Effect of Alteration of the Acetic Acid Synthesis Pathway on the Fermentation Pattern of Escherichia coli

DÍAZ RICCI, JUAN C.; REGAN, L.; BAILEY, JAMES E.

BIOENGINEERING AND BIOTECHNOLOGY

JOHN WILEY & SONS INC

Lugar: New York; Año: 1991 vol. 38 p. 1318 - 1324

0006-3592

The glucose metabolism ofan Escherichiacoli strainbearingmutations abolishing bothacetyl phosphotransferase(PTA) and acetate kinase(ACK) activities was studied underaerobic and anaerobicconditions. These studies wereconducted in a complex medium with the mutantcarryingno plasmid, the mutantcarrying the common cloning vectorpUC19, and the mutantcarrying a plasmid bearing the?pet? operon that encodes Zymomonas mobilispyruvatedecarboxylase and alcoholdehydrogenase activities. Themutant carrying no plasmidshowed lower specific growthand glucose uptake ratesrelative to the parent wild-typestrain (K-12). Lactic acidwas produced at higher levels thanthe wild type, and considerableamounts of pyruvic acidwere secreted as anunusual byproduct. Analysis of otherfermentation productsshowed low but significant amountsof acetic acid, noaccumulation of formic acid, and lowersecretion of succinate andethanol. The maintenance of theplasmid pUC19 in themutant negatively affected metabolism.Expression of the pet operon overcame the metabolicstress caused by theplasmid, enhancing growth and glucoseuptake rates to the valuesobserved in the plasmidfreemutant. Also, expressionof the pet operon allowedconsumption of pyruvateaccumulated during the first hoursoffermentation.