KINETICS OF ETHANOL-PRODUCTION BY RECOMBINANT ESCHERICHIA-COLI KO11

The fermentation kinetics for separate as well as simultaneous glucose and xylose fermentation with recombinant ethanologenic Escherichia co li KO11 are presented. Glucose and xylose were consumed simultaneously and exhibited mutual inhibition. The glucose exhibited 15 times stron ger inhibition in xylose fermentation than vice versa. The fermentatio n of condensate from steam-pretreated willow (Salix) was investigated. The kinetics were studied in detoxified as well as in nondetoxified c ondensate. The fermentation of the condensate followed two phases: Fir st the glucose and some of the pentoses (xylose in addition to small a mounts of arabinose) were fermented simultaneously, and then the remai ning part of the pentoses were fermented. The rate of the first phase was independent of the detoxification method used, whereas the rate of the second phase was found to be strongly dependent. When the condens ate was detoxified with overliming in combination with sulfite, which was the best detoxification method investigated, the sugars in the con densate, 9 g/L, were fermented in 11 h. The same fermentation took 150 h in nondetoxified condensate, The experimental data were used to dev elop an empirical model, describing the batch fermentation of recombin ant E. coli KO11 in the condensate. The model is based on Monod kineti cs including substrate and product inhibition and the sum of the inhib ition exerted by the rest of the inhibitors, lumped together. (C) 1995 John Wiley and Sons, Inc.