124 MICRO-ORGANISMS AND FERMENTATION. 



must-gelatine the colonies are round or sausage-shaped, white, 

 and non-liquefying. The species is facultative anaerobic, 

 and has its optimum for growth at 25-30 C. It decom- 

 poses laevulose and saccharose, and forms acetic acid, lactic 

 acid, and mannite. According to Miiller-Thurgau's observa- 

 tions, mannite fermentation occurs fairly frequently in fruit 

 wines, especially those prepared from over-ripe fruit, lacking 

 in acid. It is accompanied in fruit wines, as well as in grape 

 wine, by the formation of larger quantities of lactic and 

 acetic acid. 



In this connection a species must be mentioned which 

 plays an important part in the reduction of acid in wine. 

 According to Wortmann, Alfred Koch, and Seifert, certain 

 bacteria bring about this result, and Seifert has isolated a 

 species in pure culture. It is named MicrococciLS malolacticus, 

 and destroys part of the malic acid, the most important acid 

 of the wine, and forms lactic acid. As a consequence of the 

 activity of this bacterium, the wine loses its acidity, and 

 acquires a milder flavour, causing an improvement in its 

 quality. Like other organisms that destroy acid, its activity 

 is first displayed after the proper fermentation has ceased 

 and the yeast is in a weak condition. The species has its 

 optimum at 25-34 C., and the limits for its growth are at 

 34-37 C. It forms small milk-white transparent colonies 

 on nutrient gelatine. 



Other bacteria forming lactic acid and producing diseases 

 in wine are described by Maze and Pacottet, as well as by 

 Laborde, who has also investigated the mannite ferment. 



In leaven, lactic acid bacteria also occur which, without 

 doubt, play a part in the fermentation of bread. Peters, 

 for instance, found a species which occurs in motile rods, 

 and forms a slimy skin on neutral yeast-water-sugar at 30 C. 

 Henneberg found Leichmann's Bact. lactis acidi by development 

 in mash at 48 C., and at 38 C. a special species which he named 

 Bac. panis fermentati, which occurs in mash in short and long 

 rods, and forms small white colonies on wort-agar. The 

 optimum for the production of acid is at first about 37-42 

 C., and afterwards 34-38 C. Henneberg also found different 

 species of lactic acid organisms in pressed yeast along 



