Conversion of starch into ethanol by Clostridium thermohydrosulfuricum

Summary Production of ethanol from starch by Clostridium thermohydrosulfuricum was compared with that from glucose, fructose or maltose in batch fermentations. Optimal substrate concentration and pH for ethanol production were determined. The rate of ethanol production on starch was about the same as that on glucose or fructose and overall yields were also similar (about 1.6 mol ethanol per mol glucose or glucose equivalent). Maltose was not an effective substrate for growth and ethanol production.When a mixture of starch and glucose in equal amounts was used, breakdown of starch and utilization of glucose were simultaneous. When starch and fructose were supplied together, the fructose was utilized but no hydrolysis of starch was observed. With a mixture of glucose and fructose, uptake of fructose preceeded that of glucose.