A kimchi bacterium doubled the nanoplastics mice passed out

Germ-free mice fed a bacterium isolated from kimchi excreted more than twice as much polystyrene nanoplastic in their feces as untreated mice did. The strain, Leuconostoc mesenteroides CBA3656, comes from the World Institute of Kimchi in South Korea, and the result held in both male and female animals.

The finding is a measure of what leaves the gut, not of what the body keeps. Nanoplastics, particles smaller than a thousandth of a millimeter, can slip across the intestinal wall and have turned up in organs such as the kidneys and brain, which is why a food-grade microbe that helps move them out is attractive on paper. Whether the extra output in the mice translates into less plastic in tissue is a question the authors say they have not answered, and the distinction shapes how far the result can be read. A rise in excreted plastic shows that particles were captured and carried through the gut; it says nothing yet about the particles that had already crossed into the body before the bacterium arrived, or about any harm they might do.

Leuconostoc mesenteroides CBA3656 and the sticking test

The team, led by Drs. Se Hee Lee and Tae Woong Whon at the World Institute of Kimchi, a government-funded institute under South Korea’s Ministry of Science and ICT, began with a screening question: which lactic acid bacteria bind plastic particles best? According to the ScienceDaily account of the work, CBA3656 captured up to 87% of nanoplastics under standard laboratory conditions.

Laboratory buffer is a forgiving place, though, and the gut is not. When the researchers recreated simulated intestinal conditions, CBA3656 still adsorbed 57% of the plastic. A reference strain, Latilactobacillus sakei CBA3608, fell to 3% under the same conditions, NutraIngredients reported, with the 57% figure reached within 60 minutes of exposure. That gap between the two strains is the reason the kimchi isolate went on to animal testing. It also frames the comparison fairly narrowly: the benchmark was one named relative, not the whole family of probiotic bacteria, so the 57% versus 3% contrast describes how CBA3656 fared against that single competitor in simulated gut fluid, not a ranking of all candidates.

Nanoplastics are plastic fragments under one micrometer across, and the particles in this work were polystyrene, a common packaging and foam plastic.

Germ-free mice and the fecal count

For the animal work, the team used germ-free mice, animals raised without any gut microbes of their own, and dosed them with polystyrene nanoplastics. Some received the probiotic and others did not. In both sexes, the treated mice showed what the release describes as “more than a twofold increase in nanoplastics detected in feces” compared with controls. Outlets including Nanowerk and AKIpress repeat the same comparison: treated animals excreted more than double.

The germ-free design is both a strength and the study’s central limit. With no resident microbes, any change in plastic output can be pinned on the added strain rather than on competition or cooperation with an existing gut community. A normal mouse, or a person, carries trillions of bacteria that CBA3656 would have to work alongside, and nothing in the reported results shows whether the strain would stick to plastic as well, or survive as long, in that crowded setting.

Lee has framed the work as a response to a broader worry. “Plastic pollution is increasingly recognized not only as an environmental issue but also as a public health concern,” Lee said, adding that microorganisms from traditional fermented foods could represent a new biological approach to the problem of nanoplastic accumulation.

Limits of a fecal measurement

The study, published in Bioresource Technology (volume 447, article 134234), measured plastic in feces. It did not establish that the bacterium lowered the amount of nanoplastic lodged in tissue, and it did not test any health outcome. The authors say as much: the experiments were controlled laboratory work, and they note that it remains to be determined whether enhanced fecal excretion reduces accumulation or yields measurable benefit in people.

The authors still call the results “a solid experimental basis” for further development, but they caution that “further field-scale and microbiota-integrated studies are necessary” before real-world use can be confirmed. The Microbiologist adds that the mechanism by which intestinal bacteria promote excretion is not yet understood, and that long-term safety data in humans do not exist.

The next experiment the field needs is the one the germ-free design sidesteps: the same strain, the same polystyrene dose, in mice with an intact gut community, with plastic counted in the liver, kidney and brain rather than only in the stool. Bioresource Technology, which carries an impact factor of about 9.0 according to The Microbiologist, has so far published the first half of that story: a strain that binds plastic and a mouse that passes more of it.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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