Fermentation of glucose by Zymomonas mobilis CP4 utilising continuous transient technique

Abstract

Ethanol production by Zymomonas mobilis CP4 under continuous transient operation has been investigated. The bacteria was grown under alternating glucose amplitudes of 2% and 5% (w/p) and cycle time values of 2, 4 and 6 hours. The ethanol production was compared to data obtained in simple chemostat operation grown 3.5%(w/v) glucose medium. The value of dilution rate was fixed as 0.2h-1 for both techniques. When cycle time value of 2 hours was used, values of biomass and ethanol kept constant. The appliance of cycle time of 4 hours produced smooth responses from the organisms. The values of biomass oscillated from 0.7 to 0.93 g/l. When cycle time of 6 hours was used the oscillations on biomass and ethanol were pronounced. The minimum and maximum values of biomass were respectively 0.61 and 1g/l. As far as conversion efficiency to ethanol is concerned the values of 84, 85 and 89% (corresponding to cycle time of 2, 4 and 6 hours) were found whereas conversion efficiency was low as 50% when simple chemostat was used.

Keywords

• Continuous transient operation
• Continuous culture
• Zymomonas mobilis