Cauldron Farm turned microbes into continuous assembly lines

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

The couple knew they needed to improve the expensive and time-consuming process. Most fermentation takes place in groups. Imagine a brewery or a vineyard. The ingredients go in and the microbes work for a while, but then when it’s time to remove the finished product, the process stops. It works for alcohol because liquor commands a high price. Food, though? It should be cheaper.

However, the McLennans stuck with it and started a small business that would spend 40 years perfecting their approach to continuous fermentation, which transforms microbes into assembly lines that can continuously churn out product.

“We had no idea what we had,” Michelle Stansfield, co-founder and CEO Boiler Farmtold TechCrunch. But Stansfield, who eventually joined the McLennans’ company in 2012, realized they had more than they first thought.

“We didn’t understand the challenge of sustainable fermentation for synthetic biology,” Stansfield said. But when he did, he tried to transform the company from a small paid service operator to a fast-moving startup. “At that point, I collected a number of and acquired IP, physical and business assets.”

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

The company calls this technology “hyper-fermentation,” which helps keep microbes at peak productivity. It can work in existing batch fermenters with few modifications to the facility to accommodate the process. Cauldron’s customers bring their own microbes and strains, and the startup tries to adjust their growth conditions, including nutrients, to keep them humming.

Right now, Cauldron is focused on making fats and proteins, including whey proteins, “a product that can just go into supply chains,” Stansfield said, although the company has more products it’s focused on.

“Sixty percent of all inputs to the global economy can be derived from biology,” he said. “Where we started was food, but now we’re really starting to diversify.”