Feasibility of incorporating cotton seed extract in Clostridium strain P11 fermentation medium during synthesis gas fermentation

Biomass gasification followed by fermentation of syngas to ethanol is a potential process to produce bioenergy. To make this process more economical, the complexity of media should be reduced while using less costly components. In this study, the feasibility of incorporating cotton seed extract (CSE) as a media component for syngas fermentation to produce ethanol using Clostridium strain P11 was evaluated. A factorial experiment was conducted to screen and evaluate the effect of different media components, in relation to CSE, on ethanol production. Also, different CSE concentrations as well as the presence of MES buffer were tested to determine their effect on ethanol production. Bottle fermentations with media containing only 1.0 g L−1 CSE produced more ethanol after 15 d (1.17 g L−1) than fermentation using any other media. Further bottle experiments showed that media containing only 0.5 g L−1 CSE produced more ethanol after 15 days (2.67 g L−1) than a control media (0.6 g L−1) and media containing only 1.0 g L−1 CSE (2.16 g L−1). Fermentations in 5- and 7.5-L stirred fermentors with 0.5 g L−1 CSE media achieved ethanol concentrations similar to those observed in bottle studies. These results indicate that CSE can replace all the vitamin and mineral media components generally used for fermentation of syngas to ethanol by Clostridium strain P11, thereby improving the process economics.