The Use of Oxygen Uptake Rate to Optimise Air Feed Rate to a Continuous Ethanol Fermentation

Catherine Hack, R. Marchant and W. McClean

Department of Applied Biological and Chemical Science, University of Ulster at Coleraine, Co. Londonderry, Northern Ireland BT52 1SA

Article history:
Received November 25, 1994
Accepted December 22, 1994

Summary:
In a continuous ethanol fermentation in a stirred tank reactor, the effect of oxygen transfer rate on the biomass concentration, specific activity and overall ethanol productivity of a thermotolerant yeast Kluyveromyces marxianus was investigated. The dissolved oxygen concentration was maintained at zero. Although an increased oxygen transfer rate led to an increase in biomass concentration, the reduction in specific activity led to a reduction in overall cthanol productivity. The optimum oxygen transfer rate was zero. The maximum ethanol productivity was 1.3 mL/L h. The ethanol productivity in the stirred tank reactor was compared with two alternative fermenter configurations:
- two fermenters in series
- poorly mixed aerated fermenter
An ethanol productivity of 3.9 mL/L h was achieved in both these systems.