CO2-based production of C2-C6 acids and alcohols: The potential of novel Clostridia

Abstract

This study compared conversion of CO2 into C2-C6 products by Clostridium carboxidivorans P7 and P20, C. ragsdalei P11, C. ljungdahlii P14 and C. muellerianum P21. The effects of medium components and inoculum growth conditions on CO2 fermentation were evaluated. Fermentations were performed in 250-mL bottle assays at 125 rpm and 37 °C, using H2:CO2:N2 (60:20:20) that was fed daily for 360 h. Results showed that CO2 fermentations in corn steep liquor medium outperformed those in yeast extract-based media, with strain P11 producing 4.5 g/L ethanol and strain P21 producing 0.5 g/L hexanol. Alcohol formation was 2- to 4-fold higher using inocula pre-grown on syngas compared to H2:CO2. Strain P21 demonstrated higher C4 and C6 alcohols production compared to other strains. Further improvements are necessary to enhance activity and selectivity for converting CO2 into desired products.