Characterizing Novel Acetogens for Production of C2–C6 Alcohols from Syngas

Abstract

Utilizing syngas components CO, CO2, and H2 to produce fatty acids and alcohols offers a sustainable approach for biofuels and chemicals, reducing the global carbon footprint. The development of robust strains, especially for higher alcohol titers in C4 and C6 compounds, and the creation of cost-effective media are crucial. This study compared syngas fermentation capabilities of three novel strains (Clostridium carboxidivorans P20, C. ljungdahlii P14, and C. muellerianum P21) with existing strains (C. ragsdalei P11 and C. carboxidivorans P7) in three medium formulations. Fermentations in 250-mL bottles were conducted at 37 °C using H2:CO2:CO (30:30:40) using P11, P7, and corn steep liquor (CSL) media. Results showed that P11 and CSL media facilitated higher cell mass, alcohol titer, and gas conversion compared to the P7 medium. Strains P7, P14, and P20 formed 1.4- to 4-fold more total alcohols in the CSL medium in comparison with the P7 medium. Further, strain P21 produced more butanol (0.9 g/L) and hexanol (0.7 g/L) in the medium with CSL, offering cost advantages over P7 and P11 media containing yeast extract. Enhancing strain activity and selectivity in converting syngas into C4 and C6 alcohols requires further development, medium formulation improvements, and characterization, particularly for the new strain P21.