KINETICS OF CONTINUOUS ETHANOL-PRODUCTION BY ZYMOMONAS-MOBILIS ON SUGAR-CANE MOLASSES

Kinetics parameters on sugar cane molasses were analyzed under differe nt experimental conditions using Zymomonas mobilis CP4 in continuous c ulture. The effect of the dilution rate at molasses medium concentrati on of 100 and 135 g/L, molasses concentration at dilution rate of 0.17 h-1 and fermentation temperature at dilution rate of 0.17 h-1 were st udied. At a dilution rate of 0.28 h-1 the ethanol productivity, yield and concentration respectively were 8.3 g/L.h, 0.42 g/g and 30 g/L wit h 100 g/L molasses medium concentration. At molasses medium concentrat ion of 135 g/L, at a dilution rate of 0.23 h-1, the ethanol concentrat ion reached 33 g/L giving 85% sugar conversion and ethanol productivit y of 7.4 g/L.h. In both cases the ethanol yield was over 80% of the th eoretical value. The maintenance energy coefficient (m) was relatively high and was calculated as 2.89 and 5.59 g/g.h for 100 and 135 g/L mo lasses medium concentration respectively. The kinetics parameters: wer e affected negatively only when the molasses medium concentration was upper than 135 g/L. Under our conditions, the fermentation could be ru n from 30 to 35 degrees C without any change in kinetics and yield par ameters.