Single-cell protein

Single-cell protein (SCP), or microbial protein, is made by growing microbes and eating the whole cell, usually dried. This is called biomass fermentation. Because the whole microbe is the product, processing is simpler than precision fermentation, which is why we think it is the best route for open source protein.

Replacing a fifth of the world’s ruminant meat with microbial protein by 2050 could halve deforestation, according to one model (Humpenöder et al., 2022).

Fungi (mycoprotein)

The most established form. Quorn has sold mycoprotein from Fusarium venenatum since the 1980s. ENOUGH makes it in the Netherlands, and Nature’s Fynd sells a related Fusarium in the US. Fungi are usually fed sugar.

Algae

Spirulina (Arthrospira platensis) is already sold as a supplement and has a slightly sweet, nutty taste; the European Space Agency has even proposed spirulina gnocchi for Mars. Strictly it is a cyanobacterium, so the risk of cyanotoxins has to be managed. Chlorella has less protein but doesn’t make cyanotoxins; Brevel, for example, grows it commercially. Algae grown in light need large surfaces to catch it.

Methane-eating bacteria

Methanotrophs make protein from methane, mostly for animal and fish feed so far. Calysta, Unibio (building a large plant in Saudi Arabia) and String Bio (India) are among the companies working on them.

Hydrogen-oxidising bacteria

Hydrogen-oxidising bacteria (HOB) make protein from hydrogen, oxygen and carbon dioxide, and the hydrogen and oxygen can come from splitting water with electricity, so they need no crops, sunlight or methane. That’s why we’re working on them; What is sustainable protein sets out the case and the challenges.

• Companies: Solar Foods (Finland) makes Solein from its proprietary strain, Xanthobacter sp. SoF1, which is approved in Singapore and sold in the US (Solar Foods). Air Protein (US) has also developed HOB protein. NovoNutrients (US) closed in 2025 after running out of money, as did Arkeon (Austria), which used hydrogen-oxidising archaea rather than bacteria to make amino acids (AgFunderNews).
• Cupriavidus necator is the best-studied HOB; the genomes of two strains are published (Angenent et al., 2022).
• Non-profit and public research: ALLFED has studied HOB for food resilience, and the Nordic HERO-Protein project runs to 2028.

Like all bacterial protein, HOB biomass is high in nucleic acids, which have to be reduced before it is eaten in quantity, and some HOB carry endotoxins in their cell walls (Angenent et al., 2022). Working these out in the open is part of what we do.