Slime Production by Brewery Strains of Pediococcus Cerevisiae. D. Van Oevelen and H. Verachtert, Laboratory of Industrial Microbiology and Biochemistry, University of Louvain, Kard. Mercierlaan 92, B-3030 Leuven, Belgium. J. Am. Soc. Brew. Chem. 37:0034, 1979.

By its formation of lactic acid and diacetyl, Pediococcus cerevisiae is essential in the production of lambic beer, a Belgian beer with an acid, vinous character. P. cerevisiae strains may, however, turn the beer to an oily fluid, a disorder that is known as ropiness. Microbial analysis of ropy and nonropy lambic samples shows simultaneous presence of three types of P. cerevisiae colonies, with a high proportion of slimy variants causing ropiness. Pure cultures of these tetrad-forming cocci grow best under reducing conditions and are stimulated by carbon dioxide. Glucose, maltose, fructose and saccharose produce slime, and well-buffered media produce higher viscosities. Stirring the cultures in the presence of air completely destroys the viscosity. Mixed culture experiments with P. cerevisiae and yeasts suggest that growing cells of Brettanomyces strains can hydrolyze the slime. Paper chromatographic analysis shows that hydrolysates of purified slime preparations are composed of carbohydrates, nucleic acids and proteins. Glucose, mannose and a small amount of ribose are the only sugars, and the nucleic acid is RNA.

Keywords: Lambic, Pediococcus cerevisiae, Ropiness, Slime