PRODUCTION OF ETHANOL BY ZYMOMONAS-MOBILIS - THE EFFECT OF BATCH STEP-FEEDING OF GLUCOSE AND RELEVANT GROWTH-FACTORS

Ethanol production by Zymomonas mobilis (ATCC 10988) was studied by us ing different concentrations offglucose (50-300 g/litre). A glucose co ncentration of 50-150 g/litre showed the highest ethanol-yield efficie ncy. Step-feeding of glucose was attempted to increase ethanol product ion and to reduce substrate inhibition. A step-feeding system for a to tal glucose concentration of 200 g/litre was found suitable. The speci fic growth rate was reduced as the number of steps increased. The effe ct of inoculum age, yeast extract, and peptone on the step-feeding sys tem was studied. A suitable combination of yeast extract and peptone w as selected on the basis of the central-composite-rotatable-design (CC RD) procedure.