464 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



of the saccharose and rendering the crystallization difficult and by forming 

 gelatinous masses in the liquids. 



Many of them are very resistant to heat. S. zopfii withstands a tem- 

 perature of 66 for half an hour. Streptococcus mesenterioides forms chains 

 of cocci surrounded by voluminous gelatinous sheaths which unite in 

 zoogloeic aggregations sometimes very troublesome in sugar factories. 

 On account of its sheath it is very resistant to adverse conditions. It 

 retains its vitality after drying for three and a half years. It is not killed 

 by heating to 86 for five minutes and occurs in the hot liquids of the 

 diffusion batteries. 



TOBACCO. If tobacco leaves are simply dried they do not contain 

 the aromas desired by smokers; they contain large amounts of protein 

 substances that give a bad odor to the smoke and they are often too rich 

 in nicotin. 



To overcome these defects the dried leaves are piled in masses, 

 moistened and allowed to undergo a fermentation which raises the tem- 

 perature to 50 to 55. Sometimes the leaves are then sprinkled with 

 a solution containing sugar, honey, various aromatic substances and 

 sometimes alcohol and passed through another fermentation. 



The leaves are then tied up in bundles, partially dried, and pressed 

 into boxes where another slow fermentation often takes place. 



The principal chemical changes which take place in this "curing" 

 of tobacco are a considerable diminution of the nicotin, the destruction 

 of nitrates and the production of ammonia and sometimes of butyric 

 acid. 



There are three theories as to the cause of these changes. According 

 to Suchsland they are due to bacterial activities and by the use of pure 

 cultures he claims to have much improved ordinary tobacco. 



According to Nessler and Schlossing the bacteria are useful only in 

 raising the temperature of tJne mass which is thus made more subject 

 to the action of atmospheric oxygen. This is the immediate cause of 

 the chemical changes. 



The third theory is that of Loew who ascribes the changes to the 

 action of enzymes, oxidases, peroxidases and catalases existing in the 

 leaves of the tobacco. 



It seems probable, according to many investigators, that the changes 

 are due in the first place to hydrolyzing, proteolytic and oxidizing enzymes, 

 and that these diastatic transformations are supplemented by the bacteria 



