A novel PGPR Streptomyces sp. for efficient phthalate biodegradation: Mechanistic insights and application in...

Phthalate esters (PAEs) are ubiquitous emerging contaminants that pose significant risks to food safety due to their persistence and bioaccumulation in crops. In this study, a PAE-degrading plant growth-promoting rhizobacterium (PGPR), Streptomyces sp. RS09, was isolated from the rice rhizoplane. Strain RS09 efficiently utilized multiple PAEs as sole carbon and energy sources and exhibited robust degradation activity toward di(2-ethylhexyl) phthalate (DEHP) across a wide concentration range, following a first-order kinetic model. Metabolite profiling identified various monoesters and phthalate derivatives, allowing the reconstruction of two converging degradation pathways involving de-esterification, β-oxidation, and aromatic ring cleavage. Genome annotation revealed an abundance of catabolic genes related to ester hydrolysis and aromatic compound metabolism, which underpins its broad substrate adaptability. Soil inoculation with RS09 significantly accelerated DEHP degradation and markedly reduced DEHP accumulation in rice tissues. These results demonstrate that Streptomyces sp. RS09 is a rhizosphere-derived strain with dual capabilities in PAE biodegradation and plant growth promotion, highlighting its potential as a promising microbial resource for mitigating PAE contamination in agricultural environments. This study offers a mechanistically informed strategy for the sustainable remediation of PAE-contaminated agroecosystems.