LOW-FERMENTATION YEASTS. 325 



P. Lindner distinguished two species of low-fermentation 

 yeast in 1889, which he called " Saaz " (weakly fermenting) 

 -and " Frohberg " (strongly fermenting). These names have 

 been adopted in the literature as a description of weakly and 

 strongly fermenting yeast types in general. The investigation 

 of these groups was subsequently undertaken by Delbriick, 

 Reinke, Irmisch, and others. 



A thorough description of two low-fermentation yeasts of 

 the Frohberg type (D and K) has been given by Schonfeld and 

 Rommel. D gives longish, almost sausage-shaped cells, K 

 predominantly spherical and oval cells. I) is more inclined 

 to form spores than K. In hanging drops, differences in the 

 shape and size of the cells can be remarked. K forms budding 

 colonies more rapidly and in greater number. In the growth 

 of giant colonies similar differences have been observed. The 

 content of albumen, the percentage of ash and phosphoric 

 acid are higher in K than in D, and K has a higher specific 

 gravity than D. Auto-digestion occurs more rapidly with K. 

 K has a higher " raising power," and is more sensitive to high 

 temperatures. Fermentation sets in more rapidly with K. At 

 temperatures above 30 the fermentative activity of K yeast 

 is weakened to a much greater extent than that of D. The 

 film growth of K is capable of fermenting more carbohydrate 

 than the sedimentary yeast, whilst with D the difference is 

 unimportant. In the brewery, K ferments 10 per cent, higher 

 than D in the fermenting vessel, and gives a lighter coloured 

 beer. The final fermentation is identical with the two species. 



In 1883-85 very detailed researches were carried out by 

 the author in elaborating the principle laid down by Hansen, 

 and introduced in the Carlsberg brewery, the application of 

 methodically selected pure cultures derived from a single 

 cell. The experiments were carried out with a view of 

 securing practical conditions, and the results gained in the 

 laboratory were applied on the large scale in breweries in 

 many European countries. The reform found acceptance by 

 prominent fermentation technologists (in the early stages, 

 especially by Thausing, Lintner, and Aubry), and it was 

 gradually incorporated into the courses of all zymotechno- 

 logical institutes. 



