Influence of polyvinyl chloride (PVC) microplastic morphology on bacterial survival during thermal and ultraviolet-C inactivation in aqueous systems.

Microplastics are increasingly detected in water and food-associated environments, yet how particle morphology influences microbial persistence during inactivation remains poorly understood. This study aims to develop polyvinyl chloride (PVC) microplastic particles with distinct morphologies and controlled size ranges, and to evaluate how particle morphology influences bacterial attachment and survival during thermal and ultraviolet-C (UVC) inactivation in aqueous systems. First, we developed a PVC microplastic model system with distinct morphologies and controlled size fractions. Original PVC particles were relatively smooth and rounded, whereas irregular particles were generated by compounding, pelletizing, and cryogenically grinding the same PVC material, followed by sieving into defined size ranges. Second, using this model system, we evaluated how PVC particle morphology affected bacterial attachment and survival during thermal and UVC inactivation in aqueous systems. Escherichia coli O157:H7 and Listeria innocua were used as model gram-negative and gram-positive bacteria. Confocal microscopy showed attachment of E. coli to both particle types, with stronger association on ground PVC particles. In the presence of PVC particles, thermal log reductions decreased to approximately 4.0-5.1 log CFUs/mL, compared with about 5.9 log CFU/mL in microplastic-free controls, while UVC log reductions decreased to about 3.9-4.6 log CFU/mL, compared with about 5.2-6.0 log CFU/mL in microplastic-free controls. Ground PVC provided greater protection during thermal treatment, whereas both particle types similarly reduced UVC inactivation. These findings show that PVC microplastics can interfere with microbial control processes and highlight particle morphology as an important factor influencing bacterial survival in aqueous environments.IMPORTANCEMicroplastics are increasingly present in water and food-related environments, but their effects on microbial control processes remain poorly understood. This study demonstrates that PVC microplastics can reduce the effectiveness of both thermal and UVC inactivation of foodborne pathogens in aqueous systems. By developing PVC particles with distinct and defined morphologies, we further demonstrate that particle shape and surface characteristics influence bacterial attachment and survival, particularly during thermal treatment. These findings provide new mechanistic insight into how microplastics may alter bacterial persistence under disinfection or food-processing conditions. This work highlights microplastic morphology as a previously underappreciated factor affecting microbial inactivation and establishes a useful PVC microplastic model system for future studies on microplastic-microbe interactions in environmental and food-associated settings.