Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131 suppress polystyrene nanoplastic transcellular permeability and internalization by intestinal epithelial cells.

The plastic is broken into nanoscale particles (nanoplastics) that are harmful to the human body. Nanoplastics orally ingested are internalized into various cells, causing adverse effects such as oxidative stress and apoptosis; however, methods for preventing nanoplastic internalization are lacking. By elucidating this method, it is possible to make a significant contribution to human health. Then, following previous reports that Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131 ameliorated barrier dysfunction in the small intestine, we examined their effects on the internalization of polystyrene nanoplastics (PSNPs) in a differentiated Caco-2 monolayer by flow cytometry and immunofluorescent staining. Both yogurt starter strains significantly suppressed fluorescently labeled PSNP internalization by Caco-2 cells, even when the strains were non-viable. Moreover, both strains significantly suppressed the transcellular permeability of PSNPs, suggesting reduced PSNP accumulation in blood vessels and various tissues. Finally, the suppression of PSNP internalization was strain dependent, and both strains were the most potent strains among multiple strains from the same species. This study highlights the potential of L. bulgaricus 2038 and S. thermophilus 1131 for ameliorating the adverse health effects of PSNP intake.