4i8 MYCODERMA. 



that it ceased to grow in wort in presence of 1.25 per cent, of 

 acetic acid, though vigorous growth occurred in the presence of 

 i per cent., four-fifths of the acid being consumed in ten days 

 at 30 C. 



The simultaneous formation of acid by Mycoderma has been 

 demonstrated by the total acidity of the medium being maintained 

 in several of the nutrient media tried, notwithstanding the con- 

 sumption of the organic acids supplied. In other instances the 

 reduction of total acidity was slight, although energetic growth 

 of the vegetation was observed, 



The various Mycoderma produce different volatile acids, which 

 can be identified by the odour of the nutrient liquids. According 

 to WORTMANN (XVII.), many mouldy wines smell strongly of 

 rancid butter, owing to the presence of butyric acid formed by 

 the action of the Mycoderma on different constituents of must 

 and wine. As long ago as 1893, LAFAR (III.) isolated a film- 

 producing budding fungus, containing Mycoderma cerevisice in 

 the involutions of the film, from the cask sludge of a brewery 

 where difficulties were of frequent occurrence. The beer on which 

 the cultures were grown exhibited an agreeable, fruity smell, and, 

 after turning sour, a pleasant taste recalling that of wine vinegar. 

 WILL (XIII.) also noticed extensive production of acid in the 

 pale Munich beer on which his Mycoderma cultures were grown. 

 " On opening the culture vessel (he says) one noticed a sour smell, 

 at first similar to that of acetic acid, but afterwards more difficult 

 to define, being something like baked apples. The beer had 

 a decidedly sour taste ; but not of acetic acid." It should be 

 mentioned that WILL (XIII.) cites the authority of Raymond 

 and Kruis for the statement that formic acid and acetic acid 

 were discovered in a culture of Mycoderma that had been standing 

 for a year at 20 0. 



In addition to volatile acids, the Mycoderma produce fixed 

 acids and esters, as is shown by the fact that the volatile acids 

 formed are insufficient in quantity to account for the difference 

 in the total acidity when an increase occurs in the acidity of 

 the nutrient liquid. GRAF (II.) mentions that the Mycoderma 

 cerevisice examined by him causes increased acidity in sterilised 

 wort, the acid content rising in twenty-eight days from 5.7 c.c. to 

 8.5 c.c. in terms of decinormal baryta water. The Egyptian 

 beverage *' Leben," of the kephir type, contains a Mycoderma 

 lebenis, discovered by HIST and KHOURY (I.), that produces fixed 

 acids and acetic acid. WILL (XIII.) assumes that the production 

 of acid is the cause of the decoloration of top -fermentation beer 

 when contaminated by large quantities of the Mycoderma species 

 examined by him. 



