THE FERMENTATION OF THREE CARBON SUBSTRATES BY CLOSTRIDIUM PROPIONICUM AND PROPIONIBACTERIUM

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Abstract
Clostridium priopionicum reduces lactate-3-C14 to propionate-3-C 14 . Ace-tate is labeled only in the methyl C. When lactate-3-C14 is fer-mented by Propionibacterium arabinosum, propionate is labeled mainly in the 2- and 3- C but some tracer is found in the carboxyl C and CO2. Both C''s of the acetate are labeled, the methyl C higher than the carboxyl C. A similar distribution of tracer in propionate was found when lactate, pyruvate, or glycerol is labeled in the 2-C. In these latter fermentations, acetate is labeled highest in the carboxyl group. The quantitative relationship of the end products and the C14 data indicate that succinate and propionate may be formed in part by a condensation reaction, perhaps via citrate.