CRISPR-edited fungus boosts protein production and cuts environmental impact

In a new study publishing November 19 in the Cell Press journal Trends in Biotechnology, researchers used a gene-editing technology called CRISPR to increase a fungus's production efficiency and cut its production-related environmental impact by as much as 61%-all without adding any foreign DNA. The genetically tweaked fungus tastes like meat and is easier to digest than its naturally occurring counterpart. 

There is a popular demand for better and more sustainable protein for food. We successfully made a fungus not only more nutritious but also more environmentally friendly by tweaking its genes." 

Xiao Liu, corresponding author, Jiangnan University, Wuxi, China

Animal agriculture is responsible for about 14% of global greenhouse gas emissions. Raising livestock also takes up land and requires a large amount of fresh water, which is already at risk due to climate change and human influence. Microbial proteins, including those found in yeast and fungi, have emerged as a more sustainable alternative to meat. 

Among the options explored thus far for mycoprotein, or fungi with protein, the fungus Fusarium venenatum stands out because of its natural texture and flavor, which closely resemble those of meat. It has been approved for food use in many countries, including the United Kingdom, China, and the United States. 

However, Fusarium venenatum has thick cell walls that make its nutrients difficult for humans to digest. Also, it's resource intensive; producing even small amounts of mycoprotein requires a large amount of resource input. The spores are raised in giant metal tanks filled with feedstock made with sugar and nutrients like ammonium sulfate. 

Liu and his team set out to explore the potential of boosting Fusarium venenatum's digestibility and production efficiency using CRISPR-without introducing foreign DNA into the fungal genes. 

To do so, they removed two genes associated with the enzymes chitin synthase and pyruvate decarboxylase. Eliminating the chitin synthase made the fungal cell wall thinner, allowing more protein inside the cell to become available for digestion. Taking out the pyruvate decarboxylase gene helped to fine-tune the fungus's metabolism so that it required less nutrient input to produce protein. 

Analyses showed that the new fungal strain, dubbed FCPD, required 44% less sugar to produce the same amount of protein compared to the original strain and did so 88% faster. 

"A lot of people thought growing mycoprotein was more sustainable, but no one had really considered how to reduce the environmental impact of the entire production process, especially when compared to other alternative protein products" says first author, Xiaohui Wu of Jiangnan University. 

The researchers then calculated the environmental footprint of FCPD, from spores in the laboratory to inactivated meat-like products, at an industrial scale. They simulated FCPD production in six countries with different energy structures-including Finland, which uses mostly renewable energy, and China, which relies more heavily on coal-and found that FCPD had a lower environmental impact than traditional Fusarium venenatum production did, regardless of location. Overall, FCPD production resulted in up to 60% less greenhouse gas emissions for the entirety of its life cycle. 

The team also investigated the impact of FCPD production compared to the resources required to produce animal protein. When compared to chicken production in China, they found that myoprotein from FCPD requires 70% less land and reduces the risk of freshwater pollution by 78%. 

"Gene-edited foods like this can meet growing food demands without the environmental costs of conventional farming," says Liu.