Recent reports show that contrary to common perception, branched alkyl sulfate surfactants are readily biodegradable in standard biodegradability tests. We report here the isolation of bacteria capable of biodegrading 2-butyloctyl sulfate and the identification of novel enzymes that initiate the process. Enrichment culturing from activated sewage sludge yielded several strains capable of growth on 2-butyloctyl sulfate. Of these, two were selected for further study and identified as members of the genus Pseudomonas. Strain AE-A was able to utilize either sodium dodecyl sulfate (SDS) or 2-butyloctyl sulfate as a carbon and energy source for growth, but strain AE-D utilized only the latter. Depending on growth conditions, strain AE-A produced up to three alkylsulfatases, as shown by polyacrylamide gel electrophoresis zymography. Growth on either SDS or 2-butyloctyl sulfate or in nutrient broth produced an apparently constitutive, nonspecific primary alkylsulfatase, AP1, weakly active on SDS and on 2-butyloctyl sulfate. Growth on 2-butyloctyl sulfate produced a second enzyme, AP2, active on 2-butyloctyl sulfate but not on SDS, and growth on SDS produced a third enzyme, AP3, active on SDS but not on 2-butyloctyl sulfate. In contrast, strain AE-D, when grown on 2-butyloctyl sulfate (no growth on SDS), produced a single enzyme, DP1, active on 2-butyloctyl sulfate but not on SDS. DP1 was not produced in broth cultures. DP1 was induced when residual 2-butyloctyl sulfate was present in the growth medium, but the enzyme disappeared when the substrate was exhausted. Gas chromatographic analysis of products of incubating 2-butyloctyl sulfate with DP1 in gels revealed the formation of 2-butyloctanol, showing the enzyme to be a true sulfatase. In contrast, Pseudomonas sp. strain C12B, well known for its ability to degrade linear SDS, was unable to grow on 2-butyloctyl sulfate, and its alkylsulfatases responsible for initiating the degradation of SDS by releasing the parent alcohol exhibited no hydrolytic activity on 2-butyloctyl sulfate. DP1 and the analogous AP2 are thus new alkylsulfatase enzymes with novel specificity toward 2-butyloctyl sulfate.Synthetic surfactants are components of a variety of household and industrial detergent formulations. Other industrial applications include paints, textiles and fabrics, oil-spill dispersants, concrete, paper, lubricants, and many others (14,15,26). In 1990, world production of synthetic surfactants was 7 megatonnes (Mt) per annum, of which 5.3 Mt came from the United States, the European Union, and Japan (12). Of this part, 1.74 Mt per annum was anionic surfactant, a significant quantity which reflects the high demand for this type of surfactant. The anionic surfactant group embraces a range of compounds distinguished on the basis of chemical structure and includes primary alkyl sulfates, such as sodium dodecyl sulfate (SDS), and linear secondary alkyl sulfates, such as dodecyl 2-sulfate. Synthetic primary alkyl sulfates are based on feedstocks derived from long-chain olefins by us...

A range of Organisation for Economic Cooperation and Development (OECD) guideline test systems was used to determine the extent and possible mechanisms of biodegradation of dialkyl sulphosuccinate (DASS, C6/C8). Primary biodegradation of DASS was virtually complete in OECD guideline tests and in simulations of activated sludge sewage treatment systems under both optimal and adverse conditions, and of an anaerobic digester. Ultimate biodegradation increased from about 50% in ready tests to 94% in more powerful inherent tests. [14C]DASS was used to determine the fate of the surfactant in activated sludge and in surface waters. Mechanistic studies were performed to ascertain the biodegradative pathway of [14C]DASS. A putative degradation pathway for DASS is proposed.

The bacterial biodegradation of a secondary sulphonate, sulphosuccinate, has been shown to occur by direct desulphonation. A bacterium, designated Pseudomonas sp. BSI, was isolated from activated sewage sludge, for its capacity to grow on sulphosuccinate as the sole source of carbon and energy. Cultures grown on sulphosuccinate were able to convert this substrate to sulphite which was subsequently oxidized rapidly to sulphate. The sequence of desulphonation and carbon-chain catabolism of sulphosuccinate was determined from measurements of the kinetics of sulphite and 14C0, release from specifically radiolabelled sulpho[l,4-14C]succinate and sulpho[2,3-1 4 C ]~~~~i n a t e , which were synthesized from the corresponding maleic anhydrides. When each radiolabelled compound was incubated separately with washed-cell suspensions of Pseudomonas BSI, sulphite was released before 14C02, as shown by chemical assay and radiorespirometry, respectively. Differences in the kinetics and extent of 14C02 release from the I,& and 2,3-labelled substrates were consistent with entry of the intact C4 chain into the citric acid cycle. When carrier oxaloacetate was added to incubation mixtures containing resting-cell suspensions and radiolabelled sulphosuccinate, a radiolabelled metabolite with the same HPLC retention time as oxaloacetate accumulated. No radioactive metabolites accumulated when carrier oxaloacetate was replaced with succinate, f umarate or malate. Collectively, the data indicated co-production of sulphite and oxaloacetate from sulphosuccinate, which is interpreted in terms of an oxidative desulphonation mechanism.

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 35S-labeled surfactant was present as the sole source of carbon and energy led to the appearance in the culture fluid of five 35S-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.

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