Power-to-vitamins: producing folate (vitamin B9) from renewable electric power and CO2 with a microbial protein system.

We recently proposed a two-stage Power-to-Protein technology to produce microbial protein from renewable electric power and CO₂. Two stages were operated in series: Clostridium ljungdahlii in Stage A to reduce CO₂ with H₂ into acetate, and Saccharomyces cerevisiae in Stage B to utilize O₂ and produce microbial protein from acetate. Renewable energy can be used to power water electrolysis to produce H₂ and O₂. A drawback of Stage A was the need for continuous vitamin supplementation. In this study, by using the more robust thermophilic acetogen Thermoanaerobacter kivui instead of C. ljungdahlii, vitamin supplementation was no longer needed. Additionally, S. cerevisiae produced folate when grown with acetate as a sole carbon source, achieving a total folate concentration of 6.7 mg per 100 g biomass with an average biomass concentration of 3 g l^-1. The developed Power-to-Vitamin system enables folate production from renewable power and CO₂ with zero or negative net-carbon emissions.