The slimy coating on nameko mushrooms, a staple in Japanese miso soup, turns out to be remarkably good at grabbing tiny plastic particles suspended in water. Researchers at Shinshu University in Nagano, Japan, reported in April 2026 that mixing the mushroom’s natural slime with iron ions created sticky, web-like structures capable of trapping polystyrene fragments as small as 100 nanometers. Their best result: a 98.4% removal rate, achieved using nothing more than the leftover water from rinsing the mushrooms before cooking.
The findings, published in the journal Chemosphere, land at a moment when microplastic contamination in drinking water has become a global concern. Conventional treatment plants often struggle with the smallest fragments, and a cheap, biodegradable filter material pulled from an edible fungus could eventually offer treatment operators a new tool, though significant hurdles remain before that happens.
How the mushroom method works
Nameko mushrooms (Pholiota nameko) produce a thick, gel-like mucilage on their caps. Earlier Japanese food chemistry research established that this slime is rich in pectin, a polysaccharide familiar to anyone who has made jam. The Shinshu University team extracted the mucilage by simply shaking the mushrooms in water, then added iron(III) ions to the solution. The iron caused the pectin chains to cross-link into a three-dimensional fibrous network, forming clumps called flocs. Suspended plastic particles stuck to those flocs through electrostatic attraction and were pulled out of the water as the clumps settled.
The process closely mirrors coagulation and flocculation, steps already used in most municipal water treatment plants. Operators routinely add metal salts like aluminum sulfate or ferric chloride to make suspended solids clump together and settle. The nameko approach essentially replaces synthetic polymers in that process with a mushroom-derived biopolymer, potentially improving capture of very fine particles that slip through standard treatment.
The numbers behind the headline
The team tested their method against polystyrene particles at two sizes. For 1.0-micrometer microplastics, the purified mucilage extract removed 95.3%. For 100-nanometer nanoplastics, the rate was 87.4%. The highest figure, 98.4%, came from a separate test using nameko-washing wastewater, the rinse water left over after preparing the mushrooms. A Shinshu University news summary confirmed these percentages.
Those results look competitive when measured against conventional treatment. A 2020 study by Ma et al. in Water Research, indexed in PubMed, examined how standard drinking water plants handle micro- and nanoplastics ranging from 180 nanometers to 125 micrometers. It found that removal does occur during normal coagulation and filtration, but efficiency drops sharply for the smallest particles. The nameko method’s strong performance at the 100-nanometer scale is what makes it stand out.
The 98.4% figure deserves a closer look, though. Because it came from washing wastewater rather than purified mucilage, the rinse water likely contained additional organic compounds, including proteins and other polysaccharides, that may have boosted floc formation. The study does not fully isolate which components drove the higher rate. That number is best understood as a peak laboratory result, not a guaranteed performance standard.
What the study did not test
Every removal rate in the paper was measured using uniform polystyrene spheres in carefully controlled conditions, with adjusted pH and ionic strength. Real drinking water is far messier. It contains a mix of plastic types, natural organic matter, sediment, and dissolved chemicals, all of which can interfere with coagulation. Natural organic matter, for instance, can compete with plastics for binding sites on the flocs or alter how the pectin network forms. No pilot-scale trial at an actual treatment plant has been conducted, and no cost comparison against conventional coagulants has been published.
The fate of the resulting sludge is another open question. Iron-pectin-plastic flocs have to go somewhere after they are separated from the water. Whether that sludge can be safely landfilled, incinerated, or processed for plastic recovery has not been addressed. Each disposal route carries different environmental trade-offs that the current research leaves unexplored.
Supply logistics also pose challenges. Nameko mushrooms are cultivated commercially in Japan, China, and parts of Europe, but diverting large volumes of mushrooms or their wash water to treatment plants would require new collection infrastructure. Concentrating the mucilage into an industrial product is another option, but it would add manufacturing steps and costs that have not been evaluated. The study does not address how stable the mucilage is during storage or how batch-to-batch variation in mushroom composition might affect performance.
A growing field of competitors
The nameko method is not the only biodegradable approach under investigation. Researchers have tested chitosan-based coagulants, derived from crustacean shells, paired with microbubble technology to remove microplastic fibers. Other teams have explored electrophoretic deposition combined with foam separation to pull nanoplastics from industrial wastewater, though published details on those techniques vary in specificity. No head-to-head comparison of these methods under identical conditions has been published, making it impossible to rank them. The nameko technique is one promising entry in a crowded and fast-moving field.
Where the science goes next
The Shinshu University results clear an important early bar. The team demonstrated high removal rates for model particles, offered a clear mechanistic explanation rooted in well-understood pectin chemistry, and showed that even unprocessed mushroom rinse water carries enough active biopolymer to be useful. That combination of effectiveness, low cost, and biodegradability is what makes the work genuinely interesting rather than just novel.
But laboratory proof of concept is only the first step. Before mushroom slime shows up at a water treatment plant near you, researchers will need to test it against the full spectrum of plastic types found in real source water, run pilot trials at working facilities, evaluate sludge disposal options, and compare costs with the coagulants already in use. Those studies could take years. For now, the finding is best understood as a compelling early result: evidence that a common kitchen mushroom produces a substance with real potential to help solve one of the more stubborn pollution problems in modern water treatment.
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*This article was researched with the help of AI, with human editors creating the final content.
