54 PHYSIOLOGY OF BACTERIA 



The origin of the extra amounts of CO2 in fermentation 

 by Bad. aerogenes (Rogers, Clark and Davis, 1914) is not 

 so easily accounted for. From the larger total volume of 

 gas produced, it does not seem that the increased 

 CO2 : H2 ratio of this group is due to a diversion of hydro- 

 gen; it appears more like an additional source of CO2. 

 An inter-reaction between methyl glyoxal and acet 

 aldehyde might be assumed, as in the case of the alcoholic 

 fermentation, but this would result in a larger amount of 

 alcohol, for which evidence seems to be lacking. 



Furthermore, this group shows the formation of acetyl- 

 methyl carbinol, probably according to reaction Ila, in 

 the aerogenes group, and of butylene glycol (reaction 

 IVf) in the colon group. 



Acetone Fermentation by spore-forming rods of the 

 type of B. macerans Schar dinger, and B. aceto-ethylicus 

 Northrop shows also a very varied list of products, adding 

 acetone to all the products observed in the colon-groups. 

 The types of reaction involved are the same as above 

 (la, lb, Illb, IVe, Ilia) and in addition, we have lie. 



lie: CH3COOH -I- CH3COOH = CH3'CO-CH2- COOH 



= CHa-CO-CHa + CO2 



The subgroup of B. asterosporus and B. polymyxa 

 Beijerinck forms butylene glycol besides alcohol, CO2 

 and H2. The origin of butylene glycol has already been 

 mentioned in the colon-typhoid group as being due to 

 reactions Ila and IVf while the rest of the products are 

 mainly produced by reactions lb and Ilia. 



Butyric Acid Fermentation probably starts with reac- 

 tion Ic, methylglyoxal giving acet aldehyde and formic 

 acid. The acet aldehyde goes through the aldol stage 

 and finally into butyric acid (reaction lib) 



lib. 2CH3CHO = C4H8O2 



