form of electron acceptors, and calcium lactate as a cosubstrate are preferred. Degradation of nonchlorinated benzophenone takes place only under aerobic conditions with glycerol as a cosubstrate. Phenylacetic acid and benzhydrol are used by the culture as sole sources of carbon; aerobic conditions are necessary for their degradation. On the basis of analysis of decomposition products of DDT and a study of the pathways of degradation of its metabolites and analogs, a means of converting DDT by P. aeruginosa 640x is proposed.
Assuntos
DDT/metabolismo , Pseudomonas aeruginosa/metabolismo , Compostos Benzidrílicos/metabolismo , Meios de Cultura , Diclorodifenildicloroetano/metabolismo , Nitratos , Oxigênio , Fenilacetatos/metabolismoRESUMO
A search was made for active cultures that break down DDT. More than 600 microorganisms were isolated from soils treated for a long time with DDT and from accumulating cultures with DDT or its analogs as the carbon source and with DDT or its analogs and supplementary carbon sources. Cultures capable of degrading DDT under conditions of cometabolism were found among them. It was shown that the dechlorination of the trichloromethyl group of DDT was accomplished by a large number of microorganisms and occurred primarily under conditions of limited aeration. The elimination of chloride ions from the aromatic rings occurred only in the presence of cosubstrates under aerobic conditions and only with two strains. The strain Nocardia sp. 306x carried out complete degradation of DDT with the formation of DBH, DCBP, and an as yet unidentified entirely dechlorinated product. The most profound decomposition of DDT was produced by a culture of Ps. aeruginosa 640x, which entirely degraded the DDT molecule with the formation of phenylacetic acid.
