Membrane toxicity of linear alcohol ethoxylates

Abstract

Abstract-The membrane toxicity of linear alcohol ethoxylates (AEO/single reference compounds and technical mixtures) was investigated with an in vitro method based on time-resolved spectroscopy on energy-transducing membranes. The nonspecific membrane perturbation of narcotic chemicals can be quantified by the degree of disturbance of buildup and relaxation of the membrane potential in membrane preparations of the purple bacterium Rhodobacter sphaeroides. The effect concentrations obtained for this narcotic effect correlated well with the results from various toxicity tests on whole organisms. In addition, the effect concentrations at the target site, the biological membrane, were derived from the nominal effect concentrations using membranewater partition coefficients. The test set of linear AEO comprised compounds with an alkyl chain length of 8 to 16 carbon units and 5 to 14 ethoxylate (EO) units covering more than four orders of magnitude of hydrophobicity (expressed as octanol-water partition coefficient). All AEO exhibited their toxic effect at concentrations well below the critical micelle concentration. When comparing aqueous effect concentrations, toxicity increased strongly with increasing length of the alkyl chain and showed a small parabolic dependence on the number of EO units with a maximum at eight EO units. With the toxic effect expressed in terms of membrane concentrations, all AEO exhibited similar activity in the concentration range typical for narcotic chemicals. The toxic membrane concentrations of AEO with 5 and Ն8 EO units were 200 and 60 mmol/kg lipid, which correspond to the critical body residues of nonpolar and polar narcotics in fish, respectively. In addition, the toxic effects of mixtures of AEO were measured and could be modeled as the sum of activities of the single constituents, confirming the concept of concentration additivity of compounds with the same mode of toxic action.

Toxic Effects of Linear Alkylbenzene Sulfonate on Metabolic Activity, Growth Rate, and Microcolony Formation ofNitrosomonasandNitrosospiraStrains

“…The cell membranes of AOB do not seem to be fundamentally different from those of many other gram-negative bacteria; the lipid composition is quite similar (55,62), and even if AOB have a larger specific membrane area than most other bacteria (51), it is difficult to see how this could contribute to their greater sensitivity to LAS. However, monomers of LAS and other surfactants are known to increase the permeability of biological membranes (13,14,43,64), and this could lead to uncoupling reactions during energy metabolism. Due to the low energy yield from NH 4 ϩ oxidation (8,34) and the high energy requirement for CO 2 fixation (34,35), it is likely that AOB are particularly sensitive to such uncoupling surfactants.…”

“…However, due to the difficulties involved in cultivation of AOB, there is still a general lack of data concerning the effects of toxic chemicals on the general physiology of these bacteria. Previous studies have dealt mostly with specific nitrification inhibitors targeting the NH 4 ϩ monooxygenase enzyme (5, 42), and very little is known about other targets of toxicants in AOB cells.Xenobiotic surfactants comprise a very important group of potentially toxic compounds that are believed to be harmful due to disruption of the function and structure of bacterial membranes (11,13,14,43,64). The linear alkylbenzene sulfonates (LAS) constitute the quantitatively most important group of synthetic surfactants used today, and the use of these compounds will likely increase in the years to come (12).…”

“…Xenobiotic surfactants comprise a very important group of potentially toxic compounds that are believed to be harmful due to disruption of the function and structure of bacterial membranes (11,13,14,43,64). The linear alkylbenzene sulfonates (LAS) constitute the quantitatively most important group of synthetic surfactants used today, and the use of these compounds will likely increase in the years to come (12).…”

Synergistic cytotoxic effect of tetrachlorocatechol and sodium azide in Escherichia coli: Toxicity, metabolism, and mechanistic aspects

“…Chem. 28, 2009 1381 their rapid growth rate is useful for studying toxicity effects over several generations in a short time period [20,21]. Our results revealed that NaN 3 enhanced the toxicity of the metabolites TCHQ and TCC.…”

Response of Workers to Polyoxyethylene Tridecyl Ether Surfactants in Relation to Hydrophilic-lipophilic Balance

“…Although the mode of action of surfactants against insects remains unknown, the interaction with biological membranes is believed to be an explanation [26,27]. Nonionic surfactants can also interfere with enzyme activity by binding with proteins.…”