ZYMOGENIC BACTERIA 2 09 



Many alcoholic liquids may be oxidized to form acetic acid, 

 carbon dioxide, and water, or may be oxidized directly into 

 water and carbon dioxide without any acid formation. 



Maximum acetic acid fermentation takes place at a tem- 

 perature of about 35 C. and ceases at 45 C. and 5 C. to -5 C. 

 In a concentration of fourteen per cent (14 per cent) acetic 

 acid inhibits all bacterial growth. 



Acetic fermentation is very prominent in the vinegar indus- 

 tries in some countries. The alcoholic liquids, such as cider, 

 wine, etc., are brought in contact with acetic acid bacteria 

 and also with a free supply of oxygen (air) , and by this process 

 are oxidized. 



Acetic acid is formed in practically all fermentive processes 

 (lactic, butyric, acetic, etc.). The species of bacteria which 

 are able to produce acetic acid are not so numerous as the 

 lactic acid bacteria. Bacillus acetici is a common form. The 

 process is aerobic. The bacteria cannot produce acid in the 

 absence of alcohol. It is probable that the carbon of the 

 alcohol serves as a food. 



Butyric Acid Fermentation. The formation of butyric 

 acid by the enzymes of bacteria is a process which is quite 

 widely distributed. The fermentation is carried on only 

 under strictly anaerobic conditions. At one time it was 

 thought that lactic and butyric fermentations were due to 

 enzymes of the same bacteria (Amylobacter butyricus). It 

 has since been proved that specific bacteria are the cause of 

 the major portion of these fermentations. About twenty 



