关键词: 聚乙烯, 微塑料, 莓实假单胞菌, 生物学特性, 致腐能力

Abstract:

【Objective】This study examined how polyethylene microplastics (PE-MPs) affected the physiological traits, surface colonization, and spoilage potential of Pseudomonas fragi (P. fragi) and explored the processes involved at microbe-food interfaces. 【Method】The strongly spoilage-associated strain P. fragi NMC25 was selected as the model organism. Based on field data from meat-processing environments, two environmental relevant concentrations were tested: a meat-migration concentration (35 μg·mL^-1) and a cutting-board residual concentration (700 μg·mL^-1). Effects across key stages of microbial spoilage were systematically assessed using growth curve analysis, motility assays, biofilm quantification, microscopy, and spoilage-indicator measurements. 【Result】PE-MPs did not significantly affect the growth capacity of P. fragi, even at the cutting-board residual concentration. This finding indicated that PE-MPs did not directly impair bacterial proliferation. At the cutting-board residual concentration, PE-MPs significantly enhanced swimming, swarming, and twitching motility (P<0.05). They also promoted bacterial adhesion to and colonization of stainless-steel surfaces. At the meat-migration concentration, only twitching motility increased significantly (P<0.05). These findings indicated that PE-MPs could stimulate local surface translocation, with a greater effect at the higher concentration. Scanning electron and confocal laser scanning microscopy revealed that bacterial cells accumulated around microplastic particles and secreted abundant extracellular polymeric substances that enveloped the cells. Together, these cell-particle assemblages formed complex three-dimensional reticular biofilm structures. At the cutting-board residual concentration, the biofilms exhibited increased extracellular polymeric substance production, with more compact architecture and clustered spatial distribution. Regarding spoilage potential, PE-MPs at the residual concentration significantly increased extracellular protease activity. This increase was accompanied by significantly greater rises in total volatile basic nitrogen (TVBN) and pH than that in the control. These changes accelerated sensory deterioration in chilled meat samples. 【Conclusion】At the cutting-board residual concentration, PE-MPs promoted dense biofilm formation and accelerated proteinaceous-substrate spoilage without altering bacterial growth. These effects were associated with enhanced motility, surface adhesion, and protease activity. High PE-MP loaded on cutting boards might therefore facilitate spoilage-bacterial colonization and food spoilage in food-processing environments. These findings provide a basis for incorporating microplastic-mediated microbial effects into food-safety risk assessments.

Key words: polyethylene, microplastics, Pseudomonas fragi, biological characteristics, spoilage potential