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

## TL;DR

This study shows that two yogurt bacteria strains can reduce the entry of harmful nanoplastics into intestinal cells, potentially protecting human health.

## Contribution

The study identifies specific yogurt strains that suppress nanoplastic internalization and transcellular permeability in intestinal cells.

## Key findings

- L. bulgaricus 2038 and S. thermophilus 1131 significantly reduced PSNP internalization in Caco-2 cells.
- Both strains suppressed PSNP transcellular permeability, even when non-viable.
- The PSNP suppression effect was strain-dependent, with these strains being the most potent in their species.

## Abstract

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.

The online version contains supplementary material available at 10.1038/s41598-026-39631-z.