RATE AND YIELD LIMITING FACTORS IN CONTINUOUS FERMENTATION OF SUCROSE BY ZYMOMONAS-MOBILIS

The initial transfer of fructosyl units in the utilization of sucrose led to the formation of fructose, oligomers or levan and was apparently controlled by the concentrations of sugars in the medium. In continuous fermentation, the rather low levels of monomeric sugars in the broth prevented the formation of sorbitol and oligomers, whereas the production of levan was increased compared to that in batch fermentation. The fructooligomers contained approximately one mole of glucose per two, three or four moles of fructose. The overall ethanol production rate was limited by the uptake rates of glucose and especially of fructose, which was decreased due to transfructosylation reactions.