Harnessing the potential of Cupriavidus necator for CO2 capture from alcoholic fermentation and its bioconversion into poly(3-hydroxybutyrate).

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.