Enzymatic conjugation-deconjugation processes could accelerate the leaching of hydrophobic plastic additives

The leaching of plastic additives is fundamental to assessing their environmental risk, yet the role of biofilm-mediated biotransformation in this process remains poorly understood. This study investigates the influence of enzymatic conjugation (glucuronidation) on the leaching kinetics of UV stabilizers from low-density polyethylene (LDPE) fibers. By combining leaching experiments with a kinetic model, we identified distinct acceleration mechanisms governed by additive hydrophobicity. For highly hydrophobic benzotriazoles (UV-327 and UV-328), glucuronidation enhanced leaching by 20-28% relative to controls by accelerating mass transfer across the aqueous boundary layer (ABL). For moderately hydrophobic benzophenone-3 (BP-3), leaching increased by 289% as enzymatic activity sustained the concentration gradient by acting as a bulk-phase sink. These results demonstrate that enzymatic conjugation-deconjugation processes can substantially enhance the release of hydrophobic additives. As a result, abiotic models may underestimate the leaching of plastic-associated chemicals in biologically active environments.