Studies on Lactic Acid Fermentation

Part III. Mechanism of Ethanol Formation

Abstract

1. Pyruvate and acetaldehyde were detected as intermediates in the pathway of heterolactic fermentation by L. fermenti.
2. Acetaldehyde was accumulated aerobically as an oxidation product of ethanol in the pre-sence of semicarbazide.
3. Dismutation of acetaldehyde to ethanol and acetate was observed when acetaldehyde was added to the system of glucose fermenta-tion.
4. Alcohol dehydrogenase in an ammonium sulfate fraction catalyzes both DPN- and TPN-dependent oxidation of ethanol to acetaldehyde. Acetyl CoA was reduced in the presence of either TPN or DPN with the same fraction.
5. By coupling of D-xylose degradation with mannitol utilization appreciable increase of ethyl alcohol was observed with resting cells of heterolactic microorganisms.
6. With the continuous supply of reduced methyl viologen approximately half molarity of acetate to be produced from D-xylose was transformed to ethyl alcohol in an absolutely anaerobic condition. From L-arabinose only poor amount of ethyl alcohol was produced by both strains of microorganisms.
7. A metabolic pathway of lactic acid fer-mentation including D-mannitol fermentation was suggested.