A NOVEL FERMENTATION PATHWAY IN AN ESCHERICHIA-COLI MUTANT PRODUCING SUCCINIC ACID, ACETIC-ACID, AND ETHANOL

Escherichia coli strain NZN111, which is unable to grow fermentatively because of insertional inactivation of the genes encoding pyruvate: f ormate lyase and the fermentative lactate dehydrogenase, gave rise spo ntaneously to a chromosomal mutation that restored its ability to ferm ent glucose. The mutant strain, named AFP111, fermented glucose more s lowly than did its wild-type ancestor, strain W1485, and generated a v ery different spectrum of products. AFP111 produced succinic acid, ace tic acid, and ethanol in proportions of approx 2:1:1. Calculations of carbon and electron balances accounted fully for the observed products ; 1 mol of glucose was converted to 1 mol of succinic acid and 0.5 mol each of acetic acid and ethanol. The data support the emergence in E. coli of a novel succinic acid:acetic acid:ethanol fermentation pathwa y.