THE ANAEROBIC DISSIMILATION OF D-RIBOSE-1-C14, D-XYLOSE-1-C14, D-XYLOSE-2-C14, AND D-XYLOSE-5-C14 BY AEROBACTER AEROGENES

Abstract

The lactic acid produced from D-ribose-1-C14 or D-xylose-1-C14 has only a trace of isotopic C in the carbinol group, while the methyl C has 40% and the carboxyl C 20% of the specific activity of carbon-1 of the pentose. The lactic acid from D-xylose-2-C14 is labeled to a slight extent in the methyl group, while the carbinol C and the carboxyl C have 40% and 20% respectively of the C14 concentration of C-2 of the sugar. D-Xylose-5-C14 yields lactic acid labeled mainly in the methyl C, which has about 60% of the specific activity of C-5 of the pentose. The other fermentation products (2,3-butanediol, ethanol, acetic acid, formic acid, and CO2) are labeled as if they were formed from pyruvate with the same labelling as the lactic acid. These results offer additional support to the hypothesis whereby complete conversion of pentose to triose occurs via a heptulose.