Complete degradation of butyl benzyl phthalate by a defined bacterial consortium: Role of individual isolates in the assimilation pathway

Abstract

Two bacterial strains, in consortium, were isolated by enrichment techniques from municipal waste-contaminated soil, which utilized butyl benzyl phthalate (BBP) as the sole carbon source. One of the isolates was identified as Arthrobacter sp. strain WY and the other one as Acinetobacter sp. strain FW based on the morphological, nutritional and biochemical characteristics and 16S rRNA sequence analysis. Various metabolites of BBP engendered by Arthrobacter sp. strain WY were isolated and identified by a combination of chromatographic and spectrophotometric analyses, which revealed a pathway involving monobutylphthalate (MBuP), monobenzyl phthalate (MBzP), phthalic acid and protocatechuic acid. The protocatechuic acid in turn was processed by ortho-cleavage dioxygenase to form β-carboxy-cis,cis-muconate, ultimately leading to the TCA cycle. The Arthrobacter sp. strain WY could not utilize the hydrolyzed alcohols of BBP. On the other hand, the Acinetobacter sp. strain FW, which by itself could not utilize BBP as the sole carbon source, is capable of utilizing the hydrolyzed alcohols of BBP. Benzyl alcohol was found to be metabolized by the Acinetobacter sp. strain FW via benzaldehyde, benzoic acid and catechol. Catechol was further degraded by ortho-cleavage dioxygenase to cis,cis-muconic acid and subsequently to muconolactone leading to β-ketoadipate pathway. Moreover, the Acinetobacter sp. strain FW metabolized 1-butanol through butyraldehyde and butyric acid leading to the tricarboxylic acid cycle via β-oxidation pathway. This is the first report on the complete degradation of BBP by a defined consortium describing the role of its individual constituents in the BBP assimilation pathway.