Initial Stages in the Biodegradation of the Surfactant Sodium Dodecyltriethoxy Sulfate by Pseudomonas sp. Strain DES1

Abstract

The biodegradation of the surfactant sodium dodecyltriethoxy sulfate by Pseudomonas sp., strain DES1 (isolated from activated sludge plant effluent) has been studied. Growth of the organism when the S-labeled surfactant was present as the sole source of carbon and energy led to the appearance in the culture fluid of five S-labeled organic metabolites. These have been identified as mono-, di-, and triethylene glycol monosulfates (major metabolites) and acetic acid 2-(ethoxy sulfate) and acetic acid 2-(diethoxy sulfate), authentic samples of which have been prepared and characterized. Evidence is presented that the major metabolites were produced by rupture of one or another of the three ether linkages present in the surfactant molecule, probably via the agency of a single etherase enzyme. Acetic acid 2-(ethoxy sulfate) and acetic acid 2-(diethoxy sulfate) were formed by the oxidation of the free alcohol groups of di- and triethylene glycol monosulfates, respectively, and increased in amount during the stationary phase of growth. Inorganic S-sulfate also appeared in significant quantities in culture fluids and arose from the parent surfactant (presumably via the action of an alkylsulfatase) and not from any of the five metabolites. The appearance of sulfated organic metabolites during the exponential phase of growth and their quantitative relationship remained remarkably constant, even when additional carbon and energy sources (succinate or yeast extract) were also present in the growth media.