PICHIA AND ZYGOPICHIA 281 



Species of Zygosaccharomj'ces and certain asporogenous yeasts 

 were also found to be responsible for the alcoholic fermentation of 

 musts (unfermented grape juice) abnormally high in sugar. In the 

 Rhine regions during warm and dry autumns, the grapes may become 

 overripe and shriveled ("Edelreif"). On these there frequently grow 

 certain molds. If either or both of these moldy and non-moldy sorts 

 of grapes make up a considerable portion of the crop, the must is 

 unusually rich in sugar, 30 to 60 per cent. The resulting wines 

 ("rheinische Ausleseweine") are quite different from the usual Rhine 

 wines. The grapes, the must, and the fermenting wines yielded a 

 large number of osmophilic yeasts, especially species of Zygosac- 

 charomyces which, rather than the ordinary wine yeasts, were re- 

 sponsible for the fermentation. These osmophilic yeasts are also in 

 many cases responsible for the spoilage of other products high in 

 sugar such as dried fruits, dates, and figs.^ 



Species of Zygosaccharomyces are frequently encountered and the 

 reader is referred to Stelling-Dekker for description of species. The 

 statement made in 1943 ^° that relatively few Zygosaccharomyces 

 are found in nature is not in accord with the experience of the au- 

 thors, and apparently not in accord with the publications of Lock- 

 head, ]\Irak, and others. A monographic treatment -°' -^ of the genus 

 is being published piecemeal by Nickerson, and no doubt this, when 

 completely published, will be the standard authority on Zygosac- 

 charomyces. 



Pichia and Zygopichia. (See Fig. 111.) These are among the 

 film-forming yeasts, that is, they tend to remain attached to" one 

 another after budding, and they grow in a pellicle on the surface of 

 liquid media. They also tend to be oxidative rather than fermentive, 

 and little alcohol but rather esters and carbon dioxide are produced. 

 Alcohol is usually utilized readily. Pichia and Zygopichia, as well 

 as asporogenous film-forming yeasts (which are possibly imperfect 

 forms of film-forming, sporogenous genera) , frequently cause a spoil- 

 age of fermented beverages in the later stages of the fermentation by 

 other yeasts. However, in some cases this secondary action of these 

 ester-producing yeasts is needed to provide the characteristic flavor 

 of certain wines, sherry, for example. These yeasts are also common 

 in pickle brine and can be readily isolated from the scum of ordinary 

 cucumber pickle brine during the initial salting, or from sauerkraut, 

 silage, dill pickles, and other foods whose acid comes from bacterial 

 lactic acid fermentation. Mrak and Bonar have made some careful 

 studies of these and other film-forming yeasts from a number of dif- 

 ferent kinds of pickle brine. A review_^ of the literature will be found 

 in their paper.* 



