220 H. G. WOOD, F. W. LEAVER VOL. 12 (1953) 



mixed melting point and by the isotope dilution method. No attempt was made to obtain carbon 

 balances in the fermentations reported in Tables VIII and IX. The propionate and succinate were 

 obtained by chromatogramming aliquots of the volatile and non-volatile acids and they were purified 

 by the procedure given above. 



Degradation procedures 



The propionic acid was degraded by a modification of the procedure described by Wood et al.^^. 

 1.5 to 2.0 mM of sodium propionate were dried for 3 h at 120 ° to 130° C. One ml of benzoyl chloride 

 and 0.5 ml of bromine were added and refiuxed for 2 hrs. Eighty to 100 ml of water followed by 7 g 

 of potassium carbonate were then added to the mixture. This mixture was then refiuxed for 7 h to 

 obtain lactic acid. The lactic acid was then degraded by the method of Wood et al^'^. 



The degradation of succinate was accomplished by the Schmidt reaction. 0.3 to 0.5 mAf of 

 succinic acid and 2 ml of phosphoric acid (47 g of PgOj and 100 ml of go %. H3PO4) were placed in 

 an apparatus similar to that described by Phares^^ for degrading volatile acids by the Schmidt 

 reaction. Fifty mg of sodium azide which had been activated by treatment with acetone were added 

 and the mixture was heated at 60'' C for 30 min. The reaction vessel was then heated on a steam bath 

 for 3 h. This procedure was repeated two more times adding 50 mg of sodium azide each time. A 40-50 

 per cent, yield of the carboxyl groups was obtained. 



Total oxidation of any material was accomplished by use of the wet combustion mixture as 

 described by Van Slyke^^. 



All samples were counted as barium carbonate using an end window Geiger-Muller tube. 



The authors wish to express their apprecication to Mr Rune Sternholm for assis- 

 tance in some of the degradations. 



SUMMARY 



The fermentation of 3, 4, 5 and 6 carbon compounds by the propionic acid bacteria have been 

 investigated by quantitative determination of the products and by estimating the COj turnover and 

 distributuon of the fixed COj in the products. It has been found that there is a remarkable similarity 

 in the quantitative relationship of the products of all the substrates, which is independent of the length 

 of the carbon chain. If a cleavage of the 4 or 5 carbon substrates to C^ or Cg compounds occurs, 

 these cleavage products are largely converted to succinate and propionate by secondary reactions. 

 The COg turnover was quite low and did not indicate thatCOj is formed as a primary cleavage product 

 from erythritol or adonitol. With these substrates, the distribution of fixed COg in the products was 

 identical to that found from C3 and C^ compounds and thus no evidence of a unique mechanism of 

 fermentation was obtained by this method. 



COg turnover was investigated in relation to the problem of the mechanism of formation of 

 propionate. Under certain conditions, it was found that the COg turnover was much lower than that 

 required by a mechanism in which succinate is decarboxylated to propionate and COg. It is suggested 

 that the formation of propionate from a C^ dicarboxylic acid may involve a "C^" which is not COg 

 but may be converted to COg. 



Considerable variation has been found in the ability of different cell preparations to fix COg. 

 The best fixation was obtained with cells grown on a glycerol, yeast extract, phosphate, vitamin-B 

 medium. NaF inhibits completely the net fixation of COj but it docs not prevent the incorporation of 

 ^^COg into the propionate and succinate. 



RfiSUMfi 



Les auteurs ont etudie la fermentation des corps en Cg, C4, C5 et Cg par les bacteries propioniques 

 en dosant les produits formees et en determinant la vitcssc de renouvellement du COj et la distri- 

 bution du CO2 fix6 dans ces produits. II y a une similitude rcmanpiable dans la proportion des produits 

 formes a partir de tous les substrats, quelle que soit la longueur de leur chainc carbonee. Si les pro- 

 duits en C4 ou C5 se clivent en donnant des produits en C^ ou Cg, ces produits de clivage sont en grande 

 partie transform(5s en succinate et en propionate par des r(5actions sccondaircs. La vitessc de renou- 

 vellement du COg est tres faible et 'nindique pas que COg soit le produit de clivage primaire de I'ery- 

 thritol ou de I'adonitol. Avec ces substrats, la distribution du COg fix6 dans les produits form6s est 

 identique a celle que Ton trouvc avec des corps en C3 ct en Cg. Cette methode ne donne done pas la 

 l^reuve que la m^canisme de fermentation est unique. 



References p. 221I222. 



