Continuous ethanol production by thermotolerant Kluyveromyces marxianus IMB3 immobilized on mineral Kissiris at 45°C

Thermotolerant Kluyveromyces marxianus var. marxianus IMB3 yeast strain was immobilized on Kissiris (mineral glass foam derived from lava) in column packed reactors, and used for ethanol production from glucose or molasses under continuous culture conditions at temperatures between 40 and 50°C. Both ethanol yield and fermentation efficiency were highest at 45°C and a dilution rate (D) of 0.15/h. Increasing sugar concentration led to an increase in ethanol yield of up to 68.6 and 55.9 g/l on approx. 200g glucose or molasses, respectively. Optimum fermentation efficiency (experimental yields over theoretical maximum yields) however was at about 15% sugar for both glucose and molasses. Slight aeration (25 ml of air/min) through the medium addition line was found advantageous due to its mixing effect and probable maintenance of activity.