ALCOHOLIC FERMENTATION 383 



CH 2 OH . CHOH . CHOH . CHOH . CHOH . CHO = 



CH 2 OH . CHOH . CHO + CH 2 OH . CO . CH 2 OH 

 glyceric aldehyde dihydroxyacetone 



The two latter compounds by the loss of one molecule of 

 water would each yield methyl-glyoxal. 



CH 2 OH . CHOH . CHO - H 2 O \ CH 3 CO . CHO 

 CH 2 OH . CO . CH 2 OH - H 2 O / methyl-glyoxal 



From these two molecules of methyl-glycoxal, molecular 

 proportions of glycerol and pyruvic acid would result from the 

 simultaneous oxydizing and reducing and hydrolytic action 

 of two molecules of water. 



CH 2 =COH.CHO H 2 CH 2 OH.CHOH.CH 2 OH 



+ II = + 



CH 3 . CO . CHO 6 CH 3 . CO . COOH 



pyruvic acid 



The pyruvic acid is then acted upon by a carboxylase in 

 the yeast yielding acetic aldehyde and carbon dioxide. 

 CH 3 . CO . COOH . = CH 3 CHO + CO 2 



Another molecule of water simultaneously reduces the 

 aldehyde to ethyl alcohol, and oxidizes a fresh molecule of 

 methyl-glycoxal to pyruvic acid. 



CH 3 . CHO H 2 CH 3 CH 2 OH 



+ II = + 



CH 3 .CO.CHO O CH 3 .CO.COOH 



It was found by these same authors * that if sodium sulphite 

 were added to the fermenting mixture, so that the acetic 

 aldehyde formed as above is fixed at once in the form of its 

 bisulphite addition compound, it is not further reduced, and 

 the hydrogen which thus becomes avaible is used in produc- 

 ing glycerol by the reduction, presumably, of the glyceric 

 aldehyde. According to theory, a glucose molecule could 

 yield one molecule of glycerol and one molecule of acet- 

 aldehyde : 



CeH^Og + Na 2 S0 3 + H 2 O = C 3 H 8 O 3 + CH 3 . CHOH . SO 3 Na + HNaCO 3 



About 70 per cent of this theoretical yield of glycerol was 

 obtained, which corresponds to about 35 per cent of the glu- 

 cose employed. 



* Neuberg and Reinfurth : " Biochem. Zeitsch.," 1918, 89, 365. 



