Substrate type and CO₂ addition significantly influence succinic acid production of Basfia succiniciproducens

Metabolic engineering has shown that optimizing metabolic pathways' fluxes for industrial purposes requires a methodical approach. Accordingly, in this study, in silico metabolic modeling was utilized to characterize the lesser-known strain Basfia succiniciproducens under different environmental conditions, followed by the use of industrially relevant substrates for succinic acid synthesis. Based on RT-qPCR carried out in flask experiments, we discovered a relatively large difference in the expression levels of ldhA gene compared to glucose in both xylose and glycerol cultures. In bioreactor-scale fermentations, the impact of different gas phases (CO₂, CO₂/AIR) on biomass yield, substrate consumption, and metabolite profiles was also investigated. In the case of glycerol, the addition of CO₂ increased biomass as well as target product formation, while using CO₂/AIR gas phase resulted in higher target product yield (0.184 mM⋅mM^-1). In case of xylose, using CO₂ alone would result in higher succinic acid production (0.277 mM⋅mM^-1). The promising rumen bacteria, B. succiniciproducens, has shown to be suitable for succinic acid production from both xylose and glycerol. As a result, our findings present new opportunities for broadening the range of raw materials used in this significant biochemical process. Our study also sheds light on fermentation parameter optimization for this strain, namely that, CO₂/AIR supply has a positive effect on target product formation.