Kimchi bacterium helps mice flush nanoplastics from their bodies

A bacterium isolated from kimchi caused mice to excrete more than twice as many nanoplastic particles in their feces as untreated animals, according to researchers at South Korea’s World Institute of Kimchi. The strain, Leuconostoc mesenteroides CBA3656, appears to grab onto microscopic plastic fragments as they pass through the gut and carry them out of the body rather than letting them linger and potentially cross into tissue. The finding, published in the journal Bioresource Technology, is among the first to show a specific gut microbe actively binding nanoplastics in a living animal rather than in a test tube alone.

An 87% grip in the lab, a weaker one in the gut

Se Hee Lee and Tae Woong Whon, researchers at WiKim who led the work, first tested the strain’s raw binding capacity under standard laboratory conditions, where it adsorbed 87% of the polystyrene nanoplastics it was exposed to. A comparison strain, Latilactobacillus sakei CBA3608, performed almost as well in that setting, adsorbing 85%. The real test came when the researchers simulated the harsher, more acidic environment of the human intestine: CBA3656’s performance dropped but held at 57%, while the comparison strain’s adsorption collapsed to just 3%, a gap wide enough to suggest CBA3656 has some structural feature that keeps it functional where ordinary lactic acid bacteria fail.

“Plastic pollution is increasingly recognized not only as an environmental issue but also as a public health concern,” Lee said, framing the lab result as a starting point rather than the study’s main claim. The gut-condition figure, not the higher lab number, is what the team considers the more realistic estimate of what the bacterium could do inside a living digestive system.

From a petri dish to a mouse’s feces

To test that estimate, the WiKim team moved to germ-free mice, animals raised without their own gut microbiome so that any effect could be attributed to the introduced bacterium rather than competing microbes already present. Male and female mice given strain CBA3656 alongside a nanoplastic dose showed more than a twofold increase in nanoplastics recovered from their feces compared with control mice that received the plastic without the bacterium. That result, described in the EurekAlert release accompanying the paper, is the first the WiKim group has published showing the binding effect translating into actual increased excretion in a live animal, rather than just plastic sticking to bacteria on a lab bench.

The mechanism the researchers propose is straightforward: the bacterium’s cell wall binds to nanoplastic particles in the gut, and because the bacterium itself continues through the digestive tract and out of the body, whatever plastic has attached to it goes along for the ride. It is a passive, physical process rather than one requiring the bacterium to break the plastic down chemically, which the team says makes it easier to reproduce reliably across different plastic types and concentrations.

WiKim has been building toward this result for months. An earlier release from the institute described the same lab’s initial adsorption screening across multiple candidate bacterial strains before CBA3656 and the mouse work narrowed the field to the one strain that performed best under gut-like conditions. That earlier stage is what let the team focus its live-animal testing on a single, already-promising candidate rather than screening dozens of strains in mice, which would have taken considerably longer and required far more animals.

Limits of a mouse study

WiKim’s president, Hae Choon Chang, has framed the work as part of a longer institutional effort connecting fermented food research to broader health applications, an effort covered separately by Phys.org when the underlying strain data first circulated. But mice are not people, and germ-free mice in particular have simplified gut environments that do not reflect the crowded, competitive microbiome of a normal human digestive tract, where thousands of other bacterial species could interfere with CBA3656’s ability to bind plastic before excretion.

The WiKim team has not published human trial data, and it remains unknown whether eating kimchi itself delivers a meaningful dose of live CBA3656 capable of reproducing the mouse results, since fermentation, storage and stomach acid could all reduce how much of the bacterium survives to reach the intestine intact. Earlier work from the same institute, summarized by The Microbiologist, focused only on the laboratory adsorption data now confirmed and extended by the mouse experiments.

Whether an isolated, concentrated probiotic supplement rather than the fermented vegetable dish itself would be needed to reach a therapeutic dose is a question the WiKim team has flagged for its next phase of research, alongside testing whether the effect holds for plastic types beyond the polystyrene used in this study. Concern over nanoplastic exposure generally, from packaging, textiles and tire wear, has grown enough in recent years that a gut-level intervention, even one still confined to mice, has drawn attention well beyond the fermented-food research community WiKim normally serves.

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

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