Diversifying product portfolio of syngas fermentation in addition to ethanol production by using Clostridium species

Abstract

This study explores the impact of syngas, a mixture of CO (carbon monoxide), CO₂ (carbon dioxide) and H₂ (hydrogen), composition on production of ethanol and other metabolites by using various Clostridia. Clostridium carboxidivorans, Clostridium ljungdahlii, and Clostridium ragsdalei were examined to convert CO-rich syngas into ethanol and other valuable products, and C. carboxidivorans was shown to produce maximum ethanol at a high initial CO concentration (80 % CO: 10 % CO₂: 10 % H₂). In addition, other C2-C6 compounds, viz. lactate, propionate, butyrate, 2,3-butanediol, butanol, isovalerate, hexanol, were produced by C. carboxidivorans, C. ljungdahlii, and C. ragsdalei, indicating diversified product formation through the Wood-Ljungdahl pathway. Modified Gompertz and Logistic models were successfully applied to describe the kinetics of cell growth and ethanol production by Clostridia via syngas fermentation. The findings emphasize optimization of syngas composition for maximum production of ethanol and other valuable biochemicals, providing a sustainable approach to biofuels and bioproduct production.