Ethanol production by Zymomonas mobilis in fed-batch fermentations.
The production of ethanol by Zymomonas mobilis NRRL B-4286 was studied in fed-batch cultures. Initial percent (w/v) glucose, rate of feed, and quantity of 50%; (w/v) glucose feed were varied. Glucose inhibition of growth rate occurred at concentrations greater than 8% (w/) Feed was begun after 4 h incubation. Feed volume was ca. 36%; of starting batch volume to get ca. 10%; (w/v) ethanol at harvest. The range of feed rates studied varied from 16%; batch volume/h (glucose concentration increased to an inhibitory level) to 4%; batch volume/h (glucose concentration dropped rapidly to zero and was limiting). Increasing feed volume to 46%; of starting volume at the best feed rate (ca. 10%; feed volume/h) increased final ethanol concentration to 11.3%; (w/v). However, the resultant increase in fermentation time from ca. 21 to 29 h decreased ethanol volumetric productivity from 5.2 to 4.6 g/L h.
Northern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Peoria, Illinois 61604The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.
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Silman