 Two unique strains of yeast were traditionally used ; one highly flocculent strain that was responsible for most of the fermentation in the first few days , and the other , a powdery and less flocculant strain , that was slower and finished off the beer in the fermentation vats and in the bottles . Until the end of the 19th century , the breweries that produced Grodziskie used a single strain of yeast that was characterized by low attenuation and early flocculation . However , that strain was lost in the early 20th century . After World War II , yeast was imported from the <unk> Brewery in Berlin . That yeast was not well suited for producing Grodziskie and was frequently contaminated with spoilage organisms including Lactobacillus . In the 1960s , the state @-@ owned brewery was able to isolate and maintain its own varieties of yeast and yeast bank , but only the highly @-@ flocculant strain has been preserved to this day . Without access to the actual yeast used historically , most modern recreations of Grodziskie typically use ale yeasts that do not contribute a significant amount of yeast character to the beer . 
