Synergistic Substrate Cofeeding Stimulates Reductive Metabolism

Abstract

Advanced bioproduct synthesis via reductive metabolism requires coordinating carbons, ATP, and reducing agents, which are generated with varying efficiencies depending on metabolic pathways. Substrate mixtures with direct access to multiple pathways may optimally satisfy these biosynthetic requirements. However, native regulation favoring preferential utilization precludes cells from co-metabolizing multiple substrates. Here we explore mixed substrate metabolism and tailor pathway usage to synergistically stimulate carbon reduction. By controlled cofeeding of superior ATP- and NADPH-generators as “dopant” substrates to cells primarily utilizing inferior substrates, we circumvent catabolite repression and drive synergy in two divergent organisms. Glucose doping in Moorella thermoacetica stimulates CO2 reduction (2.3 g gcell–1 hr–1) into acetate by augmenting ATP synthesis via pyruvate kinase. Gluconate doping in Yarrowia lipolytica accelerates acetate-driven lipogenesis (0.046 g gcell–1 hr–1) by obligatory NADPH synthesis through the pentose cycle. Together, synergistic cofeeding produces CO2-derived lipids with 38% energy yield and demonstrates potential to convert CO2 into advanced bioproducts. This work advances the systems-level control of metabolic networks and CO2 utilization, the most pressing and difficult reduction challenge.