Biodegradation of phthalic acid esters by a novel marine bacterial strain RL-BY03: Characterization, metabolic pathway, bioaugmentation and genome analysis

Biodegradation is recognized as the main route for the decomposition of phthalic acid esters (PAEs) in nature, but the fate of PAEs in marine ecosystems is not well understood. Herein, a novel marine bacterium, Gordonia sihwaniensis RL-BY03, was identified and analyzed for its ability to degrade PAEs. Furthermore, the metabolic mechanism of di-(2-ethylhexyl) phthalate (DEHP) was examined through UPLC-MS/MS and genomic analysis. RL-BY03 could rely solely on several types of PAEs as its sole carbon source. Initial pH and temperature for DEHP degradation were optimized as 8.0 and 30 °C, respectively. Surprisingly, RL-BY03 could simultaneously degrade ethyl acetate and DEHP and they could increase the cell surface hydrophobicity. DEHP degradation kinetics fitted well with the first-order decay model. The metabolic pathway of DEHP was deduced following the detection of five metabolic intermediates. Further, genes that are related to DEHP degradation were identified through genomic analysis and their expression levels were validated through RT-qPCR. A co-related metabolic pathway at biochemical and molecular level indicated that DEHP was turned into DBP and DEP by β-oxidation, which was further hydrolyzed into phthalic acid. Phthalic acid was utilized through catechol branch of β-ketoadipate pathway. Additionally, RL-BY03 exhibited excellent bioremediation potential for DEHP-contaminated marine samples. In general, these findings have the potential to enhance our understanding of the fate of PAEs in marine ecosystems.