MYCODERMA VINI 331 



MYCODERMA CEREVISIAE. Desm, Hansen 



Described by Hansen l after finding it in the breweries of Copen- 

 hagen this yeast possesses cells of varied shapes. Ordinarily the cells 

 are transparent. Each cell usually contains one to three small re- 

 fractive granules (Fig. 146). On beer wort, this yeast produces a 

 dull gray scum frequently folded. It does not invert saccharose and 

 gives no fermentation. On beer wort gelatin, spots of a gray color 

 are formed. Mycoderma cerevisiae forms its sc ms between 2 and 15 C. 

 and up to 33 C. It may cause considerable damage in beer which 

 it attacks. 



Hansen was the first to show that this yeast is not a well-defined 

 species but rather a group of species which has been confirmed later 

 by Lasche*. This author describes four 

 species which are distinguished from the 

 yeast described by Hansen in that in beer 

 wort, they produce alcohol, one 0.26 per 

 cent by volume, two others 0.79 per cent 

 and a third 0.51 per cent. All of these 

 cause disease in beer. Lafar has dis- 

 covered another Mycoderma very closely 

 related to the latter which forms a scum 

 quite closely related to that formed by Fig. 1 46. Mycoderma cerevisiae 

 Mycoderma* cerevisiae and which gives ^ a S^ inCopenh '' eel1 

 acetic acid. 



H. Leberle and Will have described two species of Mycoderma 

 cerevisiae. The first Mycoderma cerevisiae, var. a has cylindrical cells 

 sometimes elongated (2-3 ju wide and 7-10 ju long). The giant colonies 

 are very uniform. The temperature limits for vegetative growth are: 

 7-30 and the optimum 20-25 C. This species assimilates only levu- 

 lose. It oxidizes alcohol quite energetically and assimilates organic 

 acids easily. 



The second Mycoderma cerevisiae var. c, possesses oval cells or 

 cylindrical cells (2-4 /i wide and 6 to 10 ju long). The temperature 

 limits for growth are: 7 C. and 30 C. The optimum is 20-25 C. 

 This species assimilated glucose and levulose; like variety a it acts 

 towards alcohol and organic acids. 



MYCODERMA VINI. Desm 



This species has been described by Seynes, Wortmann and Wino- 

 gradsky. It presents some of the characters of Mycoderma cerevisiae. 



1 Hansen, E. C. Levures alcooliques ressemblant a des Saccharomyces. 

 Comp. Rend, des trav. du lab. de Carlsberg, 2, 1888. 



