When Bacteria Disarm Fungi: How Biosurfactants May Reduce Mycotoxins in Crops

The Problem That Outlasts the Mold

Fungal contamination in agriculture is usually treated as a visibility problem. You see the damaged grain, the spoiled batch, the discolored kernels — and you intervene. But this framing misses the more durable part of the challenge.

Many crop-associated fungi produce mycotoxins: chemical compounds that persist in grain, feed, and processed food products long after visible fungal growth has subsided. A field that looks clean after treatment may still carry a chemical legacy that poses real risks to human and animal health. Stopping the fungus is necessary. It is not sufficient.

This reframes what effective crop protection actually requires. The target is not only fungal biomass — it is fungal biochemistry.

A Strategy Built on Microbial Competition

Soil and plant surfaces are not sterile environments. They are contested spaces where bacteria, fungi, and other microorganisms continuously interact, compete, and chemically signal one another. Researchers exploring biological crop protection are increasingly interested in harnessing those dynamics rather than overriding them with synthetic chemicals.

One such approach involves biosurfactants, naturally produced compounds generated by bacteria that interact with microbial membranes and cellular systems in ways that disrupt fungal growth and metabolism. Unlike broad-spectrum fungicides that suppress microbial activity indiscriminately, biosurfactants function through targeted biological interactions — working with the logic of microbial competition rather than against it.

The study examined two biosurfactants: amphisin, produced by Pseudomonas fluorescens, and rhamnolipids, produced by Pseudomonas aeruginosa. Both were generated using food-industry waste streams as production substrates — a detail that connects the crop protection application to a broader circular-resource framework.

The Key Finding: Toxin Production, Not Just Fungal Growth

The headline result of this research is not that biosurfactants inhibit fungal growth — though they do. It is that they directly suppress mycotoxin production.

In controlled experiments, both compounds significantly reduced the production of sterigmatocystin, a mycotoxin structurally and toxicologically related to aflatoxin. The reduction ranged from 89% to 99%, with rhamnolipids demonstrating the stronger effect.

This distinction carries real weight for food safety applications. The presence of fungi in a grain sample does not automatically determine contamination risk — toxin production is what transforms fungal presence into a food safety problem. A treatment that reduces visible mold but leaves toxin biosynthesis intact addresses the symptom without resolving the underlying hazard. Biosurfactants, in this study, demonstrated the capacity to intervene at the biochemical level where the actual risk originates.

How Biosurfactants Work — and Where They Have Limits

Biosurfactants interact with fungal systems through multiple mechanisms. They disrupt cell membrane integrity, interfere with metabolic processes, and can inhibit the signaling pathways involved in secondary metabolite production — including the biosynthesis of mycotoxins.

This multi-mechanism mode of action is one of the features that distinguishes biosurfactants from conventional fungicides, which typically target a single pathway. The complexity of the interaction may reduce the likelihood that fungi can develop resistance through a single adaptive mutation, a growing concern with existing chemical treatments.

However, the study also identifies a meaningful limitation: biosurfactant activity declined over time, with effectiveness highest during early stages of fungal growth. Whether this reflects environmental degradation of the compounds, fungal adaptation, or instability in the experimental conditions remains to be clarified. What is clear is that biosurfactants are not a set-and-forget solution. They are most relevant as early-stage or preventive interventions, and their role in a practical crop protection system is likely complementary rather than primary.

Waste as a Production Resource

The production method used in this study deserves attention beyond its technical detail. Both biosurfactants were generated using food-industry waste streams as bacterial growth substrates — residual materials that would otherwise require disposal.

This positions biosurfactant production within a circular-economy logic: waste from one process becomes the input for another, and the output is a functional agricultural product. The environmental footprint of the crop protection agent is reduced not only by its biodegradability in the field but by the sustainability of its production process upstream.

This integration of waste valorization and bioactive compound production is increasingly relevant as agricultural systems face pressure to reduce chemical inputs and environmental impact simultaneously. Biosurfactants produced from food waste represent one concrete example of how those pressures can be addressed within a single system.

Where This Fits in the Future of Crop Protection

The trajectory of crop protection is moving away from dependence on single-mechanism chemical solutions and toward integrated systems that combine biological agents, environmental monitoring, and targeted interventions deployed at the right stage of the production cycle.

Biosurfactants, as this research positions them, are candidates for the post-harvest and storage portion of that system — the stage where fungal contamination and toxin accumulation remain persistent challenges and where the limitations of field-applied fungicides are most apparent. Grain storage environments are controlled enough to allow more precise application, and the consequences of mycotoxin accumulation in stored grain are direct and economically significant.

Scaling this from laboratory results to practical agricultural application requires resolving questions of formulation stability, application logistics, cost competitiveness, and performance across diverse grain types and storage conditions. The study does not answer those questions. What it provides is a clear demonstration that the underlying biological mechanism — direct suppression of mycotoxin biosynthesis — is real and reproducible.

Rethinking the Microbial Landscape

There is a broader principle embedded in this line of research. Bacteria and fungi do not exist in isolation. They share environments, compete for resources, and chemically influence one another in ways that have been shaped by millions of years of co-evolution.

The conventional agricultural response to fungal contamination has been to introduce synthetic chemicals into this system — disrupting the microbial ecology of a field or storage facility in ways that are effective in the short term but carry cumulative costs. Biological approaches like biosurfactant application work differently. They operate through the existing logic of microbial competition, deploying compounds that bacteria already produce naturally, to shift the balance of a microbial ecosystem in a direction that benefits crop safety.

This is not a wholesale alternative to chemical fungicides, at least not yet. But it represents a meaningful expansion of the toolkit — one grounded in ecology rather than chemistry, and aligned with the direction that sustainable agriculture is moving.

FAQ

Can biosurfactants replace chemical fungicides in agriculture? Not currently. They are most effectively positioned as complementary tools within integrated crop protection systems, particularly for post-harvest and storage applications.

Do biosurfactants only reduce fungal growth? No. This study demonstrated that they can also directly suppress mycotoxin production — a food safety benefit that goes beyond simply limiting visible fungal contamination.

Are biosurfactants environmentally safe? Generally, yes. They are biodegradable and can be produced from food-industry waste streams, giving them a lower environmental footprint than many synthetic alternatives.

Why does reducing mycotoxins specifically matter? Mycotoxins persist in grain and processed food products even after fungal growth is no longer visible. Controlling toxin production is essential for long-term food safety, not just cosmetic crop quality.

Are biosurfactants already used commercially in agriculture? Not at scale. Further development is needed to confirm stability, efficacy across real-world conditions, and cost-effectiveness before commercial deployment becomes feasible.

References

1. Scientific Reports (2025). Biosurfactant-mediated reduction of mycotoxin production in crop-associated fungi. Scientific Reports. https://www.nature.com/articles/s41598-025-31914-1