Sustainable biomanufacturing requires moving beyond fossil and agricultural carbon sources. To date, industrial biotechnology depends largely on starch, sugar, and plant-derived glycerol, creating competition with food and feed production and pressure on limited arable land. Yet, microbial metabolism is not inherently constrained to these substrates, opening opportunities for alternative feedstocks. Non-agricultural carbon sources, particularly single- and two-carbon (C1 and C2) compounds, offer a compelling alternative. Produced from CO 2 via electrochemical or biological routes, methanol, formate, acetate, and ethanol connect renewable energy with microbial synthesis while enabling carbon recycling. Their use, however, introduces distinct metabolic and thermodynamic constraints, including limitations in energy conservation, redox balance, and pathway driving forces. Here, we examine C1 and C2 assimilation pathways in yeasts, highlighting key bottlenecks and engineering advances that make sustainable circular biomanufacturing possible. • CO 2 -derived feedstocks drive circular, sustainable biomanufacturing. • Engineered yeasts can metabolize C1 and C2 substrates. • Thermodynamic analysis reveals key features of C1 and C2 pathways.
Bachleitner et al. (Thu,) studied this question.