Use of sodium dodecyl sulphate for stimulation of biodegradation of n-alkanes without residual contamination by the surfactant

The capacity of a range of aliphatic alkanes (C6–C16), intermediates of n-decane oxidation and sodium dodecyl sulphate (SDS) to induce decane-mineralization activity in the cells of Pseudomonas C12B was compared with that for n-decane. The comparison on quantitative basis had two serious limitations: low solubility of tested inducers in aqueous solutions and their toxicity to bacterial cells. Carbon chain length and the presence of hydroxyl group were the important factors for induction activity. However, presence of hydroxyl groups at both ends of alkyl chain prevented the induction of decane-mineralization activity. Good induction activity by SDS was caused either by the presence of free end of alkyl chain, or by bacterial hydrolysis of sulphate group to yield alcohol, which in turn served as true inducer. The presence of SDS in the culture medium with n-decane as main source of carbon and energy accelerated the growth of Pseudomonas C12B. SDS disappeared from the culture medium in early stages of cultivation suggesting preferential degradation by the bacterium, while the consumption of n-decane was accelerated. This may be associated with the capacity of SDS to induce decane-mineralization system in Pseudomonas C12B and/or with the ability of SDS to stimulate the surface attachment of competent bacteria resulting in the close proximity of the cells with alkane droplets, and thus, enhanced breakdown of the hydrocarbon pollutant.