Examining mixotrophic fermentation in fed‐batch mode for <scp>C1</scp>‐gas valorization

Abstract BACKGROUND C1‐gases like CO and CO 2 , significant contributors to climate change, offer the potential for sustainable bioconversion into valuable products. The study explored mixotrophic fermentation using C1‐gases in fed‐batch mode to improve the production of target compounds, focusing on Clostridium aceticum and Clostridium carboxidivorans . It aimed to overcome the limitations of conventional gas fermentation (autotrophic fermentation and without fed‐batch mode) and assess the potential of mixotrophic substrates for enhancing yields. RESULTS Results showed that mixotrophic fermentation with fructose as a co‐substrate led to higher microbial growth in C. aceticum , increasing acetic acid (1200 versus 600 mg L −1 ) and ethanol (600 versus 0 mg L −1 ) production, compared to autotrophic fermentation. For C. carboxidivorans , constant CO consumption occurred in autotrophic and mixotrophic fermentation. Mixotrophic fermentation with fructose and C1‐gases by C . carboxidivorans significantly boosted microbial growth and metabolic activity, increasing butanol (1600 versus 0 mg L −1 ) and butyric acid (2400 versus 1800 mg L −1 ) production, compared to autotrophic fermentation. CONCLUSIONS The study highlights mixotrophic fermentation's potential to enhance C1‐gas valorization. It provides insights into microbial behavior under varied substrate conditions, contributing to sustainable biomanufacturing practices for biofuel and high‐value bioproducts. © 2025 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry (SCI).