Enrichment of linear alkylbenzenesulphonate (LAS) degrading bacteria in continuous culture

Absract Enrichment experiments were carried out in continuous‐flow units using a mineral medium with commercial linear alkylbenzenesulphonate (LAS) as the limiting carbon‐ and energy‐source. The mixed bacterial culture originating from the waste water of a detergent plant consisted of five strains belonging to the genus Pseudomonas and two strains each of the genera Achromobacter and Acinetobacter. The cultivation conditions corresponding to dilution rates of 0.025‐0.1 h ‐1 and LAS concentrations of 20–50 mg/1 were examined. During the experiments the composition of mixed cultures and the kinetics of LAS biodegradation were followed. Continuous‐flow enrichment experiments resulted in the selection of six bacterial cultures with different compositions of individual species and capability to utilize LAS. From the original seven strains at lower dilution rates (0.025 and 0.05 h ‐1 ) six were selected, excluding Pseudomonas sp. 3, while at the highest dilution rate (0.1/h ‐1 ) five strains were selected after eliminating Pseudomonas sp. 5 and Achromobacter sp. 1. All enriched mixed cultures were more efficient in primary than in ultimate LAS degradation. Two of the culture strains were able to achieve primary LAS degradation ( Pseudomonas sp. 1 in mineral medium with LAS as the sole carbon‐ and energy‐source and Acinetobacter sp. 3 in medium supplemented by yeast extract and nutrient broth). None of the strains could degrade LAS completely, which indicates that many types of interactions based on combined metabolic attack as well as those based on provision of specific nutrients, may exist between culture members during the complete LAS bio‐oxidation.