1940 HA Krebs citric acid cycle theory put forward since the mechanism of citric acid fermentation gradually been recognized. Has proved that sugar, citric acid and biochemical quality of raw materials generated during the process of pyruvate by the sugar into alcohol fermentation with the same, that is, through the EM channels (channel pairs hexose phosphate) for glycolysis, and pyruvate Further oxidation of acetyl-CoA decarboxylation A, acetyl coenzyme A and pyruvate carboxylation generated by the condensation of oxaloacetate into citric acid and enter the citric acid cycle ways.