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

Abstract

C. saccharolyticum ferments glucose, cellobiose and xylose to CO2, H2, ethanol, acetate and lactate. The addition of 0.12 M CaCO3 and 1% yeast extract (wt/vol) to the glucose medium shifted the ethanol-acetate mol ratio from 1.35 to 2.6. Although the addition of exogenous H2 (240 kPa [kiloPascals] did not affect the growth of C. saccharolyticum, it did alter the pattern of fermentation products; H2 and acetate formation decreased, while ethanol production increased. Ethanol production also increased at the expense of H2 and acetate when C. saccharolyticum was incubated without shaking. Stationary incubation under a H2 headspace (standard temperature and pressure) resulted in an ethanol concentration, at 25.degree. C, of 1.7% (vol/vol), an efficiency of conversion of 1.8 mol ethanol/mol glucose and ethanol-acetate ratios of 7.6 at 35.degree. C and 9.4 at 20.degree. C. H2 apparently plays a significant role in the regulation of C. saccharolyticum catabolism.