Cauldron Firm has turned microbes into non-stop assembly lines

Cauldron Ferm has an unexpected origin story, as startups do. Its basic technology can be traced back to the 1960s, or perhaps the 1970s. The exact beginning is a bit hazy, actually. David and Polly McLennan dreamed of feeding the world using protein grown from microbes.

The duo realized they needed to improve the process, which was expensive and time-consuming. Most fermentation occurs in batches. Visualize a brewery or vineyard. The ingredients go in and the microbes work for a while, but then the process stops when it’s time to take out the final product. It is suitable for alcohol because wine commands a high price. Food, however? It should be cheaper.

However, the McLennans stuck with it, starting a small business that would over the course of 40 years improve their method of continuous fermentation, which turns microbes into assembly lines capable of producing products without interruption.

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

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

Cauldron has now raised $13.25 million in a Series A2 round 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 its technology moat,” Stansfield said.

The company calls its technology “hyperfermentation,” which helps keep microbes in their peak productive state. It can work in existing batch fermenters with some modifications to the facility to accommodate the process. Cauldron’s customers bring their own microbes and strains, and the startup tweaks their growth conditions, including nutrients, to keep them active.

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

“60% of all inputs to the global economy can be produced from biology,” she said. “Food was where we started, but now we’re starting to really diversify.”