ETHANOL-PRODUCTION FROM AFEX PRETREATED CORN FIBER BY RECOMBINANT BACTERIA

Fermentation of an enzymatic hydrolyzate of ammonia fiber explosion (A FEX) pretreated corn fiber (containing a mixture of different sugars i ncluding glucose, xylose, arabinose, and galactose) by genetically-eng ineered Escherichia coli strain SL40 and KO11 and Klebsiella oxytoca s train P2 was investigated under pH-controlled conditions. Both E. coli strains (SL40 and KO11) efficiently utilized most of the sugars conta ined in the hydrolyzate and produced a maximum of 26.6 and 27.1 g/l et hanol, respectively, equivalent to 90 and 92% of the theoretical yield . Very little difference was observed in cell growth and ethanol produ ction between fermentations of the enzymatic hydrolyzate and mixtures of pure sugars, simulating the hydrolyzate. These results confirm the fermentability of the AFEX-treated corn fiber hydrolyzate by ethanolog enic E. coli. K. oxytoca strain P2, on the other hand, showed comparat ively poor growth and ethanol production (maximum 20 g/l) from both en zymatic hydrolyzate and simulated sugar mixtures under the same fermen tation conditions.