LACTIC ACID BACTERIA IN WINE. 123 



without, however, producing any considerable amount of 

 acid. It may occur in the form of long cells in lager beer. 



Schonfeld observed a species in various high-fermentation 

 beers, which looks like the bacterium of Berlin Weissbier, 

 and gives to these beers a slight lactic acid flavour, and may 

 make the beer membraneous. 



In the fermentation of wine lactic acid bacteria may 

 also occur, and may produce great alterations in the consti- 

 tution of the liquid. Amongst the better known phenomena 

 are " vin tourne " and " pousse " (lactic acid, Zickendwerden), 

 due to the presence of considerable quantities of lactic acid. 



Pasteur, as early as 1866, referred these diseases to the 

 activity of bacteria, and at a later date Muller-Thurgau proved 

 that a short bacillus regularly occurs in such wine, and is 

 capable of converting many of the constituents of the wine 

 into lactic acid, or of producing a lactic acid fermentation in 

 wine must. The disease declares itself in this way : The 

 wine becomes turbid, and is at first pale, afterwards dark, 

 and deposits a sediment. At the same time it assumes an 

 unpleasant smell and taste. The disease appears in those 

 seasons when the must is poor in acid, so that the bacteria 

 find more favourable conditions for growth. A bacterium 

 may be mentioned here that was isolated by Gayon and 

 Dubourg, a rod-shaped motionless organism which occurs 

 especially in red wine, and forms mannite (ferment mannitique), 

 whereby the wine assumes a characteristic bitter-sweet taste. 

 By the fermentation of different sugars it forms lactic acid, 

 acetic acid, etc., and only forms mannite by fermentation of 

 laevulose. It grows freely in dextrose and broth, and has its 

 optimum at about 35 C. By heating the wine to 60 C. its 

 development is restricted, and this is also the case if the 

 fermentation is vigorously carried out below 30 C. Like the 

 previous species its development is favoured by a wine with a 

 low acid content. By the addition of tartaric acid its growth 

 may be checked. Bact. mannitopceum, discovered by Muller- 

 Thurgau, belongs to this group. It forms the bacterial bubbles 

 described in an earlier section (zooglcea). It occurs in the 

 form of motionless rods, both long and short, and threads, 

 which may produce snow-white flecks in fruit wine. In 



