A flurry of startups has sprung up in recent years using fermentation to coax microbes to produce more sustainable, functional, or healthier alternatives to animal and tropical fats (coconut, palm, cocoa).
Right now, most of them are feeding their microbes sugars, which are not cheap, use up agricultural land, and present major challenges if you want to operate a continuous fermentation process, says Dr. Shannon Nangle, cofounder at Cambridge, Massachusetts-based Circe.
Nangle, by contrast, is feeding her microbes carbon dioxide, hydrogen, and oxygen in a gas fermentation process completely decoupled from agriculture. And at scale, she claims, it could produce tailored fats that are cost competitive with dairy fats, cocoa butter and palm kernel oil.
AgFunderNews (AFN) caught up with Nangle (SN) pictured below at the company’s new pilot-scale gas fermentation facility in Waltham, Massachusetts, to find out more.
AFN: What’s the origins story of Circe?
SN: I always wanted to develop a technology that was able to transform ubiquitous raw materials into a laundry list of products and have that technology be used for extreme resource efficiency on Earth and in space. I basically wanted to make a replicator from Star Trek!
Circe spun out of my postdoc research at Pam Silver’s lab at Harvard in 2021. At that stage, we had demonstrated it was possible to make triglycerides from CO2, but still needed to climb the mountain of making a commercially viable strain [of bacteria] with meaningful productivities.
AFN: What makes gas fermentation exciting to you?
SN: We’re talking about scaling the manufacturing of all kinds of products at meaningful volumes to create essential products from a resource that the more we use of it [waste CO2] the better. It’s as close to a limitless form of manufacturing as you can get, so to me, that is worth pursuing as aggressively as possible.
But it’s also deployable at small scale, which takes me back to Star Trek…
As Calysta said, with gas fermentation, you can also run longer campaigns than companies doing fermentation with sugars, as you don’t have to worry so much about contamination [from unwanted microbes that will compete with your core microbe and eat your feedstock, limiting fermentation times]. You can run a more continuous process, which means you can decrease unit costs through the operation of the process. The feedstock is also cheaper [than purified sugars].
AFN: What microbes are you using?
SN: We’re using a bacterium, a soil microbe that naturally likes to make PHAs [biodegradable plastics produced by microorganisms] and engineering in it the ability to make triglycerides.
Whereas some other gas fermentation companies [such as Calysta and Solar Foods] are growing the cells as product, we are doing precision fermentation and genetically engineering microbes to produce mimetics of dairy fats or palm oil fractions, and then extracting them from the organism.
AFN: What gases do your microbes need?
SN: Our organisms need carbon dioxide, oxygen, and hydrogen. As we’re doing aerobic fermentation, the presence of oxygen is the real game changer here. Gas fermentation companies such as LanzaTech and Calysta use an anaerobic process because the organisms they use can eat carbon monoxide or methane and they’re really good at making simple hydrocarbons where you can optimize a wild type [Non GMO] organism to get great productivity.
We have an aerobic organism that can eat gases, which is rare, and kind of brings the best of both worlds. You can engineer it like heterotrophic sugar eating organisms [to make it produce your target ingredients] but it also unlocks the scale and low cost feedstocks that gas fermentation offers.
AFN: How are you sourcing these gases at the moment?
SN: Our optimistic goal is for our CO2 to be coming from the atmosphere [such that Circe is actually removing waste CO2 from the environment], and for our hydrogen and oxygen to come from electrolysis [splitting water into its constituent parts] powered by renewable energy.
Right now, that is possible, but not economical, so we have to go down the path of what are the most economical source of these gases right now. So for hydrogen, we ultimately want to use green hydrogen, but right now we can use gray or blue sources from something like steam methane reforming, with or without carbon capture. And then our CO2 is likely to come from a biogenic source [from a biological process rather than fossil fuels] such as ethanol refineries or breweries.
AFN: What about water and land use?
SN: The land use is minuscule and we can recycle up to 95% of the water at scale.
AFN: Aren’t some of these gases flammable?
SN: Yes, but there are well established protocols to handling hydrogen and oxygen together, mainly in the gas industry, so we actually end up looking more like an oil and gas process when it comes to safety.
AFN: What factors into the design of bioreactors for gas fermentation?
SN: You want small bubbles so as much surface area as possible of the liquid has contact with the gases so the organisms can get the gases into the cells. And then you want to allow them as much time with the gases as possible. So your objective is to get as much gas into the media as you can and there are multiple ways you can do that, whether that’s with temperature, pressure, residence time, agitation, sparging… but the gases are all special snowflakes with their own solubilities.
AFN: What stage are things at now?
SN: We’ve raised some money, got some grants, and built a pilot that’s pretty unusual in that it is an aerobic gas fermenter that is food grade, one of the only ones of its size in the world.
It can run in multiple different gas fermentation modes: loop [where gas and liquid circulate in a loop to enhance mixing], air lift [where gas bubbles lift the liquid upward], bubble column [where gas bubbles rise through a stationary liquid column], and agitated [where a mixer stirs the gas and liquid together].
As no one has scaled aerobic gas fermentation beyond a few 100 liters, we needed to know which technology to pick, so the pilot can run four of them.
AFN: What’s next after the pilot plant and how will you fund scaling up?
SN: We’ve done pretty well on getting non-dilutive funding, so the pilot plant was funded through an ARPA-E project [from the Department of Energy] and we think there are emerging opportunities in federal funding that will continue to help companies like ours scale.
So far we’ve raised $16 million from dilutive and non-dilutive funding combined and we’re currently raising a Series A round, but you have to demonstrate that the economics make sense if you want to be venture backable.
Our next step is to build a demo-scale plant with a 150 ton capacity, so we’re looking for offtake partners to justify the construction of that plant.
AFN: What kind of interest have you seen from the market in fats produced by your platform?
SN: It doesn’t make economic sense to try and compete with crude palm oil, but we’re seeing a lot of interest in being able to make palm oil fractions and dairy fats.
AFN: What keeps you awake at night?
SN: I’m not concerned about whether the tech will work. My concern is can we live long enough to demonstrate it works at scale, so we need to find financial partners that believe in the mission and believe in the potential. For foodtech investors, we’re more like chemical manufacturing, whereas for climate tech investors, we’re more bio, so we have to educate them both.
AFN: What’s the regulatory status of the fats and how might they be labeled?
SN: We’re just starting this journey, but our understanding from working with consultants is that we will have to demonstrate that the triglycerides the organisms are making are ones that are already found in food, and then show that our process doesn’t introduce additional changes to the product.
Labeling is to be determined but it will probably be something like cultured oil.
AFN: Are traces of the genetically engineered host organism in the final products/fats?
SN: No, so we can avoid a bioengineered label [in the US].
Further reading:
Can gas fermentation deliver on its green promise for food and feed? In conversation with Calysta
