AEROBIC TRANSFORMATION OF LINEAR ALKYLBENZENESULPHONATES BY MIXED METHANE-UTILIZING BACTERIA

Biodegradation of commercial linear alkylbenzene-sulphonate (LAS) was performed in shake flasks in the presence and absence of methane as a primary growth substrate for methanotrophs and as an inducer for catab olic enzymes. Methane-utilizing culture MM1 was dominated by type II m ethanotrophs and originated from a groundwater aquifer. Methane, carbo n dioxide, and oxygen concentrations were measured by using gas chroma tography. Disappearance of LAS, a mixture of C-10-C-13 homologues, was monitored by reversed-phase high-performance liquid chromatography (R P-HPLC). Methane reduced LAS transformation rate in a concentration de pendent manner, suggesting competitive inhibition between natural subs trate, methane, and fortuitous substrate, LAS. The fastest LAS transfo rmation was determined in the absence of methane. Simultaneous methane oxidation and LAS degradation, and the inhibition of both transformat ion processes by acetylene, indicated the involvement of a methane-mon ooxygenase enzyme system in LAS transformation. RP-HPLC analysis showe d that culture MM1 exhibited preferential capability to transform LAS with longer alkyl side-chain. Consequently, the highest transformation rate was observed with the homologue of C-13 LAS.