PET microplastics affect human gut microbiota communities during simulated gastrointestinal digestion, first evidence of plausible polymer biodegradation during human digestion

INTRODUCTION

The prevalence of plastic particles in the food chain has raised the concern about health effects of microplastics ingestion. In fact, the presence of polyethylene terephthalate (PET) particles in human faeces suggests their active interaction with the human digestive system. Chronic exposition could lead to microplastic-induced gut dysbiosis in several species, which might be linked to host health. However, microplastic changes during human gastrointestinal digestion or colonic fermentation are scarcely explored.

MATERIALS AND METHODS

To evaluate the potential risks of microplastics at the digestive level, we simulated the complete transit of a single dose of PET through the gastrointestinal tract. Gastrointestinal digestion and colonic fermentation were simulated combining harmonized static model INFOGEST (oral, gastric and intestinal steps) with the dynamic gastrointestinal model simgi® for the large intestine step, including human colonic microbiota in physiological conditions. Figure 1. Experimental setup of the present study Analysis of microplastic morphology and chemical structure were carried out at the original PET particles and at the different gastrointestinal simulated steps. Changes in microbiota composition were studied by plate counting methods and microbial 16S rRNA gene-based sequencing analysis.

RESULTS

FESEM images revealed an evolution of the surface after gastrointestinal digestion, indicative of a slight interaction with the media, which resulted, according to Raman characterization, with a relative amorphization of the PET structure, but no remarkable morphological changes. Some organic deposits were also found, they were remarkable after colonic fermentation. Indeed, most PET microplastics seemed to be colonized by some members of the colonic microbiota, and the surface roughness evolved to a globular surface. PET microplastic intake affects composition and diversity of the microbial communities, specially at distal colon.

CONCLUSIONS

PET microplastics are capable of digestive-level transformations and health effects:

• PET microplastics started several biotransformations in the gastrointestinal tract

• At colonic level the microplastics appeared to be structurally different from the original particles

• The feeding with PET microplastics altered human microbial colonic community composition in simgi® model

• Some members of the colonic microbiota could adhere to microplastics surface promoting the formation of biofilms

Considering the increasing exposure to microplastics, their impact on the functionality of the gut microbiome and their potential biodegradation in the human gastrointestinal tract merits critical investigation.