title: Novel alkylsulfatases required for biodegradation of the branched primary alkyl sulfate surfactant 2-butyloctyl sulfate.
abstract: 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.
authors.affiliation: School of Biosciences, Cardiff University, Cardiff CF10 3US. SEAC Environment Centre, Unilever Research Port Sunlight, Bebington, Wirral, Merseyside L63 3JW, United Kingdom.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ellis
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Hales
authors.forename: Naheed G A
authors.initials: NG
authors.lastname: Ur-Rehman
authors.forename: Graham F
authors.initials: GF
authors.lastname: White
mesh_terms: D001673:Biodegradation, Environmental; D003470:Culture Media; D011549:Pseudomonas / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification; D012722:Sewage / Q000382:microbiology; D013379:Substrate Specificity; D013429:Sulfatases / Q000378:metabolism*; D013463:Sulfuric Acid Esters / Q000378:metabolism*; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003470:Culture Media; D012722:Sewage; D013463:Sulfuric Acid Esters; D013501:Surface-Active Agents; D013429:Sulfatases; C019244:alkylsulfatase