Biodegradation of Linear Alkylbenzenesulphonates (C11LAS) by Mixed Methanotrophic/Heterotrophic and Mixed Heterotrophic Bacterial Cultures
Dubravka Hršak, Dunja Grbić-Galić*
Center for Marine Research Zagreb, Rudjer Bošković Institute, POB 1016, 41001 Zagreb, Croatia
*Department of Civil Engineering, Stanford University, Stanford, CA 94305-4020, USA
Article history:
Received January 27, 1993
Accepted April 22, 1993
Summary:
The objective of our work was to evaluate whether mixed methanotrophic/heterotrophic cultures are capable to degrade linear alkylbenzenesulphonates (LAS) major surfactants used in household detergents and widespread pollutants in waste water and natural waters. Mixed bacterial culture (MM1) containing a type II methanotroph and four heterotrophic strains, originating from an uncontaminated groundwater aquifer and a mixed bacterial culture consisting of five heterotrophic strains, isolated from the waste water of a detergent plant were used. Biodegradation experiments were conducted in shake flasks at 21 °C. Methane, carbon dioxide and oxygen concentrations were determined by headspace analysis on a Fisher-Hamilton gas partitioner. Concentrations of C11LAS and their intermediates were measured by reversed-phase high-performance liquid chromatography (RP-HPLC). Comparison of the kinetic parameters shows that the mixed heterotrophic culture was more efficient in degradation of the alkyl chain than the mixed culture containing type II methanotroph. On the contrary, mixed culture MM1 was able to further the degradation of C11LAS breakdown intermediates (sulphophenylalcanoic acids), while mixed culture with only heterotrophic species did not express this capability under the same experimental conditions. Occurrence of the same intermediates and only C-odd sulphophenylalcanoic acids suggested that the most probable mechanism for the degradation of the alkyl part of LAS molecule by both mixed cultures was ω- and β-oxidation. The rate studies for methane utilization demonstrate competitive inhibition of methane oxidation in the presence of C11LAS.