FERMENTATION OF DEXTRIN BY YEAST. 541 



doned them on discovering Logos yeast. He then distinguished 

 between the types S, F, and Logos, as well as the subsequently 

 discredited intermediate types, Saaz-Frohberg and Frohberg- 

 Logos. 



A new type was discovered by LINDNER (XXX.) in Schizos. 

 Pombe (see p. 293, vol. ii.), which is able to carry the fermenta- 

 tion of wort further than is the case with Logos yeast. This 

 yeast has been exhaustively studied by W. WINDISCH (VI.) and 



F. ROTHENBACH (I.). 



Consequently we have the following four types of yeast : S, 

 F, Logos, and Pombe. The differences of attenuation produced 

 by these yeasts are undoubtedly due to the fact that some of 

 them are able to ferment dextrins, in addition to maltose (and 

 hexoses). This faculty has been proved in the case of Logos 

 yeast and Schizos. Pombe, though the cause of the difference 

 between the types S and F has not yet been established on a 

 scientific basis. It is true that numerous workers, especially 

 PRIOR (VII.), have occupied themselves with this problem ; but, 

 up to the present, the researches and hypotheses of Prior, and 

 also those of BAU (XXXII.), have not led to any final and recog- 

 nised result. 



The direct examination of the fermentability of dextrin by 

 pure cultures of yeast was performed by LINDNER (XXXV.), who 

 obtained the surprising result that many species ferment dextrin 

 in a greater or smaller degree, even yeasts of the Saaz type being 

 found by the same author (XLVII.) to be capable of attacking 

 dextrin, namely, the top-fermentation OS yeasts, Nos. 150, 159, 160 

 and 403. On the other hand, Saaz yeast itself, and various other 

 races belonging to the OS and US types, do not ferment dextrin. 

 Certain other top-fermentation beer yeasts of the OF type, includ- 

 ing Burton yeast, attack dextrin ; and indeed, out of forty yeasts 

 of this type examined, only eight left the dextrin intact. 



Nearly all top yeasts from pressed-yeast factories ferment dex- 

 trin energetically, only one yeast from Bavaria, out of thirteen races 

 examined, giving a doubtful result compare LINDNER (XLVII.). 



The true distillery yeasts, on the other hand, have, in general, 

 little or no fermentative power on dextrin, 50 per cent, of the 

 races examined leaving this carbohydrate intact. 



Out of thirty-three low-fermentation beer yeasts, only one 

 fermented dextrin energetically, another slightly; and in the 

 case of fourteen races the result was doubtful compare LINDNER 

 (XLVII.), who also reports that a few races of wine yeast can 

 ferment dextrin. 



The film yeasts examined by Lindner have no action on 

 dextrin ; but, on the other hand, the species of the genus Willia 

 (see p. 289, vol. ii.) seem to attack this carbohydrate slightly, only 

 one species, W. belgica, giving decidedly negative results. 



The wild yeasts with botanical names, S. Pastor ianus /., //., 



