356 MICRO-ORGANISMS AND FERMENTATION. 



Saceharomyces Bayanus Saccardo 



was discovered by Will in turbid beer. The cells are elliptical. 

 In old films strongly branching budding-colonies occur. The- 

 temperature limits for spore-formation are 32 and 0-5 C. ; 

 the optimum is 24 C. The limit for existence of the vegetative 

 cells in wort is 70 C. 



Besides causing yeast turbidity this species also imparts- 

 a sweetish, disagreeable, aromatic taste to beer, and an 

 unusually bitter herbal and astringent after-taste. The odour 

 is aromatic, like that of rotten fruit. With mixtures of about 

 29 per cent, of the wild yeast the flavour is very strongly 

 pronounced, and may be recognised even in the presence of 

 5 per cent. The yeast causes a discoloration of beer. It- 

 turns paler, and assumes a foxy appearance. 



Saceharomyces Logos Van Laer 



was derived from a yeast in Logos & Co/s brewery in Rio de- 

 Janeiro, and is a bottom-fermentation yeast of a Pastorianus 

 shape, which occurs in the fermenting vessel as a loosely-lying^ 

 sedimentary yeast of cheesy appearance ; consequently the- 

 beer clarifies very rapidly. The fermentation is carried out 

 at high temperatures (22 to 30 C.). The yeast ferments- 

 very slowly, but gradually produces very high percentages of 

 alcohol. The flavour of the beer is entirely different from that 

 of ordinary lager beer. According to Rothenbach this species 

 is able to ferment about half of a diastase-dextrin prepared 

 according to Lintner's recipe, but is distinguished from Schizo- 

 saccharomyces Pombe by fermenting other kinds of dextrin.. 

 According to Prior and Weigmann, it ferments Achroodextrin 

 III. (Prior) completely, whilst Achroodextrin II. is only fer- 

 mented to the extent of 75 per cent. 



Meissner determined the action of different acids on the 

 Logos yeast (in comparison with Saaz and Frohberg) using a 

 nutritive liquid consisting of 10 per cent, cane-sugar solution 

 with 10 per cent, of yeast-water. The fermentative activity 

 of Logos yeast was increased at first on the addition of 0-375 

 per cent, of acetic acid (the other two yeasts with 0-25 per 

 cent.). A smaller quantity of acetic acid (0-125 per cent.) 



