Harnessing the potential of Cupriavidus necator for CO₂ capture from alcoholic fermentation and its bioconversion...

The fermentation process in alcoholic beverage production converts sugars into ethanol and CO₂, releasing significant amounts of greenhouse gases. Here, Cupriavidus necator DSM 545 was grown autotrophically using gas derived from alcoholic fermentation, using a fed-batch bottle system. Nutrient starvation was applied to induce intracellular accumulation of poly(3-hydroxybutyrate) (PHB), a bioplastic polymer, for bioconversion of CO₂-rich waste gas into PHB. Grape marc, another by-product of wine production, was evaluated as a low-cost carbon source for the heterotrophic growth of C. necator, which was subsequently used as an inoculum for autotrophic cultures. The effect of agitation, CO₂ headspace composition, and nitrogen concentration was tested, obtaining a maximum PHB concentration of 0.69 g/L, with an average CO₂ uptake rate of 1.14 ± 0.41 mmol CO₂ L^-1h^-1 and 65 % efficiency of CO₂ consumption. These findings lay the groundwork for developing carbon mitigation strategies in alcoholic fermentation processes coupled with sustainable biopolymer production.