84 BACTERIAL METABOLISM PRODUCTS 



Wohl has developed a theoretical scheme of reactions by which 

 the process of alcoholic fermentation could be represented. In the 

 first place the elements of water are removed from the oc and /3 

 carbon atoms of glucose (I) and the resulting enol (II) undergoes 

 conversion into the corresponding keton (III), which has the consti- 

 tution of a condensation product of methylglyoxal and glyceral- 

 dehyde, and hence is readily resolved by hydrolysis into these com- 

 pounds (IV). The glyceraldehyde passes by a similar series of 

 changes (V, VI) into methylglyoxal, and this is then converted by 

 addition of water into lactic acid (VII), a reaction common to all 

 ketoaldehydes of this kind. Finally, the lactic acid is split up into 

 alcohol and carbon dioxid (VIII). 



In alcoholic fermentation there also results small quantities 

 (0.1 to 0.7 per cent.) of fusel oil. This contains normal propyl 

 alcohol, primary isobutyl alcohol, primary iso-amyl alcohol, and the 

 optically active (primary) iso-amyl alcohol. It was thought at 

 one time that these resulted from the fermentation of the glucose, 

 but Ehrlich in a series of masterly researches, shows conclusively 

 that their origin is the amino-acid which result from the hydrolysis 

 of the proteins, the reactions of which may be given as follows: 



i 



(CH 3 )2 CH CH2- T -CHNH 2 COOH+H2O-(CH 3 )2 r -CHCH2CH2OH+C02+NH 3 

 Leucine. Primary isobutyl alcohol. 



II 



CH 3 CH(C2H 6 ) CH(NHV)COOH + H 2 O - CHsCH^HsCI^OH + CO 2 + NH 3 

 Isoleucine. Primary iso-amyl alcohol. 



Succinic acid also occurs among the products resulting from alco- 

 holic fermentation of sugar and has its origin in the amino-acids. It 

 results when aspartic acid is acted upon by putrefactive bacteria- 



COOH CH2 CH NHaCOOH + H 2 =COOH CH 2 CH 2 COOH -f NHs 



This, however, differs from the first reaction in that it is a process 

 of partial reduction and not hydrolysis. 



Other bacteria have been studied which possess the power of pro- 

 ducing butyl and amyl alcohol from carbohydrates. It is still an 

 open question to what extent the amyl alcohol (fusel oil) produced 

 during an impure alcoholic fermentation is due to bacteria, for it 

 is known that some alcohol yeasts possess the power of decomposing 

 two protein decomposition products, leucin and isoleucin, with the 

 production of fusel oil. 



4. Acid Production. In general it may be stated that an acid 

 reaction is caused by the fermentation of one of the sugars, glycerin, 

 or a similar substance in the nutrient media. It is one of the more 

 constant physiologic characteristics of bacteria, and in addition to 



