Gene Alteration of Mushrooms for Better Plant-Based Meat

Bioengineers produce a plant-based protein with a fraction of the environmental impact of meat by altering mushroom proteins.

By Adelaide Levenson

The switch from animal products to plant-based alternatives has grown rapidly over the last decade. More and more individuals are becoming vegetarians or vegans, or they’re swapping out some of their animal products for plant-based ones. New products frequently hit the shelves, from plant-based deli slices and burgers to ice creams and cheeses, each an improvement over the last version. A large portion of this industry is made up of meat alternatives; these faux “meat” products are commonly made up of protein from peas, soy, wheat, and other plants. While these options grow in number, we can turn to biotechnology to expand the products even further. Using genetically engineered mycoproteins (protein from mushrooms or molds), we can tailor the taste and texture of meat alternatives while also producing a product that requires less processing than other options. 

The Benefits of Eating Plant-Based

Our global food system has a significant impact on climate change. It is estimated that around 15 percent of greenhouse gas emissions are a result of animal agriculture. The process of raising livestock for food requires large amounts of water and land, and it produces high quantities of both methane and nitrous oxide, gases that are detrimental to the atmosphere. A 2018 study looked at the amount of greenhouse gases produced per 1 kg of food product. The researchers found that the emissions from beef cattle were over 30 times greater than that of tofu (soybeans). Additionally, a Life Cycle Assessment also reported that, by 2050, some greenhouse gas emissions and deforestation could be reduced to half by substituting just 20 percent of animal protein with mycoprotein. Therefore, the transition from animal agriculture to alternative, plant-based methods will positively impact the environment. 

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While many meat alternatives have been explored already, mycoproteins are lacking in breadth. Mycoprotein is made from filamentous fungi, which include molds and mushrooms, and are already commonly used in fermented foods. Biomass from mushrooms, also known as mycelium, can be used in meat alternatives to produce textures that are similar to the real thing. This is possible because their structure is able to mimic that of animal muscle.

While there are currently fungal replacements for meat and dairy products on the market, they are restricted to non-engineered strains. These non-engineered strains are limited by their structure and industrial capacity, a challenge that could be overcome with the use of bioengineering. For example, recently an industrial fungus for enzyme production, Trichoderma reesei, was able to produce egg white and milk protein on a gram scale as a result of synthetic gene expression. Although this was a feat in the industry, the fungus does not have a history of safe and palatable consumption and therefore prohibits its applications within food.

Expanding synthetic biology tools can allow for food-safe, edible fungi to extend to food production. These tools have the potential to enhance fermented foods and produce mycoprotein that is more suitable for dietary needs and preferences. This outlook emphasizes the need for the use of biotechnology in the realm of food production.

The Tool(set)s for Alternative Meat Production 

Researchers based out of University of California, Berkeley, recently published their study on how they set out to develop the tools needed to engineer any fungi into a viable strain for meat alternatives. Their developed tools include (1) a CRISPR-Cas9 method for gene modification, (2) neutral loci for targeted gene insertion, and (3) tunable promoters. The researchers tested their toolset on Aspergillus oryzae (koji mold). This fungus was chosen due to its long history of safe use and acceptance in fermented food, as well as its umami flavor and high amount of protein.

Using the CRISPR-Cas9 method (1), the researchers modified genes of the koji mold to make them palatable for consumers. With the neutral loci (2), they determined the location of gene clusters that are not important for the function of the fungi. Then, they used those locations to insert artificial genes into the organism. Finally, tunable promoters (3) were used for gene regulation. Specifically, they decided upon a bidirectional promoter, which can be used to speed up the process of genetic engineering. Overall, the goal of this toolkit is to edit the fungi’s nutritional value and sensory appeal as an alternative meat.

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When it was time to test out their toolkit on the koji mold, the researchers began by making it overproduce heme. Heme, an iron-based molecule, is responsible for the color and flavor in red meat. The team of scientists also wanted their mycoprotein to overproduce ergothioneine. Ergothioneine, a sulfur-containing antioxidant, was previously determined to be an anti-inflammatory agent. Other modifications to the koji mold included altering the molecular composition and appearance. 

This toolset lays the groundwork for the increase of mycoprotein products going to market. Although this work is in its early prototypes, it’s an exciting development for the plant-based community. The future of bioengineered fungi includes improvement of flavor, nutrition, and textures. Having the biological tools to edit the genes of fungi can make them more palatable and nutritious. This is a promising avenue for alternative meat products and you should keep an eye out for mycoproteins in your local grocery store!

It’s important to note that you don’t need to confine yourself to a specific label like vegetarian, vegan, plant-based, etc. Occasionally swapping out an animal product for a plant-based one also makes a difference. There are tons of delicious plant-based products with a large range on the market—there’s something for everyone!

This study was published in the peer-reviewed journal Nature Communications.

References

Humpenöder, F., Bodirsky, B. L., Weindl, I., Lotze-Campen, H., Linder, T., & Popp, A. (2022). Projected environmental benefits of replacing beef with microbial protein. Nature 605, 90–96. https://doi.org/10.1038/s41586-022-04629-w

Maini Rekdal, V., van der Luijt, C. R. B., Chen, Y., Kakumanu, R., Baidoo, E. E. K., Petzold, C. J., Cruz-Morales, P., & Keasling, J. D. (2024). Edible mycelium bioengineered for enhanced nutritional value and sensory appeal using a modular synthetic biology toolkit. Nature Communications, 15(2099). https://doi.org/10.1038/s41467-024-46314-8

Ritchie, H., Rosado, P., & Roser, M. (2022). Environmental impacts of food production. Our World In Data. https://ourworldindata.org/environmental-impacts-of-food

Solomon, T., Gupta, V., & Ncho, C. M. (2023, November 22). Environmental impacts of livestock production. Scholarly Community Encyclopedia. https://encyclopedia.pub/entry/51867

Featured image “lawn fungi” by planes, space, nature is marked with Public Domain Mark 1.0.

About the Author

Adelaide Levenson is a chemist and baker with a passion for science communication. She recently received her MSc in chemistry with a specific focus on polymers, and currently resides in Germany.