ZYMASE 491 



gested by Neuberg that the action of the sodium sulphite is 

 to combine with the acetic aldehyde as soon as it is formed, 

 thus preventing it from acting as an hydrogen acceptor ; some 

 other three carbon compound of unknown composition then 

 functions in its stead producing glycerol as follows : — 



CsHeOa + 2H = CjHgOa 



The effect of the added sulphite is, therefore, to produce a 

 modification of the original Gay Lussac equation to account 

 for the production of acetic aldehyde and glycerol as follows : — 



CeHiaOe = CO2 + CH3CHO + C3H5(OH)3 



If it is desired to represent the action of the sulphite, the 

 equation becomes- — - 



CfiHiaOe + NagSOg + U^O = NaHCOj + CH3CHO . NaHSOg + CgHgOa 



Neuberg and Reinfurth * describe the following experi- 

 ment for demonstrating the production of acetic aldehyde 

 during alcoholic fermentation. Two tubes containing 20 c.c. 

 of 10 per cent cane sugar or glucose are shaken up with 

 2 gms. of yeast and to one tube are added 2 gms. of calcium 

 sulphite (prepared by double decomposition from sodium 

 sulphite and calcium chloride, cf. p. 1690). The two tubes 

 are then immersed in a water bath at 38-40°. After a 

 quarter of an hour acetic aldehyde can be demonstrated in 

 the tube containing the sulphite by removing 3 c.c. and 

 adding to them, without filtering, 0"5 c.c. of 4 per cent 

 sodium nitroprusside solution and 2-3 c.c. of 3 per cent 

 piperidine solution, when a deep blue colour indicating acetic 

 aldehyde is produced. The control solution gives no colour 

 under the same conditions. 



A third mode of fermentation is that produced in the 

 presence of alkaline salts such as ammonium carbonate or 

 other soluble carbonates or phosphates. In this case the 

 acetic aldehyde, produced as before, is acted upon by an en- 

 zyme known as aldehyde mutase which causes it to undergo 

 a Cannizzaro reaction, producing acetic acid and ethyl alcohol 

 as follows : — 



CH3CH0 O 



II ~> CH3COOH + CH3CH2OH 

 CH3CH0 H2 



♦Neuberg and Reinfurth : " Ber. deut. chem. Gesells.," 1919, 52, 1677. 



