# Circe

> Circe (Circe Bioscience) is a Boston-based climate biotech company that engineers microbes to eat carbon dioxide and build valuable molecules - fats, oils, sugars, plastics and fuels - using only CO2, water and electricity. Spun out of Harvard's Wyss Institute in 2021, its gas-fermentation platform consumes roughly 3 kilograms of CO2 for every kilogram of oil it produces, making the process carbon-negative. The company has made the world's first chocolate using fermentation-derived cocoa butter and, in September 2024, raised a $5M seed round to open a pilot plant in Waltham, Massachusetts.

- **Founded:** 2021
- **Headquarters:** Boston, Massachusetts, United States
- **Founders:** Shannon Nangle (Co-founder & CEO), Marika Ziesack (Co-founder)
- **Team size:** Approximately 25-50 (public listings cite ~51)
- **Products:** Gas fermentation platform, Carbon-negative fats and oils, Fermentation-derived cocoa butter, Molecule platform (industry-agnostic)
- **Notable:** Made what it calls the world's first chocolate using fermentation-derived cocoa butter, Spun out of Harvard's Wyss Institute in 2021 with a worldwide exclusive technology license, Opened a pilot plant in Waltham, MA - described as the world's most advanced aerobic gas fermentation facility

## Products & services

- **Gas fermentation platform** — An engineered-microbe process that converts CO2 (and related gases), water and electricity into complex molecules, growing the way plants do but tuned to produce specific target compounds.
- **Carbon-negative fats and oils** — Triglycerides and specialty fats for food, cosmetics and biofuels, produced with roughly 3 kg of CO2 consumed per kg of oil.
- **Fermentation-derived cocoa butter** — A cocoa butter that is molecularly identical to the tree-grown version, used to make what Circe calls the world's first gas-fermentation-based chocolate.
- **Molecule platform (industry-agnostic)** — Demonstrated prototypes spanning confectionery, dairy ingredients, sugars, proteins, biodegradable polymers and biofuels from the same core process.

## Achievements

- Made what it calls the world's first chocolate using fermentation-derived cocoa butter
- Spun out of Harvard's Wyss Institute in 2021 with a worldwide exclusive technology license
- Opened a pilot plant in Waltham, MA - described as the world's most advanced aerobic gas fermentation facility
- Awarded a US Department of Energy ARPA-E ECOSynBio contract (~$3.2M)
- Founders named 2021 Activate Fellows and Wyss Lumineers
- CEO Shannon Nangle named an MIT Technology Review 'Innovator Under 35'

## Latest updates

- **2024-09** — Announced a $5M seed round and the installation of its pilot plant in Waltham, MA, moving carbon-negative molecule production out of the lab.
- **2024-05** — Signed a worldwide exclusive license with Harvard's Wyss Institute to commercialize the gas-fermentation technology.
- **2024-05** — Publicized its fermentation-derived cocoa butter, used to make a chocolate bar 'out of thin air.'

## Links

- Website: https://circebioscience.com
- LinkedIn: https://www.linkedin.com/company/circe-bio

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Profile page: https://yespress.io/circe
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Last updated: 2026-07-06