EFFECTS OF PROCESS ERRORS ON THE PRODUCTION OF ETHANOL BY ESCHERICHIA-COLI KO11

Escherichia coli KO11 was previously constructed for the production of ethanol from both hexose and pentose sugars in hemicellulose hydrolys ates by inserting the Zymomonas mobilis genes encoding pyruvate decarb oxylase (pdc) and alcohol dehydrogenase (adhB). This biocatalyst appea rs relatively resistant to potential process errors during fermentatio n. Antibiotics were not required to maintain the maximum catabolic act ivity of KO11 even after deliberate contamination with up to 10% soil, Fermentations exposed to extremes of temperature (2 h at 5 degrees C or 50 degrees C) or pH (2 h at pH 3 or pH 10) recovered after re-adjus tment to optimal fermentation conditions (35 degrees C, pH6) although longer times were required for completion in most cases. Ethanol yield s were not altered by exposure to extremes in temperature but were red uced by exposure to extremes in pH, Re-inoculation with 5% (by volume) from control fermenters reduced this delay after exposure to pH extre mes.