VIEW ARTICLE    DOI: 10.1094/ASBCJ-45-0135

A New Medium for the Detection of Wild Yeast in Brewing Culture Yeast. J. De Angelo and K. J. Siebert, The Stroh Brewery Co., Detroit, MI 48207. J. Am. Soc. Brew. Chem. 45:0135, 1987.

The growth characteristics of 469 different yeast species listed in "The Yeasts: Characteristics and Identification" by Barnett, Payne, and Yarrow (1983) were entered into a microcomputer data base management program. This system was used to find combinations of carbon sources that would support the growth of as many yeast species as possible, but which would not support the growth of brewing culture yeast. According to the theoretical analysis carried out, a combination of five carbon sources (xylose, mannitol, adonitol, cellobiose, and sorbitol) should permit growth of 394, or 84%, of the known yeast species. A medium containing a combination of the five carbon sources, designated XMACS, was prepared and used for examination of known wild yeast strains and production yeast samples. Forty-one pure yeast cultures were plated on a number of media. Of 23 non-Saccharomyces cerevisiae strains, 14 each grew on XMACS or lysine medium or during incubation at 37° C; five grew on cycloheximide medium, and copper sulfate medium supported the growth of 21 of the organisms tested. None of the 18 Saccharomyces cerevisiae strains tested grew on cycloheximide or lysine media; 10 grew on XMACS, 11 at 37° C, and 12 on copper sulfate medium. Over a period of time, 76 samples of plant pitching yeast were examined with five media. Wild yeasts were detected in 15 samples with XMACS; this was significantly higher than the two positive results found with cycloheximide or the six found with lysine or copper sulfate media. Growth at 37° C resulted in 13 positive results, which was similar in effectiveness to XMACS.

Keywords: Data base, Media, Cycloheximide, Copper, Lysine, XMACS