Breeding Success in Diatoms with Enhanced Levels of Five Functional Fatty Acids Including DHA and EPA

Key Points of the Announcement:

We have succeeded in breeding diatoms, which are globally important as aquaculture feed, to simultaneously increase the content of functional fatty acids important for feed, such as DHA and EPA, by up to 1.8 times per cell.

This allows for a significant increase in multiple fatty acids without the decline in fatty acid balance in feed, which is a problem with conventional breeding methods that increase specific fatty acids like DHA and EPA.

By utilizing these diatom strains as raw materials with high functionality, we aim to accelerate the development of aquaculture feed that replaces fishmeal and fish oil, and realize sustainable fisheries.

NTT Corporation (Headquarters: Chiyoda-ku, Tokyo; President and Representative Director: Akira Shimada; hereinafter referred to as "NTT") has succeeded in breeding diatoms that simultaneously enhance the content of five functional fatty acids, including DHA and EPA, which are important for aquaculture feed, through its proprietary breeding technology. Previously, there was a challenge where increasing specific fatty acids would disrupt the balance with other fatty acids. However, this achievement makes it possible to improve the levels of multiple important fatty acids without compromising that balance. This outcome will promote the practical application of algae-derived feed ingredients and serve as a foundation for the development of sustainable aquaculture feed that does not rely on fishmeal or fish oil.

Figure 1. Characteristics of Algae-Alternative Feed, Challenges in its Research and Development, and an Overview of This Achievement

1. Background Currently, driven by global population growth and changes in dietary culture, the demand for aquatic products continues to expand. On the other hand, environmental changes such as global warming are making fishing, which relies on natural resources, increasingly unstable. Amidst this situation, aquaculture production of aquatic products has expanded rapidly, and it is said to account for approximately 60% of global aquatic product supply (Note 7). Feed is indispensable for aquaculture, but many of its main ingredients, fishmeal and fish oil, are derived from small wild fish. Small fish are crucial organisms that support marine ecosystems, and their excessive use leads to increased environmental load. Against this backdrop, the development of sustainable feed ingredients to replace fishmeal and fish oil is urgently needed. Algae called diatoms are one promising candidate as they can be produced without relying on natural biological resources and generate functional fatty acids such as DHA and EPA, which are important for aquaculture feed. However, to practically utilize diatoms as alternative ingredients, it is necessary to further increase the content of these fatty acids. This research aimed to solve this problem by breeding diatoms that can replace fishmeal and fish oil.

2. Key Points of This Technology Heretofore, diatom breeding research has primarily focused on attempts to individually increase the amounts of specific fatty acids like DHA and EPA using genetic engineering techniques. On the other hand, it is generally known that the processes by which fatty acids are produced within cells are interrelated, and increasing specific fatty acids can affect the amounts and composition of other fatty acids. As a result, concerns arise about the disruption of the balance as feed. In this study, we targeted *Chaetoceros gracilis* (Note 8), a marine diatom widely used as feed in aquaculture. By introducing genetic mutations (Note 9) into this diatom using NTT's proprietary technology and newly establishing selection criteria that are not limited to specific fatty acids, we obtained candidate strains.

Figure 2. Diatom Strain Breeding Flow

3. Breeding Achievements Analysis of the fatty acid composition and content of the obtained candidate strains revealed that, in addition to DHA and EPA, which are important fatty acids for fish and shellfish, the content of multiple functional fatty acids involved in growth and physiological functions, such as alpha-linolenic acid (Note 10), dihomo-gamma-linolenic acid (Note 11), and linoleic acid (Note 12), was simultaneously increased, achieving up to a 1.8-fold increase per cell. Furthermore, these bred strains do not utilize genetic engineering technology and are therefore not subject to regulations imposed on genetically modified organisms. Consequently, the hurdles for commercialization, such as review and notification processes, are significantly reduced, making them highly suitable for practical application and social implementation.

Figure 3. Comparison of Fatty Acid Synthesis Amounts in Parent and Bred Strains

4. Future Developments The diatom strains bred this time are important materials that will promote the transition from feed dependent on natural resources to sustainable feed. In the future, we will accelerate the performance evaluation of feed using these algae. Furthermore, since the fatty acids increased in these diatom strains are also important for high-functionality supplements, their application is expected in a wide range of fields beyond aquaculture feed. This breeding technology is also considered applicable to other algae as a common platform for enhancing algal nutritional value. By expanding the range of target algal species and developing new applications, we will broaden their use as high-functionality materials in various industries and contribute to further reduction of environmental impact.

5. Related Past Press Releases * November 12, 2021: NTT and Regional Fish Begin Demonstration Aiming to Reduce CO2 in the Ocean ~World's First Application of Genome Editing Technology to Carbon Circulation in Algae and Aquatic Organisms in an Environmentally Neutral Ecosystem~ * February 9, 2023: Gene Identified that Dramatically Improves CO2 Absorption by Algae * July 4, 2024: World's First Establishment of Algae Variety Improvement Technology Using Neutron Irradiation ~Success in Increasing Oil Production by up to 1.3 Times for Biofuel Feedstock~

[Glossary] * Note 1. Diatoms: A group of algae that are said to contribute up to 20% of the Earth's total primary production. In the aquaculture industry, they are widely used mainly as feed during seed production. * Note 2. DHA: Docosahexaenoic acid. A fatty acid involved in the growth, immune function, and stress response of fish and shellfish. * Note 3. EPA: Eicosapentaenoic acid. A fatty acid involved in the growth, immune function, and inflammatory response of fish and shellfish. * Note 4. Functional fatty acids: Fatty acids that exhibit regulatory effects in the body and may be involved in maintaining health and preventing/improving diseases. * Note 5. Breeding: The process of improving organisms for human benefit by utilizing changes in their characteristics due to genetic alterations. * Note 6. Strain: Refers to a collection of organisms of the same lineage, such as microorganisms and microalgae. * Note 7. The State of World Fisheries and Aquaculture 2024 * Note 8. *Chaetoceros gracilis*: A single-celled planktonic diatom known as the bristly-spined diatom, used worldwide as feed for juvenile shrimp and bivalves. * Note 9. Genetic mutation: A state where the base sequence of DNA constituting a gene differs from the original sequence. As a result of a genetic mutation, the function of the protein produced from the gene is altered. * Note 10. Alpha-linolenic acid: A fatty acid used in the synthesis of DHA and EPA, playing a supplementary role in compensating for their deficiency. * Note 11. Dihomo-gamma-linolenic acid: A fatty acid that has been increasingly studied in recent years, with research in humans suggesting potential anti-inflammatory and anti-allergic effects. * Note 12. Linoleic acid: A fatty acid involved in the growth and lipid metabolism of fish and shellfish.