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, 66 (5), 1911-6

An Alpha-Proteobacterium Converts Linear Alkylbenzenesulfonate Surfactants Into Sulfophenylcarboxylates and Linear Alkyldiphenyletherdisulfonate Surfactants Into Sulfodiphenylethercarboxylates

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An Alpha-Proteobacterium Converts Linear Alkylbenzenesulfonate Surfactants Into Sulfophenylcarboxylates and Linear Alkyldiphenyletherdisulfonate Surfactants Into Sulfodiphenylethercarboxylates

D Schleheck et al. Appl Environ Microbiol.

Abstract

The surfactant linear alkylbenzenesulfonate (LAS; 0.5 mM) or linear monoalkyldiphenyletherdisulfonate (LADPEDS; 0.5 mM) in salts medium was easily degraded in laboratory trickling filters, whereas carbon-limited, aerobic enrichment cultures in suspended culture with the same inocula did not grow. We took portions of the trickling filters which degraded LADPEDS, shook the organisms from the solid support (polyester), and found that growth in suspended culture in LADPEDS-salts medium occurred only in the presence of some solid support (polyester fleece or glass wool), though little biomass was immobilized on the support. The end products in suspended culture were identical with those from the trickling filters. There was low plating efficiency of LADPEDS-grown cultures on complex medium, and no picked colony or mixture of colonies grew in LADPEDS-salts-glass wool medium. However, selective plates containing LADPEDS-salts medium solidified with agarose yielded LADPEDS-dependent, pinpoint colonies which could be picked singly and subcultured in selective liquid medium. Isolate DS-1 was a bacterium which showed 93% sequence homology (16S ribosomal DNA) to its nearest phylogenetic neighbor, an alpha-proteobacterium. Strain DS-1 grew heterotrophically in LADPEDS-salts-glass wool medium and converted the set of aryl-substituted alkanes to the corresponding aryl-substituted carboxylic acids of shorter chain length. Similarly, strain DS-1 grew heterotrophically with commercial LAS, converting it to a set of sulfophenylcarboxylates. Growth with a single isomer of LAS [3-(4-sulfophenyl)dodecane] was concomitant with excretion of 4-(4-sulfophenyl)hexanoate, which was identified by matrix-assisted laser desorption ionization mass spectrometry. The growth yield (6.4 g of protein/mol of C) indicated mass balance, which, with the specific growth rate (0.05 h(-1)), indicated a specific utilization rate of LAS of 2.2 mkat/kg of protein.

Figures

FIG. 1
FIG. 1
A representative LAS congener with its conversion to a defined SPC and a hypothetical LADPEDS congener and with its presumed metabolism to a SDPEC. Commercial LAS always shows the subterminal substitution of the 4-sulfophenyl moiety; the chain length usually ranges from C10 to C13 (23). Commercial C16 LADPEDS always shows the subterminal substitution of the diphenylether. It thus has seven positional isomers on the alkyl chain, each of which has a chiral center. Ten combinations of the alkyl, sulfonate, and ether substituents on the first ring are possible, as are three positional isomers of sulfonation on the second ring. Although substituents are nominally LADPEDS, dialkylated species and monosulfonated ethers also occur (Dowfax surfactant reaction mixture, Dow product information 1510-017A, p. 1, 1997).
FIG. 2
FIG. 2
Primary degradation of commercial LADPEDS in a trickling filter as determined by HPLC. LADPEDS-salts medium (0.33 mM; upper chromatogram) was pumped onto the trickling filter, and the eluate in the steady state (lower chromatogram) contained largely peaks of shorter retention time. Inset, UV spectra of representative peaks of substrate (upper scan) and product (lower scan).
FIG. 3
FIG. 3
Growth of the mixed culture in 1 mM LADPEDS-salts-glass wool medium (●) and the specific activity of LADPEDS-dependent oxygen uptake during growth (▵). OD, optical density.
FIG. 4
FIG. 4
Heterotrophic growth of the mixed culture utilizing commercial LADPEDS in suspended culture, including data for LADPEDS (■), SDPEC (□), the ammonium ion (○), and the sum of nitrate and nitrite formed (●). OD, optical density.
FIG. 5
FIG. 5
Growth of α-proteobacterium strain DS-1 in 1.7 mM 3-C12-LAS–salts–glass wool medium (●) with concomitant quantitative formation of 4-C6-SPC (inset).

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