Engineering Saccharomyces cerevisiae for Succinic Acid Production From Glycerol and Carbon Dioxide
Joeline Xiberras, Mathias Klein, Erik de Hulster, Robert Mans, Elke Nevoigt
Abstract
Previously, our lab replaced the endogenous FAD-dependent pathway for glycerol catabolism in S. cerevisiae by 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 of UBR2CBS-DHA, an optimized CEN.PK derivative. Together with the additional expression of the heterologous dicarboxylic acid transporter DCT-02 from Aspergillus niger, a maximum SA titre 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.