WHAT IS THE PURE YEAST OF PASTEUR? 145 



C. The cells of Sacch. Pastorianus I. were present in large preponder- 

 ance ; only a doubtful trace of Carlsberg bottom yeast No. 2 was found. 



D. Sacch. ellipsoideus II. was in superabundance ; Sacch. cerevisia /. 

 could in this case also only be detected by cultivation in wort at 

 37-38 C. 



E. Both species sown, the brewery bottom yeast, and Sacck. ellip- 

 soideus II. were found, but the experiment showed that the latter 

 now formed half of the mixture, whilst at the commencement, as will 

 be remembered, it only constituted one-sixth ; the disease yeast had, 

 therefore, multiplied also in this case at the expense of the brewery 

 yeast. 



As the main result of this experiment it is found that the 

 two disease yeasts, Sacch. Pastorianus I. and Sacch. ellipsoideus 

 //., had suppressed the brewery yeasts. The first of them, as 

 has been already mentioned, imparts to beer a disagreeable 

 taste and odour, and the second produces in low fermentation 

 beers the disease known as yeast turbidity. The presence of 

 an excess of the brewery yeasts at the commencement of the 

 experiment was therefore of no avail. 



It will be remembered that in the lectures quoted above, 

 Velten bases his arguments entirely upon Pasteur's stand- 

 point, as enunciated in his ' Etudes sur la biere.' With him 

 the question was merely the removal of the bacteria. My 

 doctrine of the alcoholic ferments he disregards, and he con- 

 siders a brewery yeast to be pure when he has freed it from 

 bacteria. My investigations have, however, definitely proved 

 that the three species of Saccharomycetes, Sacch. Pastorianus 

 /., Sacch. Pastorianus III. and Sacch. ellipsoideus //., produce 

 diseases in low-fermentation beers (see the account in subse- 

 quent pages of this book). The correctness of my results has 

 been confirmed by Alfred Jorgensen, Gronlund, Will, Lasche, 

 Kokosinski, and others. It has been further proved in recent 

 years that in addition to those mentioned there are several 

 other Saccharomycetes which are able to produce diseases in 

 beer. Indeed, many facts point to there being a large 

 number of such species. The question whether a purification 

 of the brewery yeast has or has not been effected by its culti- 



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