Soybeans and wheat contain starch, a polymer of glucose. The microorganisms break down
starch to glucose, glucose to pyruvate via glycolysis, and—because the process is carried out in
the absence of O2 (i.e., it is a fermentation)—pyruvate to lactic acid and ethanol. If O2 were present, pyruvate would be oxidized to acetyl-CoA, then to CO2 and H2O. Some of the acetylCoA,
however, would also be hydrolyzed to acetic acid (vinegar) in the presence of oxygen.