BIODEGRADATION OF UNDECYLBENZENESULPHONATE BY MIXED METHANE-OXIDIZING CULTURE

Biodegradation of undecylbenzenesulphonate (C(11)LAS) was performed in shake flasks at 21 degrees C by using a mixed methanotrophic-heterotrophic culture containing type II methanotrophs. Concentrations of C(11)LAS 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 C(11)LAS transformation in the presence or absence of methane. Simultaneous methane oxidation and C(11)LAS degradation, and the inhibition of both transformation processes by acetylene were observed. This suggests the possibility that C(11)LAS transformation is catalyzed by methane monooxygenase (MMO). Comparable affinity of culture MM1 for both methane and C(11)LAS (K-s = 4.7 and 5.9 mu M, respectively), and more than four times higher maximum transformation rate for methane than for C(11)LAS (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 C(11)LAS degradation by methane.