Oxidation-Reduction Studies on the 2,3-Butylene Glycol-Acetyl-Methyl-Carbinol System in a Fermentation

Abstract

Dissimilation of glucose is brought about by bacteria of the genus Aerobacter and among the products of fermentation are acetyl-methyl-carbinol and its reduction product, 2, 3-butylene glycol. It has been suggested that these substances form a reversible oxidation-reduction system. In this case the methylene blue may replace the acetyl-methyl-carbinol as a hydrogen acceptor providing its redox potential lies above that of the carbinol-glycol system. The substances acting as hydrogen donators include the reduced constituents of all the reversible systems present in fermentations whose electrode values lie below that of methylene blue. In 2, 3-butylene glycol fermentations, lactic acid might be expected to donate hydrogen and form pyruvic acid. If 2, 3-butylene glycol is involved in a reversible system whose electrode potential value is below that of methylene blue, the addition of methylene blue to the fermenting mixture will reduce the concentration of 2, 3-butylene glycol and increase concentration of acetyl-methyl-carbinol.

The medium used was 0.2 molar glucose solution containing 1 gm. of ammonium chloride and 1 gm. of dipotassium phosphate per liter. The pH was held constant by the addition of 10 gm. of calcium carbonate to each liter of fermenting medium. The fermentation took place under anaerobic conditions produced by a continuous stream of CO₂ bubbling through the medium. The organisms used were Aerobacter indologenes, A. salicinovorum and A. decolorans.

When 2/3 of the glucose was fermented, a known quantity of methylene blue was added to the fermentation. Samples were withdrawn after the addition of various amounts of methylene blue and the 2, 3-butylene glycol, acetyl-methyl-carbinol and glucose were determined. The results of these analyses are shown in Table I.

The results seem to show that the 2, 3-butylene glycol does not act as a hydrogen donator to methylene blue under the conditions of this experiment and hence cannot be included in a reversible system.