Cauldron Ferm has turned microbes into nonstop assembly lines

Cauldron Ferm has an unlikely origin story, as startups go. Its core technology can be traced back to the 1960s, or maybe the 1970s. The exact start is a bit hazy, actually. What is known is that David and Polly McLennan had a dream of feeding the world using protein grown from microbes.

The pair knew they needed to improve the process, which was pricy and time consuming. Most fermentation happens in batches. Picture a brewery or a vineyard. Ingredients go in and the microbes work for a while, but then the process stops when it’s time to take out the finished product. It works for alcohol because booze commands a premium price. Food, though? That needs to be cheaper.

Still, the McLennans stuck with it, starting a small business that would over the course of 40 years refine their approach to continuous fermentation, which turns microbes into assembly lines capable of cranking out products uninterrupted.

“We didn’t know what we had,” Michele Stansfied, co-founder and CEO of Cauldron Ferm, told TechCrunch. But eventually, Stansfield who arrived at the McLennans’ company in 2012, realized they had more than initially thought.

“We didn’t understand the challenge of continuous fermentation for synthetic biology,” Stansfield said. But when she did, she sought to transform the company from a small fee-for-service operators to a fast-moving startup. “At that point, I raised a seed round and acquired the IP, physical, and business assets.”

Cauldron has now raised $13.25 million in a Series A2 round that was led by Main Sequence Ventures with participation from Horizons Ventures, NGS Super, and SOSV, the company exclusively told TechCrunch. It had previously raised $6.5 million in 2024. Cauldron plans to use the funding to “increase the technology moat,” Stansfield said. 

The company calls it’s technology “hyper fermentation,” which helps keep microbes in their maximally productive state. It can work in existing batch fermenters with a few modifications to the facility to accommodate the process. Cauldron’s customers bring their own microbes and strains, and the startup works to tweak their growing conditions, including nutrients, to keep them humming.

Currently, Cauldron is focused on producing fats and proteins, including whey protein, “a product that can just slip into supply chains,” Stansfield said, though she adds there are more products the company has its eyes on.

“Sixty percent of all inputs to global economy can be produced from biology,” she said. “Food was where we started, but now we’re starting to really diversify.”