Fig. 2.

Central carbon metabolism and relevant metabolic pathways of P. freudenreichii subsp. shermanii discussed in this work. Pathways are colour-coded. Upregulation of the glycine cleavage pathway, TCA cycle (via the alpha-ketoglutarate dehydrogenase), the citramalate pathway or the PPP are all possible ways to source additional reduced cofactors for propionate generation, although the ATP generation through the glycine cleavage pathway makes this particularly attractive. Potential knock-out strategies target glycolysis or the acetate synthesis pathway. Non-native enzymes proposed in this work are depicted in black.