Systems-wide analysis and engineering of metabolic pathway fluxes in bio-succinate producing Basfia succiniciproducens

ABSTRACT Basfia succiniciproducens has been recently isolated as novel producer for succinate, an important platform chemical. In batch culture, the wild type exhibited a high natural yield of 0.75 mol succinate (mol glucose)−1. Systems‐wide 13C metabolic flux analysis identified undesired fluxes through pyruvate‐formate lyase (PflD) and lactate dehydrogenase (LdhA). The double deletion strain B. succiniciproducens ΔldhA ΔpflD revealed a 45% improved product yield of 1.08 mol mol−1. In addition, metabolic flux analysis unraveled the parallel in vivo activity of the oxidative and reductive branch of the TCA cycle in B. succiniciproducens, whereby the oxidative part mainly served for anabolism. The wild type re‐directed surplus NADH via a cycle involving malic enzyme or via transhydrogenase, respectively, to supply NADPH for anabolism, because the fluxes through the oxidative PPP and isocitrate dehydrogenase, that also provide this cofactor, were not sufficient. This was not observed for the deletion mutants, B. succiniciproducens ΔpflD and ΔldhA ΔpflD, where PPP and isocitrate dehydrogenase flux alone matched with the reduced anabolic NADPH demand. The integration of the production performance into the theoretical flux space, computed by elementary flux mode analysis, revealed that B. succiniciproducens ΔldhA ΔpflD reached 62% of the theoretical maximum yield. Biotechnol. Bioeng. 2013;110: 3013–3023. © 2013 Wiley Periodicals, Inc. Basfia succiniciproducens, a succinate producing rumen isolate, was investigated by 13C metabolic flux analysis. Systems‐wide pathway fluxes suggested pyruvate‐formate lyase and lactate dehydrogenase as the most promising targets towards strain improvement. Subsequent deletion of the encoding genes boosted succinate production by 45% up to a yield of 1.08 mol mol−1.