BIODEGRADATION OF UNDECYLBENZENESULPHONATE BY MIXED METHANE-OXIDIZINGCULTURE

Biodegradation of undecylbenzenesulphonate (C(11)LAS) was performed in shake flasks at 21 degrees C by using a mixed methanotrophic-heterotr ophic 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 dioxi de concentrations were measured in headspace samples by using gas chro matography. RP-HPLC analyses of aqueous samples show that the culture MM1 expresses the capability of C(11)LAS transformation in the presenc e or absence of methane. Simultaneous methane oxidation and C(11)LAS d egradation, and the inhibition of both transformation processes by ace tylene were observed. This suggests the possibility that C(11)LAS tran sformation is catalyzed by methane monooxygenase (MMO). Comparable aff inity 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 transform ation 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 fur ther, supports the involvement of MMO enzyme system in transformation and suggests a pronounced competitive inhibition of C(11)LAS degradati on by methane.