Air-Based Protein: Sustainable Food, Courtesy of Bacteria

Klara Zietlow
11 min readOct 25, 2021


Deeelicious chicken I Unsplash

By now, most people know that our current methods of protein production suck. 660 gallons of water for a burger? Two tanks of gas for a steak? Killing baby animals? 🥺

With all this talk about going vegetarian for the environment, it’s clear meat is very harmful to the earth. Yet, plant based proteins aren’t great either.

Take soy for example, it has been associated with slavery, rainforest deforestation, and is a monoculture meaning it is more vulnerable to disease and contributes to biodiversity loss.

Even though plants use less land and water than animals, they still use an absurd amount. Half of all habitable land is used for agriculture!

Our World In Data

This is because of the 10% rule: only 10% of the energy an organism receives will be turned into biomass.

Water and land are two of our planet’s most valuable resources. With this inefficiency, they’d be much better spent on ourselves than our food.

But, if animals are bad and plants are bad too, what are we going to do? Make protein out of air?


Say Hello to Hydrogen Oxidizing Bacteria

There is a method of producing food with single cell proteins. Single cell proteins (SCP) come from microbial cultures like algae, fungi, yeast, and bacteria which are naturally high in protein.

A cute plate of SCP I Padeepz

Hydrogen oxidizing bacteria can produce nutritious biomass out of, you guessed it, hydrogen!

With this process, they’re 20x more efficient than photosynthesis and 200x more efficient than meat.

It gets better; If renewable energy and direct air capture (DAC) is used to supply the bacteria with nutrients, the entire process would be carbon negative. Take that cows!

What Is This Magic Bacterium?

Hydrogen oxidizing bacteria (HOB), sometimes called knallgas bacteria, are unique in that they can use oxygen as an electron acceptor and hydrogen as an electron donor to fix CO2, increasing their biomass. As their biomass increases, so does their protein content. 💪

Being bacteria, they don’t need a whole lot to make protein; no crops, no sun, no pollination. All these guys need is some CO2, H2, O2, and a mineral salt medium containing essential nutrients like nitrogen, phosphorus, and sulphur.

HOB are usually aerobic, meaning they need oxygen to survive. They get their energy from chemosynthesis–the conversion of carbon molecules into organic matter through the oxidation of inorganic compounds.

From Bacteria to Food

Obviously, we’re not just going out into the forest, plucking up some dirt, and calling it a day. ‘Wild-Harvested Bacterial Protein,’ am I right?

In order for this to be commercially feasible, all of the nutrients would be fed into a giant bioreactor along with the bacteria for cell growth to happen. Inside there, the HOB convert the raw inputs into protein-packed biomass with a byproduct of oxygen.

Amazing diagram from this paper

The fermentation broth itself is only around 1–3% bacterial cells & unused nutrients. The rest is water. This is because hydrogen has a lot of energy and when combined with oxygen, the energy is freed to be used by the bacteria. When this happens, some of it becomes biomass but a lot is converted back into water.

So It’s Organic and Gluten-Free…But Is It Local? (aka feedstock origins)


Different species of HOB are found all around the world in places like sludge, soil, and hydrothermal vents. For food production, many types could work but I’ll use Cupriavidus necator for any statistics in this article because it has been studied well.

Dr. Arjan Pol collecting from a mud pool near Naples I Nature


Hydrogen is the most abundant element on Earth, just a little hard to get to.

Some ways of accessing it are gasification of solids, capturing it as a waste product from the chemical industry, or steam methane reforming. Here’s why none of those are great options:

  • Gasification of solids would most likely be of coal which is dirty and bad for the environment
  • Getting hydrogen as a waste product is complicated and less readily available/evenly distributed
  • Some microbes are already able to make single cell proteins out of methane so it would make more sense to use these instead of turning it into H2 for HOB (Check out Mango Materials’ methanotroph bioplastic!)

This leaves us with electrolysis for getting our hydrogen.

Fancy new method of electrolysis using PV cells by EPFL I

Right now there’s much debate over whether in-situ electrolysis (performed inside the bioreactor) is the best option or external electrolysis.

In-situ electrolysis uses less energy and is more convenient since the resulting gases don’t need to be transported to the bioreactor. It’s also safer than external electrolysis just because of the lower likelihood of combustion if flammable mixtures (H2 & O2) are ignited by measurement instruments while being pumped into the bioreactor.

So this doesn’t happen 😉

BUT, since trying to perform electrolysis in a bioreactor full of hangry bacteria is quite new, scientists need to make sure no toxins from electrodes or salts are dissolved into the fermentation broth. Scientists also need to experiment to find the perfect balance between a suitable environment for bacteria and the efficiency of the electrolysis.

Electrolysis on its own is already a well researched process so for now it may make more sense for the two to remain apart, but I think once the idea of HOB for food becomes more common, in-situ electrolysis will be the way to go.

If it gets to the point where it’s safe and just as effective, it would require less capital and could be optimized for the specific purpose of feeding HOB. This already is the method preferred by startup Solar Foods in Finland.

Carbon Dioxide

One exciting aspect of air-based protein is that it can run on CO2 captured via direct air capture (DAC).

Does this mean we can eat our way out of climate change? I Giphy

For DAC, air gets passed through either a solid or liquid medium where CO2 gets caught. Once energy is added, CO2 gets released and can be collected. This is called absorption if it’s liquid based or adsorption if it’s solid.

It’s also possible to use atmospheric air instead of going through all this DAC stuff but the electricity to biomass efficiency of the bacteria dropped from 54% to 20% compared to when they were fed 100% CO2 which can be achieved with DAC.


This just comes from electrolysis.


Nitrogen can come from ammonia from the fertilizer industry.


Now that we know the bacteria are indeed fed the finest local ingredients, let’s move on to what happens after they’ve grown big and strong. This by the way is super quick (only a few hours)!

With the nutrients converted into biomass, the bacteria need to be processed into a consumable form.

This is tricky since bacterial cells are teeny tiny, only 1–2 μm in diameter. On top of that, their density is similar to that of water.

Amazing diagram from this paper

The post-processing steps differ by use case but usually include flash evaporation and heat treatment to remove water & kill bacteria, centrifugation (or less commonly, a membrane for microfiltration), homogenization or grinding for consistency, and spray drying (think of cheese powder 😉).

Now is also when the nucleic acid would be removed. HOB’s high nucleic acid content isn’t a problem for cows and other ruminants but can give humans gout and kidney stones if over consumed. We can’t have >2 g. per day.

To remove it, the cell walls (which humans can’t digest anyways) are destroyed which causes the nucleic acid to leach out.

At this point, the bacteria can be stretched even further and undergo solvent extraction to remove lipids and polyhydroxyalkanoates (PHA) from the protein fraction which can be used in plastic.

PHA’s many, maaany use cases I SpringerLink

Bacteria > Soylent (+ Veggies + Fishies)

Let’s start with protein, since that’s what this article’s about. C. Necator has a 50–65% dry weight protein content which is impressive compared to soy’s 35–38%. It even stands up to beef, which is ~65%!

This number can go way up with a bit of artificial selection or genetic modification. For example, Air Protein’s HOB strain is a whopping 80% protein!

Air Protein’s magic powder I The Spoon

These hardworking bacteria offer so much more than just protein though. They contain an amino acid profile comparable to animal protein and double that of soy protein.

The end protein powder is rich in vitamins and minerals and jam packed with nutrients including many B vitamins–niacin, thiamin, riboflavin, B6, and even B12, which is hard to get on a plant-based diet.

Unlike many protein sources which have distinct flavors, bacteria don’t taste like much, meaning they have the potential to be found in a variety of grocery aisles. Pasta, bread, fake meat, drinks, or even a straight protein powder are all possible!

Solar Foods’s “Solein” Meatballs I Sifted

If it’s produced for animal feed, it can function just like soy protein and fishmeal do today and no new processes would need to be developed.

Statistics to Make You Scream (With Joy)

Bacterial protein production would use 2,000x less water than soy and only 10% of the land area per year than the same amount of soy protein would over a year.

According to Air Protein, they can make the same amount of protein on a production facility the size of Disneyworld as they would be able to on a soy farm the size of Texas.

If clean energy sources become more space-efficient in the future, this number will drop even lower!

Then there’s time. Protein made from HOB only takes a couple of days until it’s ready for harvest. That’s compared to 3 months for soy, 5 months for chickens, and 2 years for a cow!!

And, if produced via continuous processing, you’ll have a never ending reliable protein source.

In case you can’t comprehend how insane that is.

As the effects of climate change loom before us, microbial proteins are a great way to ensure we still have the ability to feed everyone in the case of a catastrophe. Since it’s a closed system, the weather has no impact and the system can reuse nutrients to their fullest potential.

No pesticides or herbicides are used either, protecting biodiversity.

What I find the coolest thing is that it can be grown anywhere: the desert, the arctic, a remote island. Currently our food system is confined to the 37.7% of Earth’s land that has the potential to be farmed, according to the World Bank. With HOB, we could even be making food in space!

A cosmopolitan bacteria indeed.

Finally, research by RethinkX predicts protein from precision fermentation will be 10x cheaper than animal protein by 2035.

So Why Don’t I Eat This Yet?

The biggest hurdle that the technology faces is the cost of electricity used during electrolysis. 90% of all the energy used during the process is for that part. Right now, just the energy used costs more than the price of soy!

The bacteria are hardy enough to survive night cycles without electricity when solar energy isn’t available, but honestly the only thing that would make a difference is the electrolysis.

Then there’s sterility because bioreactors are a nice environment for many microorganisms, not just the ones we want and the toxicity risk from the electrodes brought up earlier.

If only this worked for bioreactors… I Giphy

Not to mention the labor intensive process of finding the best strains. Selecting or modifying HOB (which comes with its own set of ethical & legal issues) is labor intensive and experiment based. This is a slow process and there’s a lot of ways things could go wrong.

One way this could be overcome is by sequencing the potential bacterium’s genome, but right now that’s still too expensive to do on a large scale.

Finally, there’s the whole stigma and “It’s not natural! Ahhh!” The whole reason I learned about air-based protein in the first place is through an article from a woman who had heard about it at a conference and was scared of it.

I believe that over time people will become used to the idea. Quorn is a company making SCP alt. meat. Their mycoprotein (fungi) is made very similarly to the HOB process described and is super popular around the world!

A platter of Quorn meatless pieces I Quorn

Another example: nutritional yeast (aka nooch). You may know it as that stuff your hippie aunt puts on the table instead of parmesan, but recently nooch has been getting a lot of attention as the key to perfect vegan mac and cheese — or anything umami really.

Nooch is made through almost the exact same process as air-protein: cultivation in a bioreactor & post-processing. AND NOBODY CARES!!

The key to perfectly cheesy popcorn I Yummly

To the “it’s not natural” argument: What is natural?

If you travelled back in time to visit a hunter-gatherer and put a modern ear of corn in their hand, would they even know what it was?

Today, everything in our food system comes from the clever manipulation of living organisms. There’s no reason why this is any less natural than what we’re already eating. And remember, it’s not like we invented these bacteria. They have been surviving like this on their own for ages; all we’re doing is providing a house to live in.

Looking Forward

Looking forward to eating HOB like a sunset trip on the Titanic (minus the iceberg) I Giphy

If we can overcome these hurdles, we have a very bright future ahead of us. The microbial protein industry is still small and the HOB industry is just miniscule. Air Protein (my article) and Solar Foods are working on bringing this for human consumption and NovoNutrients is making this a reality for animal feed.

These startups all have great teams of people and investors supporting them so I have high hopes for the future of air-based protein. If you’d like to learn more, check out my favorite papers below:

If you made it all the way down here, thank you!! I’m Klara, a 14 year old super passionate about the future of food and sustainability.

I’d first like to give two huge shout outs to Juan B. García Martínez and Jani Sillman for their help answering my questions. They’re also both wonderful authors and wrote some of the papers above 😀

If you’d like to learn more about me, you can visit my personal website or LinkedIn. Make sure to follow me here on Medium too for updates on articles I publish. Thank you for your support :)



Klara Zietlow

Passionate about the future of food and the environment. Likes animals too :)