EngineeringSaccharomyces cerevisiaefor Succinic Acid Production From Glycerol and Carbon Dioxide

Previously, our lab replaced the endogenous FAD-dependent pathway for glycerol catabolism inS. cerevisiaeby the synthetic NAD-dependent dihydroxyacetone (DHA) pathway. The respective modifications allow the full exploitation of glycerol's higher reducing power (compared to sugars) for the production of the platform chemical succinic acid (SA) via a reductive, carbon dioxide fixing and redox-neutral pathway in a production host robust for organic acid production. Expression cassettes for three enzymes converting oxaloacetate to SA in the cytosol (SA module) were integrated into the genome ofUBR2(CBS)-DHA, an optimized CEN.PK derivative. Together with the additional expression of the heterologous dicarboxylic acid transporter DCT-02 fromAspergillus niger, a maximum SA titer of 10.7 g/L and a yield of 0.22 +/- 0.01 g/g glycerol was achieved in shake flask (batch) cultures. Characterization of the constructed strain under controlled conditions in a bioreactor supplying additional carbon dioxide revealed that the carbon balance was closed to 96%. Interestingly, the results of the current study indicate that the artificial SA module and endogenous pathways contribute to the SA production in a highly synergistic manner.