Diverse metabolic pathways in the degradation of phenylalkanoic acids and their monohydroxylated derivatives in Cupriavidus sp. strain ST-14

Abstract Cupriavidus sp. strain ST-14 isolated from municipal waste-contaminated soil had previously been described to harbour catabolic potential of assimilating 2- and 4-nitrobenzoic acids. Apart from the mononitrobenzoic acids, strain ST-14 was observed to be capable of utilizing various phenylalkanoic acids singly, as sole carbon and energy sources. The results of chromatographic and spectrometric analyses in combination with oxygen uptake and enzyme activity studies, revealed the assimilation of phenylacetic acid via phenylacetyl CoA and 3-phenylpropionic acid via β-oxidation pathway with the formation of benzoic acid and catechol as metabolic intermediates. Additionally, all the isomers of monohydroxyphenylacetic acids were metabolized by the action of substrate-specific monooxygenases to furnish homogentisic acid, which was then assimilated via classical homogentisate metabolic pathway. On the other hand, 3-(3-hydroxyphenyl)propionic acid and 3-(4-hydroxyphenyl)propionic acid were metabolized via the formation of 3-(2,3-dihydroxyphenyl)propionic acid and 4-hydroxybenzoic acid, respectively, ultimately leading to the TCA cycle intermediates. The present study illustrates a broad degradative potential of strain ST-14, harbouring diverse catabolic machineries of biotechnological importance, elucidating couple of pathways, reported for the first time in the assimilation of hydroxyphenylalkanoic acids.