70 MICRO-ORGANISMS AND FERMENTATION. 



those which occur in largest numbers in the flasks. Penicillium 

 glaucum and Mucor stolonifer were found among them. 



Next to the moulds come the bacteria when wort is infected 

 with water, whilst if sterilised beer is used, they develop 

 only scantily. The following bacterial forms were found : 

 Bacterium aceti, Bact. Pastorianum, a third form which made 

 the beer slimy and ropy ; and lastly, several species which 

 imparted a disgusting smell to the wort. 



Yeast-like cells were of rare occurrence. Holm did not 

 observe any growth of Saccharomycetes, although some Torula 

 forms and Mycoderma occurred. 



The number of these germs varied at different times of 

 the year, yet it did not seem to be dependent on the season 

 the rainfall, the condition of the surface water, and of the 

 air had great influence. Of practical importance was the 

 discovery of strong contaminations injurious to wort and 

 beer, in reservoirs situated near granaries and malt-lofts 

 insufficiently protected against dust. It was also shown 

 that water which had been filtered through charcoal filters 

 contained much larger numbers of wort bacteria than the 

 unfiltered water. 



The water analyses made in the author's laboratory during 

 a period of more than twenty years have given the following 

 chief results : The samples of water in only very few cases 

 were found to contain Saccharomycetes (culture yeasts or 

 wild yeasts). In one series of analyses S. anomalus and S. 

 membranes faciens were met with. The bacteria observed by 

 Holm which produced slime formation or imparted a putrid 

 smell to the wort, occurred very frequently. If a pure yeast 

 was infected with such species and used for pitching hopped 

 wort, these bacteria did not usually develop further. Although, 

 however, the bacteria did not develop during the fermentation, 

 a difference was often observable between the condition of 

 this beer and that of beer fermented with pure yeast. Acetic 

 acid bacteria were not infrequently found in the analyses, 

 and were usually able to assert themselves in the flasks, even 

 in competition with rival species. In a few cases the experi- 

 ments with wort showed a growth, and sometimes even an 

 abundant one, of Sarcina forms, which did not occur in the 



