Ethanol production by a newly isolated anaerobe, <i>Clostridium saccharolyticum</i>: effects of culture medium and growth conditions

Abstract

Clostridium saccharolyticum was shown to ferment glucose, cellobiose, and xylose to CO 2 , H 2 , ethanol, acetate, and lactate. The addition of 0.12 M CaCO 3 and 1% yeast extract (w/v) to the glucose medium was found to shift the ethanol–acetate mole ratio from 1.36 to 2.6. Although the addition of exogenous H 2 (240 kPa) did not affect the growth of C. saccharolyticum, it did alter the pattern of fermentation products. Both H 2 and acetate formation decreased, while ethanol production increased. Ethanol production also increased at the expense of H 2 and acetate when C. saccharolyticum was incubated without shaking. Stationary incubation under a H 2 headspace (standard temperature and pressure) resulted in an ethanol concentration, at 25 °C, of 1.7% (v/v), an efficiency of conversion of 1.8 mol ethanol/mol glucose, and ethanol–acetate ratios of 7.6 at 35 °C and 9.4 at 20 °C. These results indicate that H 2 concentration plays a significant role in the regulation of C. saccharolyticum catabolism.