Apparently a hydrogen-oxidising bacterium known as Cupriavidus Necator, per https://allfed.info/images/pdfs/Food_in_space_from_hydrogen_...

(I would never have found this before AI search)

It says that it's a biorecator:

"To put that in perspective, Solar Foods explains that the newly-built factory’s bioreactor can grow the same amount of Solein protein per day as a 300-cow dairy farm would produce milk protein"

Is your complaint that they don't specify the micro-organism?

Yes. Bacteria? Fungi? Yeast? Algae? GMO hybrid of all four? It's weird. Are they even going to tell the customers? I didn't find a single clue online.

Well they say "Solein, protein out of thin air, is not a plant nor an animal. It originates from a natural, non-modified, single-cell organism" so my guess is that the specific micro-organism is a trade secret to protect their business, not because it's like, people. But you could always email them to ask. Maybe it is people.

Human stem cells are pretty easy to make now, so...

Solein Green

Solein Green