The study was conducted to evaluate fermentation by Clostridium thermocellum and C. saccharoperbutylacetonicum in a continuous-flow, high-solids reactor. Liquid medium was continuously flowed through switchgrass (2 mm particle size) at one of three flow rates: 83.33 mL h1 (2 L d−1), 41.66 mL h−1 (1 L d−1), and 20.833 mL h−1 (0.5 L d−1). The cellulolytic phase was initiated by culturing C. thermocellum (63 °C, 24 h). The temperature was decreased (35) and C. saccharoperbutylacetonicum was inoculated. When metabolism decreased (96 h), the temperature was increased (63 °C; 24 h) to permit cellulosome production by C. thermocellum. The C. saccharoperbutylacetonicum was re-inoculated and the temperature returned to 35°C. The average gross production over 9 d was 1480 mg total acids (formic, acetic lactic butyric), 207 mg total solvents (acetone, butanol, ethanol), and average dry matter disappearance was 2.8 g from 25 g non-pretreated switchgrass. There was no effect of flow rate on the product formation. These results indicate that C. thermocellum can survive and produce cellulases with C. saccharoperbutylacetonicumin a continuous-flow, high-solids reactor temperature with temperature cycling.

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Published in AIMS Energy, v. 4, no. 1, p. 95-103.

© 2016 Michael Flythe et al., licensee AIMS Press.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0).

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United States Department of Agriculture National Institute for Food and Agriculture Biomass Research and Development Initiative (Grant number #2011-10006-30363) funded the research.