COMETABOLIC TRANSFORMATION OF LINEAR ALKYLBENZENESULPHONATES BY METHANOTROPHS

Cometabolic transformation of commercial linear alkylbenzenesulphonate s (LAS) and pure congeners of 2-[4-(sulphophenyl)]nonan (2C(9)LAS) and 2-[4-(sulphophenyl)]decan (2C(10)LAS) was studied by using a mixed me thanotrophic-heterotrophic culture MM1 and a pure culture of type II m ethanotroph (strain CSC1), isolated from culture MM1. Cultures were gr own in shake flasks under conditions promoting expression of the solub le methane monooxygenase (sMMO). Both the mixed culture MM1 and the pu re culture CSC1 were capable of transforming LAS with or without metha ne as the natural substrate. Experiments performed without methane (re sting cells) showed faster cometabolic transformation of LAS congeners with longer alkyl side-chains. Both 2C(9)LAS and 2C(10)LAS congeners were transformed significantly faster at 30 degrees C, although the op timum temperature for the growth of mixed culture MM1 was 20 degrees C . Simultaneous methane oxidation and LAS transformation, and their mut ual competitive inhibition, indicated the involvement of the MMO enzym e system and possible methanotrophic activity in the initiation of com etabolic LAS transformation. The capability of two heterotrophic speci es to transform sulphophenyldecanoic acid suggests possible heterotrop hic activity in further LAS transformation CII-oxidation). Faster LAS transformation by mixed culture MM1 than by pure culture CSC1 suggeste d that methanotrophic-hetero trophic interactions are important for tr ansformation of the complex LAS molecule. Copyright (C) 1996 Elsevier Science Ltd