Imagine what kind of food will be on the next generation’s dining table. How different will it be from today’s? Currently, many types of food are available, and food is becoming more diverse than it was in the past. Novel food products are being developed through genetic modification techniques, new additives, and improved manufacturing techniques, such as frozen, canned, and fermented foods, to make them tasty, healthy, and safe. Moreover, considering the future global environment, it is necessary to increase the number of sustainable foods. Breakthroughs in food manufacturing are essential to achieve this goal.

The current problem we face in our dietary life is the “protein crisis.” It has been said that protein production will fall below consumption levels due to future world population growth and that protein will be in short supply by 2050. Meat is the main protein source in modern diets. However, conventional meat production hurts the environment because of methane gas emitted by animals, water consumption, and deforestation to obtain more space for farmland. To address this, research on alternative protein sources, such as plant-based, insect, and cultured meats, is accelerating. Recently, more attention has been paid to cultured meat, produced by culturing cells outside the bodies of livestock. Major public awareness of cultured meat came in 2013, with the presentation of a hamburger made from cultured bovine cells by Professor Mark Post of Maastricht University. The hamburger patty costs $300,000, making it a hot topic ¹.

If you try to make cultured meat from cultured cells, you will be surprised at how many cells are needed ¹. Producing large numbers of cells requires large volumes of culture media. Therefore, the culture medium accounts for most of the cost of producing cultured meat. Developing a cost-effective medium is important to deliver cultured meat to the table sustainably. In general, the culture medium contains nutrients derived from grains, supplemented with growth-promoting factors such as fetal bovine serum (FBS) or purified growth factors. One of the challenges today is that FBS and recombinant proteins are expensive and increase the cost of the culture medium. Several cultured meat production start-ups have now reduced the culture medium’s cost. Although details are not available, it was disclosed that the newly developed culture medium does not contain FBS ^{2, 3}. The Good Food Institute has published a white paper on how to lower the media costs of cultured meat production. This report also states that the key is reducing the cost of growth factors ⁴. 

Moreover, the environmental impact of consuming large amounts of culture media must be considered. Grains are the primary source of nutrients in culture medium. The use of grains as both food and animal feed competes with their use in culture medium production. Therefore, if large quantities of culture medium are produced, there is concern about grain shortage. Furthermore, the production of grains will increase the environmental impact, given the use of chemical fertilizers and pesticides derived from fossil fuels as well as deforestation. To avoid this problem, we prepared a medium using microalgae as the nutrient source instead of grains. Compared to grains, microalgal culture has a lower environmental impact owing to its high growth capacity, protein content, and CO₂ fixation capacity. Furthermore, it can be cultivated on land unsuitable for crops, so it does not compete with conventional agriculture. First, we successfully cultured animal cells in microalgae-derived nutrient medium and found that adding FBS increased the proliferation of bovine myoblasts ^{5, 6}.

Next, we focused on animal cell culture supernatant (conditioned medium; CM) as an alternative to FBS to improve the medium for more effective cultured meat production. CM, which in most cases is discarded after culture, is known to be rich in factors secreted by the cells that promote cell growth, such as cytokines and growth factors. We hypothesized that the supernatant of specific cells cultured in a culture medium consisting of microalgal nutrients could be beneficial for the production of cultured meat.

Thus, we designed the following medium production procedure (Figure 1), which we have shown in this study to be feasible:

1) Rat liver epithelial RL34 cells are ideal for harvesting supernatants rich in factors that promote the proliferation of bovine myoblasts, the primary cell source of cultured beef.

2) Chlorella vulgaris, a highly nutritious microalga, can be a nutrient source for bovine myoblasts and RL34 cells.

3) RL34 cells were efficiently cultured in a microalgae-based nutrient solution, and the supernatant contained growth factors. It was later confirmed that bovine myoblasts could be grown using the collected supernatant (Figure 8).

If cultured meat can be produced with nutrients from microalgae and growth factors secreted by the cells, it will be more sustainable than previously assumed.

Chlorella vulgaris is a food, and the culture supernatant produced in a sterile controlled environment guarantees the safety of cultured meat. Therefore, we are engaged in further research for practical applications to establish affordable, safe, and sustainable cultured meat as a new food and to build a stable food environment for the next generation.

1. Bodiou, V., Moutsatsou P., Post M. J. Microcarriers for Upscaling Cultured Meat Production, Front Nutr. 7, 10; 10.3389/fnut.2020.00010 (2020).
2. Mosa Meat, 2020/7/22: https://mosameat.com/blog/milestone-over-80x-reduction-in-our-medium-cost (2023/2/3).
3. UPSIDE Foods, 2021/12/9: https://upsidefoods.com/animal-component-free-upsides-cell-feed-breakthrough-levels-up-the-future-of-cultivated-meat/ (2023/2/3).
4. Spechit, L.: White Paper on The Good Food Institute, https://gfi.org/wp-content/uploads/2021/01/clean-meat-production-volume-and-medium-cost.pdf (2018).
5. Okamoto, Y., Haraguchi, Y., Sawamura, N., Asahi, T. & Shimizu, T. Mammalian cell cultivation using nutrients extracted from microalgae. Prog. 36, e2941; 10.1002/btpr.2941 (2020).
6. Okamoto, Y. et al. Proliferation and differentiation of primary bovine myoblasts using Chlorella vulgaris extract for sustainable production of cultured meat. Prog. e3239; 10.1002/btpr.3239 (2022).