BIODEGRADATION OF LINEAR ALKYLBENZENESULPHONATES (LAS) BY MIXED METHANOTROPHIC-HETEROTROPHIC CULTURES

The biodegradation of undecylbenzenesulphonate (C(11)LAS) was studied in shake flasks at 21 degrees C using two mixed bacterial cultures. Th e first culture, MM1, contained a type II methanotroph and four hetero trophs, and was enriched from a groundwater aquifer. The second cultur e, MC, consisted of five heterotrophic strains, most of them belonging to the genus Pseudomonas, and was isolated from the wastewater of a d etergent plant. Methane, carbon dioxide and oxygen concentrations were determined by gas chromatography. Concentrations of C,,LAS and the ar omatic intermediates were determined by reversed-phase HPLC. In spite of faster transformation of the alkyl side-chain by the culture MC, th e culture MM1 containing type II methanotroph was capable of further d egradation of C(11)LAS aromatic intermediates (sulphophenylalkanoates) . The most probable mechanism for the degradation of the alkyl part of the C(11)LAS molecule by both cultures was omega-oxidation of the ter minal methyl group followed by beta-oxidation. Studies of methane util ization demonstrated an approximately three times higher second-order rate coefficient for methane consumption (k(max)/K-s) in the absence o f C(11)LAS. This indicates a possible metabolic activity of methanotro phs in the transformation of the complex LAS molecule due to the metha ne monooxygenase enzyme system.