Enzymatic Studies on the Oxidation of Sugar and Sugar Alcohol |
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Authors: | Kiyoshi Sato Yuzo Yamada Kô Aida Teijiro Uemura |
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Affiliation: | Institute of Applied Microbiology, The University of Tokyo, Bunkyo-ku, Tokyo |
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Abstract: | During the course of studies on the oxidative metabolism of d-sorbitol by acetic acid bacteria, it was found that d-sorbitol was almost quantitatively converted to 5-keto-d-fructose via l-sorbose by a certain strain of Gluconobacter suboxydans. In addition to 5-keto-d-fructose, three γ-pyrone compounds, kojic acid, 5-oxymaltol, and 3-oxykojic acid, 2-keto-l-gulonate, and several organic acids such as succinic, glycolic, and glyceric acids were confirmed in the culture filtrate of this bacterium. The most suitable carbon source for 5-ketofructose fermentation by Gluconobacter suboxydans Strain 1 was confirmed to be d-sorbitol or l-sorbose using growing and resting cells. d-Fructose had little effect on the formation of this dicarbonylhexose. The optimal pH for the formation from l-sorbose by intact cells was found to be at 4.2. The activity of the pentose phosphate cycle in the resting cells was calculated as 13~17 μatoms/hr/mg of dry cells by the use of the manometric techniques. There was no strain tested so far which could accumulate a large amount of 5- keto-d-fructose from d-sorbitol except this bacterium. The experimental results shown in this paper makes the prediction that a certain dehydrogenating system of l-sorbose is functional in the organism, and the metabolic pathways of d-sorbitol via l-sorbose and 5-keto-d-fructose is proposed.
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