314 BACTERIOLOGICAL CHEMISTRY 



Although acetoacetic acid may be derived by condensa- 

 tion of acetic acid it seems unnecessary to postulate that 

 the acetic acid is formed via aldol when it is known that 

 acetaldehyde can give rise to it and ethyl alcohol by 

 dismutation in presence of the enzyme aldehydemutase. 



Butyl Alcohol-Acetone Fermentation. — The production 

 of acetone by fermentation processes was initiated during 

 the 1914-1918 war period, when it was required in large 

 quantities for the manufacture of explosives. The fer- 

 mentation has undergone even greater development since 

 that time as a result of the greatly increased use of butyl 

 alcohol and acetone as solvents for lacquers and in the 

 form of esters as plasticisers in the cellulose paints and 

 varnishes and in cellophane preparation. When the 

 process was developed in this country and the United 

 States in 1915 the butyl alcohol was a by-product for 

 which no market could be found ; nowadays it is the 

 more valuable of the two products. 



The organisms responsible for the production of these 

 solvents from starch and sugars are spore -bearing soil 

 organisms of the type CI. aceto-butylicum, which are 

 similar to the flax-retting organisms. Two groups of 

 these organisms are recognised. One group produces the 

 organic acids, butyric and acetic acids, but cannot ferment 

 them further to the neutral products butyl and ethyl 

 alcohols and acetone ; to this group belong the true 

 butyric acid bacteria such as CI. hiityricum. The second 

 group comprises the butyl alcohol bacteria which, under 

 favourable conditions of the medium, reduce the inter- 

 mediately formed acetic and butyric acids to ethyl alcohol, 

 acetone and butyl alcohol. Some of these organisms, for 

 example, CI. butyricum, require the medium to be main- 

 tained neutral by the addition of calcium carbonate in 

 order tliat they may bring about fermentation. For 

 others, like CI. aceto-hutyliciwt,, the addition of calcium 

 carbonate is unnecessary or even undesirable. 



