Bioconversion of C1-gases by mixotrophic co-cultures fermentation with C. carboxidivorans and C. beijerinkii.

The development of newfangled bioprocess strategies for the capture of C1-gases (CO and CO2) and their bioconversion into valuable products is currently one of the main focuses of research in order to achieve a more resilient world. This work analyses the viability of the co-culture C. carboxidivorans and C. beijerinkii to produce bioproducts (bioalcohols and organic acids) in mixotrophic conditions. In this way, the bioconversion of C1 gases (CO and CO2), in the presence of Fe0, using mixotrophic co-culture fermentation by C. carboxidivorans and C. beijerinkii, was evaluated, analyzing the influence of the ratio between both microorganisms, the pH, and the presence of Fe0. As a result, up to 7 g/L of butanol were achieved at pH 7, 12.5 g/L Fe0, and using a 1:1 ratio of C. carboxidivorans: C. beijerinkii, also improving the production of ethanol, acetic acid, and butyric acid as compared to individual culture fermentations. Finally, the operation in a bioreactor, comparing discontinuous and continuous gas feeding operation modes, was also studied, with better C1-gases utilization and overall fermentation efficiency (7 vs 4.6 g/L butanol) in continuous gas operation mode.