Biodegradation pathways of phthalate esters by Mycolicibacterium parafortuitum J101 and its ability to enhance bioremediation

Phthalate esters (PAEs) are recalcitrant pollutants commonly used as plasticizers, and their degradation most effectively occurs by microorganisms. However, specific aspects of the degradation mechanism, particularly enzyme specificity and catalytic processes in the upper degradation pathway, remain unclear. Additionally, genes encoding esterases responsible for initial PAE hydrolysis have not been conclusively identified in many bacterial genera. In this study, Mycolicibacterium parafortuitum strain J101 was found to be capable of efficiently degrading and mineralizing three PAEs at an initial concentration of 100 mg/L in 7 days: short-chain dimethyl phthalate (88.57 %), diethyl phthalate (96.83 %), and dibutyl phthalate (99.37 %). Environmental conditions such as a pH less than 6 and greater than 5 % salinity affect the PAE degradation efficiency of strain J101. Genome mining revealed genes potentially involved in the complete degradation of PAEs by J101, which corresponds with J101's observed metabolic activity and gene expression. The cut0019 gene encodes a cutinase enzyme that is capable of hydrolyzing PAEs for initial degradation in the upper pathway. PAEs are transformed to phthalic acid, subsequently converted to protocatechuate and ultimately transformed to CO₂ and H₂O. A microcosm study revealed that the introduction of strain J101 significantly enhanced the efficiency of the degradation of mixed PAEs, and the strain synergized with indigenous microorganisms. Furthermore, the addition of strain J101 in landfill soil increased the diversity and complexity of interactions within the landfill soil bacterial community. Consequently, strain J101 demonstrates significant potential for application in the bioremediation of PAE-polluted environments.