As the aquaculture industry seeks eco-friendly alternatives, pigmented fungi and yeasts have emerged as promising solutions. These microorganisms not only enhance fish pigmentation but also improve growth, immune function, and overall health.
A study published by researchers from the Agricultural University of Athens in Aquaculture International explores the potential of pigmented fungi in aquaculture, their benefits, and the science behind their application.
What are the benefits of pigmented fungi for the aquaculture industry?
The main benefits of using pigmented fungi in aquaculture, according to sources, include:
Sustainable alternative to marine ingredients
Pigmented fungi offer an option to replace marine-derived ingredients in fish feed, reducing dependence on costly and limited resources.
Pigmentation enhancement
Pigmented fungi improve the color of fish flesh and skin, an important quality factor influencing consumer decisions and the market value of aquaculture species. For example, suboptimal fillet pigmentation can reduce the economic value of rainbow trout fillets by up to 40%.
Growth promotion and overall health
Pigmented fungi contribute to better growth, general health, and immunity in fish. The natural pigments found in these fungi, such as carotenoids, have antioxidant and antimicrobial properties that benefit aquatic organisms by stimulating the immune system, increasing stress resistance, and promoting growth and maturation.
Replacement of synthetic pigments
Pigmented fungi serve as a natural and safe alternative to synthetic pigments, which have significant drawbacks such as environmental and health risks, side effects, and potential carcinogenicity. Microbial pigments offer advantages related to fermentation, which is faster and ensures more efficient production than any chemical process.
Effects on lipid metabolism
Carotenoids present in pigmented fungi reduce total lipids in fish while increasing essential fatty acids such as EPA and DHA. Astaxanthin supplementation decreases lipid percentages and improves lipid utilization in Pagrus pagrus.
Antioxidant activity
Fungal pigments combat oxidative stress, protecting fish from cellular damage. Carotenoids, for instance, can scavenge singlet molecular oxygen, ROS, and other free radicals.
Immune system enhancement
Pigmented fungi strengthen fish immune systems, making them more resistant to diseases. R. glutinis pigments have antibacterial effects, mainly against Gram-positive bacteria, and to a lesser extent against Gram-negative bacteria.
Reproductive improvement
Carotenoids found in pigmented fungi improve egg quality and increase fish fecundity. The inclusion of astaxanthin in salmon and sea bream diets has been shown to enhance ovarian development, fertilization, hatching, and larval growth.
The problem with synthetic pigments
Although synthetic pigments such as astaxanthin have dominated the market, they present significant limitations:
- Environmental and Health Risks: Associated with public health concerns and environmental pollution.
- Side Effects: Some studies suggest they may have pro-oxidant effects and even carcinogenic properties.
How pigmented fungi improve fish health and growth
Scientific literature reports that pigmented fungi, such as Phaffia rhodozyma and Monascus purpureus, enhance fish growth, lipid metabolism, and immune responses.
For example, studies have shown that Phaffia rhodozyma, rich in astaxanthin, improves the growth parameters of rainbow trout and enhances lipid utilization. Similarly, Monascus purpureus has been found to reduce feed conversion ratios in shrimp, indicating better feed efficiency.
These fungi also play a role in lipid metabolism. Carotenoids such as astaxanthin have been shown to reduce total lipids in fish muscle and liver while increasing essential fatty acids like EPA and DHA. This not only improves fish health but also enhances the nutritional value of fish for consumers.
Natural pigmentation: A commercial advantage
Fish pigmentation is a critical factor influencing consumer preferences and market value. Naturally derived pigments from fungi, such as astaxanthin and β-carotene, are increasingly preferred over synthetic alternatives due to their safety and environmental benefits.
Fungal-derived pigments are eco-friendly and offer additional health benefits, such as antioxidant and antimicrobial properties.
For instance, Phaffia rhodozyma has been used to enhance red pigmentation in salmon and trout, meeting market demands for vibrant coloration. Similarly, Rhodotorula species have been shown to improve the coloration of ornamental fish such as koi carp, making them more attractive to consumers.
Immune system enhancement and disease resistance
Pigmented fungi also contribute to improved immune function in fish. Carotenoids such as astaxanthin and β-carotene enhance immune responses, reducing disease risk in aquaculture. For example, Rhodotorula mucilaginosa has been found to increase lysozyme activity and complement C3 content in Nile tilapia, indicating a stronger immune response.
Additionally, certain fungi exhibit antimicrobial properties, providing an extra layer of protection against pathogens. Rhodotorula glutinis, for instance, has demonstrated antibacterial effects against Gram-positive bacteria, making it a valuable additive in aquaculture feed.
Challenges and limitations
Despite their benefits, the use of pigmented fungi in aquaculture faces challenges:
- Mycotoxin Risks: Some fungi can produce mycotoxins, toxic substances that affect fish health and food safety.
- Palatability Issues: High concentrations of fungi in feed may reduce palatability, decreasing consumption and growth.
- Production Costs: Large-scale production of pigmented fungi can still be expensive, limiting widespread adoption.
- Regulations: The lack of international standards and inconsistent regulations complicates the approval and use of these additives in different countries.
Conclusion
Pigmented fungi represent a sustainable and innovative solution for the aquaculture industry. By improving fish growth, pigmentation, and immune function, these microorganisms address key challenges in aquaculture while reducing reliance on synthetic additives.
Contact
Christina Zantioti
Laboratory of Applied Hydrobiology, Faculty of Animal Science, Agricultural University of Athens
Iera Odos 75, 11855, Athens, Greece
Email: zantioti.christina@aua.gr
Reference (open access)
Zantioti, C., Dimitroglou, A., Mountzouris, K.C. et al. Use of pigmented fungi as additives in aquaculture. Aquacult Int 33, 162 (2025). https://doi.org/10.1007/s10499-025-01840-0
