The Primary Microbial Source of Natamycin
Natamycin, a polyene macrolide antimycotic, is a secondary microbial metabolite produced by certain strains of the Streptomyces bacteria. The most well-known and primary species responsible for its production is Streptomyces natalensis. This bacterium was first isolated from a soil sample collected in Pietermaritzburg, South Africa, in 1955, leading to the initial naming of the compound as pimaricin. The name was later changed to Natamycin, derived from the natalensis species. The discovery highlighted the potential of soil-dwelling microorganisms as sources for potent and useful biochemical compounds.
Commercial Fermentation and Production Process
Commercial production of natamycin relies on a controlled biotechnological process known as submerged fermentation. This method is the most efficient and scalable for producing high yields of the compound for both food and pharmaceutical applications. The process involves several key steps that optimize the conditions for the Streptomyces bacteria to produce natamycin.
Key Steps in Natamycin Production:
- Inoculum Preparation: A starter culture, or inoculum, of a natamycin-producing Streptomyces species (like S. natalensis or S. gilvosporeus) is grown in a nutrient-rich medium.
- Submerged Aerobic Fermentation: The inoculum is transferred to a larger fermentation tank containing a liquid medium. The process is kept aerobic, meaning it requires oxygen, and is mechanically agitated to ensure homogeneity.
- Nutrient Control: The fermentation medium contains a carbon source (e.g., glucose, starch, or molasses) and a fermentable nitrogen source (e.g., corn steep liquor, soy protein, or casein). Conditions like temperature (around 26–30°C) and pH (controlled between 6 and 8) are carefully monitored and maintained for maximum yield.
- Extraction and Purification: Due to its low solubility, natamycin accumulates as crystals within the fermentation broth. After fermentation, the biomass is separated, and the natamycin is extracted using organic solvents and further purified through filtration processes.
- Drying and Formulation: The purified natamycin is then spray-dried into a crystalline powder for commercial use, often mixed with an incipient like lactose, glucose, or salt.
Comparison: Natamycin vs. Synthetic Alternatives
Natamycin is often compared to synthetic food preservatives like sorbates. While both extend the shelf life of food by inhibiting microbial growth, their sources and characteristics differ significantly, influencing their application and regulatory status.
| Feature | Natamycin (Natural, Microbially-Derived) | Common Synthetic Preservatives (e.g., Sorbates) |
|---|---|---|
| Source | Produced naturally by Streptomyces bacteria via fermentation. | Artificially synthesized chemicals. |
| Antimicrobial Spectrum | Highly specific and effective against a broad range of yeasts and molds. | Also effective against molds and yeasts, but with a broader antimicrobial range. |
| Effect on Bacteria | No effect on bacteria, making it ideal for fermented products like cheese and sausage without harming beneficial bacterial cultures. | Can inhibit the growth of some types of bacteria. |
| Food Application | Poor water solubility means it remains primarily on the surface, making it suitable for surface treatments. | High water solubility allows it to be incorporated throughout the food product. |
| Regulatory Status | Approved worldwide as a safe food additive (E235) and for ophthalmic medical use. | Approved worldwide, but consumer demand often favors "natural" alternatives. |
| Consumer Perception | Viewed favorably as a "natural" antimicrobial, aligning with consumer demand for clean-label ingredients. | Can be perceived negatively as a chemical additive. |
Diverse Applications in Food and Medicine
The dual nature of natamycin as both a potent antifungal agent and a natural preservative is its major strength. In the medical field, it is used as an ophthalmic suspension (eyedrops) to treat fungal eye infections like keratitis, blepharitis, and conjunctivitis caused by sensitive fungal species. Its low absorption into the body makes it suitable for topical use.
As a food preservative, natamycin is particularly valuable due to its high efficacy at low concentrations and its specific action against molds and yeasts. Its poor water solubility allows it to remain on the surface of foods, providing protection without significantly diffusing into the product. It is widely used for surface treatment of cheese and sausages and can be added to yogurts, cottage cheese, sour cream, and certain beverages. Its use helps to extend the shelf life of these products and prevent the formation of potentially harmful mycotoxins.
Conclusion
In conclusion, the source of Natamycin is the fermentation of specific strains of the Streptomyces bacterium, primarily Streptomyces natalensis. This natural microbial origin, combined with its selective and potent antifungal properties, makes it a valuable compound in both the pharmaceutical industry and food preservation. Produced commercially through a well-controlled submerged fermentation process, natamycin offers a safe and effective alternative to synthetic preservatives for inhibiting mold and yeast growth in a variety of foods. Its dual application and natural origin secure its place as a crucial compound in both health and food science.
Outbound Link
For further information on Natamycin's use in ophthalmology, see the Mayo Clinic's drug information page on Natamycin.
