Designer Microbes Turn Fermented Foods Into Molecular Scrubbers for Fungal Toxins

Mycotoxins, the toxic secondary metabolites produced by filamentous fungi such as Aspergillus, Penicillium and Fusarium, are among the most stubborn contaminants in the global food supply. They resist heat, survive conventional processing, and slip past good agricultural practices with alarming ease. A sweeping systematic review published in Current Research in Biotechnology now maps how beneficial microorganisms, from probiotic lactic acid bacteria to engineered starter cultures, could be deployed as biological molecular scrubbers across the entire journey of a toxin, from the fermenting food matrix to the human gut wall.

The research team, led by Imane E.L. Houssni, screened 1,055 records retrieved from Scopus, Web of Science, PubMed and ScienceDirect and retained 388 high-rigor studies after a PRISMA-guided triage that eliminated uncharacterized adsorbents, superficially descriptive biocontrol assays and reports lacking mass-balance verification. Inter-reviewer agreement was high, with a Cohen’s kappa of 0.88. The resulting synthesis organizes the field around a four-pillar framework: upstream inhibition of toxigenic fungi, passive physical sequestration, active enzymatic biotransformation, and downstream protection of the host’s intestinal barrier.

The first mechanistic pillar, biosorption, is deceptively simple. Toxin molecules bind to the microbial cell wall, a scaffold of peptidoglycan, teichoic acids, beta-glucans and surface-layer proteins, through electrostatic attraction, hydrophobic intercalation and steric entrapment. Crucially, this process does not require living cells. Heat-killed paraprobiotics work just as well, sidestepping risks of horizontal gene transfer in processed foods. Spectroscopic and microscopy studies show that peptidoglycan cross-linking and the charge density of teichoic acids dictate binding stoichiometry, while yeast beta-glucan triple helices form high-affinity pockets that capture zearalenone through hydrophobic insertion of its macrocyclic lactone ring.

Yet the review is blunt about biosorption’s Achilles heel: reversibility. Binding equilibria that look impressive in a static flask can collapse in the gut, where pH swings from gastric acidity to intestinal neutrality, bile salts micellize lipophilic toxins, digestive enzymes chew up cell-wall proteins, and peristaltic shear pries complexes apart. The authors argue that static isotherm parameters such as maximum adsorption capacity cannot be extrapolated to prove in vivo sequestration; definitive validation demands dynamic multi-compartmental simulators like TIM-1 and SHIME, plus fecal recovery assays.

The second pillar, enzymatic biotransformation, offers a permanent solution by chemically remodeling toxic pharmacophores. Lactonohydrolases of the ZHD102 family cleave zearalenone’s macrocyclic ester into hydrolyzed ZEN, a product devoid of estrogenic activity. Anaerobic gut commensals such as Eubacterium BBSH 797 express epoxide reductases that convert deoxynivalenol into the non-toxic DOM-1, disarming the molecule’s ability to inhibit ribosomal protein synthesis. For ochratoxin A, metalloproteases cleave the amide bond linking the phenylalanine moiety to the isocoumarin nucleus, yielding ochratoxin alpha, which is negligibly toxic and rapidly cleared by the kidneys. Fumonisin B1 detoxification proceeds in two steps: a carboxylesterase such as FumD strips the tricarballylic acid side chains, then an aminotransferase deaminates the C-2 amine, abolishing the toxin’s interference with ceramide synthase.

But the review insists on a critical caveat: biotransformation is not automatically detoxification. Some conversions backfire spectacularly. Zearalenone can be reduced to alpha-zearalenol, which binds estrogen receptors more avidly than the parent toxin. Genuine detoxification therefore requires full structural identification of every degradation product by high-resolution mass spectrometry or NMR, complete mass-balance closure, and bioassay-driven toxicological validation to rule out masked or paradoxically toxic intermediates.

The third and most surprising pillar reframes probiotics as biological shields rather than mere toxin sponges. Administered strains fortify the intestinal epithelium by upregulating tight junction proteins, including zonula occludens-1, occludin and the claudins, while suppressing the pathological hyperactivation of p38 MAPK and NF-kappa-B that deoxynivalenol and ochratoxin A trigger through ribotoxic stress. They also stimulate goblet cells to thicken the MUC2 mucus layer, promote secretory IgA secretion from gut-associated lymphoid tissue, and activate the host’s Nrf2 antioxidant pathway to restore the glutathione redox ratio. Perhaps most strikingly, postbiotic metabolites such as butyrate act as histone deacetylase inhibitors, a postbiotic-epigenetic bridge that remodels chromatin and transcriptionally reprograms barrier-restoring genes.

In the food industry, these mechanisms are converging on the concept of smart starters, bifunctional cultures that ferment the product while scrubbing it clean. Multi-strain lactobacilli consortia have achieved aflatoxin M1 reductions exceeding 60 percent in yogurt models, Lactiplantibacillus plantarum strains bind 65 to 85 percent of aflatoxin B1 in sourdough matrices, and the yeast Kluyveromyces marxianus removes 85 to 95 percent of zearalenone while enriching products with aromatic esters and B vitamins. The challenge is preserving taste and texture: over-acidification, off-flavors and proteolytic degradation can sink consumer acceptance regardless of molecular efficacy, and matrix components like milk fat can physically shield toxins from microbial contact.

The review also confronts the field’s methodological blind spots. Two strains of the same species can differ in binding capacity from under 10 percent to over 80 percent, real-world contamination involves multi-toxin cocktails that saturate binding sites, and masked mycotoxins such as deoxynivalenol-3-glucoside evade screening until gut hydrolases release the parent toxin in situ. Human trials remain scarce and often rely on indirect urinary biomarkers, while responder-versus-non-responder microbiome heterogeneity complicates regulatory validation by EFSA and the FDA.

Looking forward, the authors sketch a roadmap toward designer microbes: CRISPR-engineered chassis with densified adsorptive cell walls and heterologous detoxification enzymes, programmable biosensors that secrete enzymes only when luminal toxin spikes are detected, artificial intelligence-driven molecular docking to predict binding energies, gut-on-a-chip platforms and human intestinal organoids for physiologically faithful validation, and pH-responsive nano-encapsulation that delivers payloads exactly where absorption risk peaks. The smart starter concept currently sits at low technology readiness levels, but the trajectory is clear. Fermented foods, once viewed as a passive vector of dietary risk, are being reimagined as precision instruments of xenobiotic resilience, turning the trillions of microbes in our food and gut into an active, engineered line of defense against one of the oldest poisons in the human diet.

Subject of Research: Microbial mechanisms of mycotoxin detoxification in fermented foods and the gastrointestinal tract

Article Title: Microbial mycotoxin mitigation across the microbe–matrix–host continuum: mechanisms, fermented-food applications, and gastrointestinal translation

Article References: HOUSSNI, I. E., ZAHIDI, A., FAKIR, S. E., JAIMA, W., & HASSIKOU, R. (2026). Microbial mycotoxin mitigation across the microbe–matrix–host continuum: mechanisms, fermented-food applications, and gastrointestinal translation. Current Research in Biotechnology, Article 100421. https://doi.org/10.1016/j.crbiot.2026.100421

Image Credits: AI Generated

DOI: 10.1016/j.crbiot.2026.100421

Keywords: mycotoxins, probiotics, biosorption, biotransformation, lactic acid bacteria, fermented foods, gut barrier, aflatoxin, zearalenone, ochratoxin A, smart starters, food safety