engleski

Biotransformation activities of methanotrophic-heterotrophic groundwater community

This research focuses on the study of biotransformation activities of methanotrophic-heterotrophic groundwater community towards linear alkylbenzenesulphonates (LAS), complex molecules containing C_9-C_14 alkyl side-chain and the sulphonated aromatic ring, both structures related to the substances which are oxidized by methanotrophs. The main objective was to elucidate the potential role of ubiquitous methanotrophic bacteria in transformations of substances which are not their growth substrates, particularly multi-carbon compounds. The experiments were performed in batch culture (shake flasks) under the conditions favouring the growth of methanotrophic species and promoting the expression of soluble methane monooxygenase (i.e. by the addition of methane as only carbon source and using the nitrate mineral salts medium without copper). When growing under different methane and oxygen tensions, the methanotrophic-heterotrophic community was a stable association, consisting of one obligate methanotroph type II (CSC1) as dominant strain and four heterotrophs of different morphological and metabolic capabilities. Besides the capability of cometabolic transformation of trichloroethylene (Henry and Grbić-Galić, 1991) and chlorinated biphenyls (Adriaens and Grbić-Galić, 1994), the community revealed the capability to transform commercial LAS and pure 2C9LAS and 2C10LAS congeners. Although the mechanism of LAS transformation by methanotrophs still needs to be elucidated, simultaneous methane oxidation and LAS disappearance, with observed mutual competitive inhibition, support the hypothesis that the strain CSC1 may be involved in the oxidation of complex LAS molecules. This hypothesis is further supported by the fact that none of the four heterotrophic members revealed LAS transformation activity. Faster LAS transformation by the community than by the methanotrophic member illustrates the role and importance of methanotrophic-heterotrophic interactions in cometabolic transformation of complex LAS molecules.

biotransformation; methanotrophic-heterotrophic community

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