Characterization of recombinantE. coli ATCC 11303 (pLOI 297) in the conversion of cellulose and xylose to ethanol

This work describes the characterization of recombinantEsherichia coli ATCC 11303 (pLOI 297) in the production of ethanol from cellulose and xylose. We have examined the fermentation of glucose and xylose, both individually and in mixtures, and the selectivity of ethanol production under various conditions of operation. Xylose metabolism was strongly inhibited by the presence of glucose. Ethanol was a strong inhibitor of both glucose and xylose fermentations; the maximum ethanol levels achieved at 37°C and 42°C were about 50 g/l and 25 g/l respectively. Simmultaneous sacharification and fermentation of cellulose with recombinantE. coli and exogenous cellulose showed a high ethanol yield (84% of theoretical) in the hydrolysis regime of pH 5.0 and 37°C. The selectivity of organic acid formation relative to that of ethanol increased at extreme levels of initial glucose concentration; production of succinic and acetic acids increased at low levels of glucose ( <1 g/l), and lactic acid production increased when initial glucose was higher than 100 g/l.