6io 



MICROBIOLOGY OF ALCOHOLIC FERMENTATION 



Slime-forming Bacteria. Musts and wines become slimy rarely 

 through the action of Dematium pullulans (Wortmann) and wild yeast 

 (Meisner) in the presence of oxygen but more frequently through the 

 action of bacteria. In most cases only young wines after fermentation 

 and when contained in closed casks or bottles exhibit this defect. A 

 slimy wine has an oily appearance, pours without splashing and in 

 extreme cases, becomes cloudy and will hang from a glass rod in strings. 



In such wines, the microscope reveals large numbers of almost 

 spherical or more or less elongated bacteria in long chains. Some ob- 

 servers have noticed a diplococcus and a sarcina. Kayser and Manceau 



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FIG. 156. Bacteria of slimy wine. A, B, C, Pure cultures of various forms; D, muci- 

 laginous sheath of slime bacteria. (After Kayser and Manceau.) ^ 



have recently investigated the subject very thoroughly and described a 

 number of forms which are mostly short rods of from IJJL to 2fj. by 0.7/4 

 to I.2/JL. One large form, 3/1 to 4^ X i.6/z to 1.7/1 was also noted. 

 They all form chains, usually of considerable length. They all produce 

 an abundant slimy sheath and stain easily with carbol-fuchsin and other 

 aniline dyes and are Gram-positive (Fig. 156). 



These bacteria attack the sugar but neither the glycerin nor the 

 alcohol and produce mannit, carbon dioxide, lactic and acetic acids and 

 ethyl alcohol. The disease is usually not serious and disappears under 

 the ordinary cellar treatment. Alcohol above 13 per cent, free tartaric 

 acid, tannin and sulphurous acid in small amounts prevent their 

 growth. 



Propionic and Lactic Bacteria. The most serious and perhaps 

 the commonest disease of wines is characterized by persistent cloudi- 

 ness, disagreeable odors and flavors, increase of volatile acid and 

 injury to the color or its complete destruction. Wines affected are 



