Understanding the Purpose of Natamycin

October 8, 2025 •

5 min read

Over 150 countries worldwide have approved natamycin for use in various applications. This versatile polyene macrolide antibiotic, also known as pimaricin, serves a dual purpose as a powerful antifungal agent in both the medical and food industries.

Quick Summary

Natamycin functions as an effective antifungal agent by inhibiting yeast and mold growth. In medicine, it is used topically for fungal eye infections, while in the food industry, it serves as a surface preservative to extend shelf life and prevent spoilage.

Key Points

Antifungal Medication: In medicine, the purpose of natamycin is to treat fungal eye infections, such as keratitis, conjunctivitis, and blepharitis, using a topical ophthalmic suspension.
Natural Food Preservative: Natamycin is widely used in the food industry as a surface preservative (E235) to prevent the growth of molds and yeasts on products like cheese and sausage.
Specific Mechanism: It works by binding to ergosterol in the fungal cell membrane, disrupting cellular function and stopping fungal growth, a mechanism that does not affect bacteria.
Low Solubility Advantage: Its low solubility in water is beneficial for food preservation, as it remains on the surface of products where contamination typically occurs.
Minimal Systemic Absorption: When used topically in eye drops or consumed in food, natamycin is minimally absorbed into the body, ensuring localized action and a high safety profile.
Regulated Use: Regulatory bodies like the FDA and EFSA have established safety guidelines and acceptable daily intake limits for natamycin in food applications.

Natamycin: A Potent and Versatile Antifungal Agent

Natamycin, a naturally occurring substance, is a polyene macrolide antibiotic derived from the bacterium Streptomyces natalensis. Its potent antifungal activity, combined with a negligible effect on bacteria, makes it uniquely suited for applications where controlling fungal growth is paramount without disturbing beneficial microbial cultures. The purpose of natamycin is rooted in its ability to bind specifically to ergosterol, a vital component of fungal cell membranes, thereby disrupting membrane function and inhibiting fungal proliferation. This section will explore the two primary uses of natamycin: medical treatment and food preservation.

Medical Applications: Treating Fungal Infections

One of the most well-documented purposes of natamycin is its medical use, primarily in ophthalmology. It is available as a prescription ophthalmic suspension under the brand name Natacyn to treat fungal eye infections. Due to its poor absorption into the bloodstream, it is highly effective for topical administration and poses a minimal risk of systemic side effects.

Specific Ophthalmic Conditions Treated

Fungal Keratitis: An infection of the cornea, which can be caused by various fungi such as Fusarium, Aspergillus, and Candida species.
Fungal Conjunctivitis: An infection of the conjunctiva, the membrane lining the inside of the eyelids and covering the sclera.
Fungal Blepharitis: An infection of the eyelids.

The treatment course for these conditions typically involves applying the eye drops multiple times daily for several weeks, depending on the severity of the infection. It is crucial to complete the full course of treatment, even if symptoms improve, to prevent the infection from returning. Natamycin's poor ability to penetrate an intact cornea makes it particularly effective for infections on the surface of the eye.

Food Preservation Applications: Preventing Mold and Yeast Spoilage

The second major purpose of natamycin is its use as a natural food preservative, designated as E number E235 in the European Union. Its effectiveness against a broad spectrum of yeasts and molds, coupled with its lack of effect on bacteria, makes it an ideal preservative for certain food products. The compound's low solubility in water ensures it remains on the surface of the food product, where mold and yeast contamination typically occurs, rather than migrating into the product and altering its flavor.

Where Natamycin is Used in Food

Cheese: Applied to the surface of cheese rinds via spraying or dipping to prevent mold growth during the aging and storage processes.
Sausages: Used on the casings of dried and fermented sausages to inhibit surface mold.
Baked Goods: Sprayed onto the surface of bread, muffins, and other baked goods to extend shelf life by preventing mold.
Yogurt and Beverages: Used at low concentrations to control yeast and mold growth in yogurt and some beverages.

Advantages in Food Preservation

Using natamycin offers several benefits over other preservatives like sorbates. It diffuses less into the food matrix, preserving the food's natural flavor. It is also effective at low concentrations and is produced naturally, aligning with the growing consumer demand for biopreservation.

Mechanism of Action: The Science Behind the Antifungal Effect

The antifungal mechanism of natamycin is highly specific and differs slightly from other polyene antibiotics. Its primary mode of action is binding to ergosterol, a type of sterol that is a key component of the fungal cell membrane.

How Natamycin Affects Fungal Cells

Irreversible Binding: Natamycin binds irreversibly to ergosterol in the fungal cell membrane.
Membrane Disruption: This binding action does not necessarily create membrane pores like some other polyenes. Instead, it interferes with the function of transport proteins and prevents critical cellular processes like the fusion of vacuoles.
Growth Inhibition: The disruption of essential membrane functions leads to the cessation of yeast and mold growth. Natamycin is considered fungicidal against many organisms at appropriate dosages.

This ergosterol-dependent mechanism explains why natamycin is so effective against fungi while being harmless to bacteria, whose cell membranes do not contain ergosterol.

Comparison of Natamycin's Dual Purpose


Feature	Medical (Ophthalmic) Use	Food Preservation Use
Application Area	Treatment of fungal eye infections, such as keratitis, conjunctivitis, and blepharitis.	Surface treatment of various food products like cheese, sausage, and baked goods.
Mode of Delivery	Topical eye drops (e.g., Natacyn), applied directly to the infected area.	Spraying, dipping, or incorporating into coatings on the food surface.
Absorption	Poorly absorbed into the systemic circulation, ensuring localized action.	Stays on the surface of the food due to low solubility, limiting migration into the product.
Regulatory Status	Approved as a prescription drug (Natacyn) by regulatory bodies like the FDA.	Approved as a food additive (E235) with specific usage limits and conditions in many countries.
Target Microorganisms	Wide range of susceptible fungi, including Candida, Aspergillus, Fusarium, and Penicillium species.	Broad spectrum of molds and yeasts responsible for food spoilage.
Key Benefit	Effectively treats superficial fungal infections of the eye with minimal systemic risk.	Extends shelf life and prevents spoilage without affecting the sensory quality of the food.

Safety and Regulatory Considerations

Natamycin is generally considered safe when used within regulated limits for both medical and food applications. Extensive toxicological studies have established an Acceptable Daily Intake (ADI) for its use in food, and it has been listed as Generally Recognized As Safe (GRAS) by the FDA for specific applications. Regulatory bodies like the European Food Safety Authority (EFSA) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) have evaluated its safety. Concerns about the potential for antimicrobial resistance have been addressed, with findings indicating a low risk for humans through dietary exposure.

Conclusion

The purpose of natamycin is effectively twofold: to serve as a targeted antifungal medication and to act as a valuable natural preservative for a variety of food products. Its unique mechanism of action, which involves binding to ergosterol in fungal cell membranes, allows it to combat yeasts and molds without affecting bacteria or causing significant systemic effects in humans. The stringent regulation of its use in both medical and food contexts ensures its efficacy and safety. As both industries continue to seek effective and safe antimicrobial solutions, natamycin remains a crucial tool, derived from a natural source but with modern-day applications, for preventing spoilage and treating infection.

Natamycin: a natural preservative for food applications—a review

Frequently Asked Questions

Natamycin is a type of polyene macrolide antibiotic, but it is an antifungal medication, not an antibacterial one. It is effective against fungi, yeasts, and molds but has no activity against bacteria or viruses.

Natamycin works by binding to ergosterol, a key component of the fungal cell membrane. This disrupts the membrane's structure and function, inhibiting the fungus's ability to grow and reproduce.

Medically, natamycin's primary purpose is to treat fungal infections of the eye, including keratitis, conjunctivitis, and blepharitis, using an ophthalmic suspension (eye drops).

In food production, natamycin is used as a natural preservative (E235) to prevent the surface growth of molds and yeasts on products like cheese, sausages, and baked goods, which extends their shelf life and ensures safety.

Yes, natamycin is considered safe for consumption within the limits set by regulatory authorities like the FDA and EFSA. Its low solubility and poor absorption mean it remains on the surface of treated foods and poses a low risk.

Unlike some other polyene antifungals that cause membrane leakage by forming channels, natamycin primarily inhibits fungal growth by binding to ergosterol and interfering with critical cellular processes, without necessarily creating pores in the membrane.

Natamycin is applied to the surface because its low solubility prevents it from penetrating deep into the food. This allows it to concentrate its antifungal effect where surface molds are a problem, without affecting the taste or bacterial cultures inside the product.

No, for medical purposes, natamycin ophthalmic suspension is a prescription-only medication, such as the brand name Natacyn.