Abstract :
Biodegradation of undecylbenzenesulphonate (C11LAS) was performed in shake flasks at 21°C by using a mixed methanotrophic-heterotrophic culture containing type II methanotrophs. Concentrations of C11LAS and aromatic intermediates were determined by reversed-phase high-performance liquid chromatography (RP-HPLC). Methane and carbon dioxide concentrations were measured in headspace samples by using gas chromatography. RP-HPLC analyses of aqueous samples show that the culture MM1 expresses the capability of C11LAS transformation in the presence or absence of methane. Simultaneous methane oxidation and C11LAS degradation, and the inhibition of both transformation processes by acetylene were observed. This suggests the possibility that C11LAS transformation is catalyzed by methane monooxygenase (MMO). Comparable affinity of culture MM1 for both methane and C11LAS (Ks = 4•7 and 5•7 μM, respectively), and more than four times higher maximum transformation rate for methane than for C11LAS (k = 0•42 and 0•096 mg mg−1 (dry weight) cells day−1, respectively), were determined. This further supports the involvement of MMO enzyme system in transformation and suggests a pronounced competitive inhibition of C11LAS degradation by methane.
