"Yoghurtbier, brewed in many areas of North and Central Germany, is not dissimilar in taste to Berliner Weissbier; it is made by souring the wort (of barley malt and wheat malt) with a pure culture of bacillus bulgaricus and fermenting the soured wort with a highly-attenuating top-fermenting yeast and contains living bacillus bulgaricus. As there is no requirement for it to appear clear, in fact on the contrary the cloudy look caused by the presence of large quatities of bacillus bulgaricus is desired, Yoghurtbier is ready for consumption a few days after being filled into bottles. as soon as there is sufficient CO2."
"Encyklopädisches Handbuch der technischen Chemie, Volume 4, Part 1", 1915, page 5. (My translation.)
Maybe some of you brewers could make a guess as to how this beer would taste. Sour, I suppose.