Power-to-Protein: Scientists use microbes to turn CO2 into yeast rich in protein and vitamin B9

16 Sep 2024 --- Germany-based researchers designed a two-stage “Power-to-Protein” bioreactor system that converts hydrogen, oxygen and CO2 into yeast rich in protein and vitamin B9 and runs on renewable energy. Only six grams or 0.4 tablespoons of the harvested dried yeast meets the daily vitamin B9 requirement, and 85 g or six tablespoons of yeast provides 61% of daily protein needs. 

In the first stage of production, the bacterium Thermoanaerobacter kivui converts hydrogen and CO2 into acetate, which is found in vinegar. Baker’s yeast, or Saccharomyces cerevisiae, feeds on this acetate and oxygen to produce protein and vitamin B9. The hydrogen and oxygen can be made by “zapping water with electricity” from clean energy sources such as windmills. 

Largus Angenent of the University of Tübingen, Germany, tells Nutrition Insight that the study demonstrates that “alternatives for animal-based protein do not just consist of plant-based proteins, but that we can produce protein with bioreactors, like what we do when we brew beer.” 

“Using bioreactors, we can completely uncouple nutritious protein production from land use. This, in turn, can reduce the competition between land for agriculture and nature. This is especially important in a country like the Netherlands.”

“The advantage of producing proteins in bioreactors is that we can fortify them with natural micronutrients, such as vitamin B9, shown in this study, in a targeted and simple way, thereby improving the population’s nutritional status,” adds the study’s lead author Lisa Marie Schmitz, also from the University of Tübingen. 

Sustainable production

The researchers note that the new technology, presented in Trends in Biotechnology, aims to address several global challenges, such as environmental conservation, food security and public health. The system reduces carbon emissions in food production by running on clean energy and CO2. 

Moreover, it frees up land for conservation by “uncoupling land use from farming.” At the same time, Angenent stresses that the system would not outcompete farmers. 

The two-stage bioreactor converts hydrogen, oxygen and CO2 into yeast rich in protein and vitamin B9 (Image credit: Lisa Schmitz).“We only produce protein and some vitamins,” he illustrates. “Farmers would need to produce other foods like grains and vegetables, fruit and plant-based proteins, more sustainably. Then, we would need more farmers per current productivity.”

“We do not want to replace farmers, but the agricultural sector would need to change to become sustainable and to improve soil health.”

“The fact that we can make vitamins and protein simultaneously at a pretty high production rate without using any land is exciting,” says Angenent. “The end product is vegetarian or vegan, non-GMO and sustainable, which could appeal to consumers.”

Micronutrient-enriched protein alternative

The technology may help countries globally overcome food scarcity and nutritional deficiencies by delivering protein and vitamin B9, making agriculture more efficient.

“We are approaching ten billion people in the world, and with climate change and limited land resources, producing enough food will become harder and harder,” says Angenent. 

The researchers note that while 85 g of yeast provides 61% of daily protein needs, these levels are much lower in traditional sources, such as 85 g of beef (34% of daily needs), pork (25%), fish (38%) and lentils (38%). 

However, they caution that the yeast needs to be treated to rid compounds that increase the risk of gout if consumed excessively. Treated yeast still exceeds traditional sources at 41% of daily protein requirements. 

Angenent notes that the yeast would end up in “food products that people would like to buy,” to which manufacturers could also add vitamins from other sources. “For example, 6 g of our dry yeast to a food product could satisfy an average person’s daily (vitamin B9) need.” 

Commercial development

The team aims to make the yeast a commercial protein alternative by optimizing and scaling up production, investigating food safety, conducting technical and economic analyses and determining market interest. 

To make the yeast a viable commercial alternative, the team aims to optimize and scale up production.“We are scaling up the system from 2-L bioreactors to 100-L bioreactors,” details Angenent. “We need to continue to measure the nutritional value, including the amino acid composition. We may need to find new yeast strains and know if customers would accept our product.” 

In addition, he notes that the team needs to create food from this protein source that people like to eat: “Taste and smell are important for our product.” 

Moreover, the team needs to understand the regulatory landscape and scale further to a commercially viable scale. 

“If we can produce in bulk volumes, then the price could decrease, but the protein quality may be more important. Not every protein is of the same quality, and yeast proteins may smell and taste better, so its price would be higher. But this needs to be investigated in detail,” projects Angenent. 

He also considers the potential to produce different vitamins using the new technology, which needs to be assessed. The researchers note that they should “only procure specific vitamins necessary to enhance the sustainability of this approach further and reduce the costs of the overall process.” 

“We could genetically modify the yeast to produce vitamins currently not made by the yeast. But this would not be viable in societies where genetically modified foods are not accepted,” Angenent explains. 

By Jolanda van Hal