Enhancement of bioethanol production in syngas fermentation with Clostridium ljungdahlii using nanoparticles

In this study, nanoparticles were used to enhance bioethanol production in syngas fermentation by Clostridium ljungdahlii. Six types of nanoparticles were tested: palladium on carbon, palladium on alumina, silica, hydroxyl-functionalized single-walled carbon nanotubes, alumina, and iron(III) oxide. Of these, silica nanoparticles at a concentration of 0.3 wt% were the best at enhancing gas–liquid mass transfer. The hydrophilic surfaces of silica nanoparticles were modified with hydrophobic functional groups such as methyl and isopropyl. Methyl-functionalized silica nanoparticles were better than unmodified and isopropyl-functionalized silica nanoparticles at enhancing mass transfer. The dissolved concentrations of CO, CO2, and H2 were enhanced by 272.9%, 200.2%, and 156.1%, respectively, by using methyl-functionalized silica nanoparticles. The use of methyl-functionalized silica nanoparticles at a concentration of 0.3 wt% during syngas fermentation by C. ljungdahlii led to significant increases in the levels of biomass, ethanol, and acetic acid production (34.5%, 166.1%, and 29.1%, respectively).