While some ale yeast strains are able to flocculate when cultured in a defined medium of glucose, ammonium salts, vitamins and ions, others require the presence of a nitrogen-containing inducer in the growth medium. On the other hand, all flocculent lager strains examined to date are able to flocculate after being cultured in a defined medium and do not appear to require the addition of inducer material to the growth medium. The inducer material present in wort has been identified as peptide. By the use of ion exchange chromatography the peptide fraction that induces flocculation has been found to contain a high level of acidic amino acid residues with a very similar structure to that reported for the a-factor involved in sexual agglutination of haploid a. and a cells of Sacch. cerevisiae.Studies on the adsorption of Ca++ ion by the cell wall failed to reveal any significant differences in total uptake between flocculent and non-flocculent cultures. It would appear that Ca++ ions are bound less tightly by non-flocculent cells than by flocculent cells. The contribution of calcium to flocculation is not the absolute amount of this ion adsorbed by the yeast cell wall but rather the stereo-specific manner by which it is bound, i.e., its position relative to the three-dimensional structure of the yeast cell wall.

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The rate of spheroplast formation in stationary phase cells of Socc/ioromyces eerev/s/ae has been found to be increased as a result of pre-treatment of the cells with protease. The protease has been found selectively to remove the cell wall's mannanphosphate-protein layer and thus greatly facilitate the action of snail gut enzymes or other such enzymes, in their hydrolytic activity upon the glucan of the cell wall.

The goal of the present investigation was to study the influence of various brewing parameters on the total lipid content as well as the fatty acid composition of the yeast. The effects of fermentation temperature, aerobic vs. anaerobic growth, yeast strain, and adjunct level were explored. The results revealed that yeast contained more lipids and more unsaturated fatty acids when grown at lower temperatures. Aerobic growth conditions increased the amount of unsaturated acids and sterols. The fatty acid composition of three yeast strains displayed some differences when grown under identical conditions and the total lipid content rose markedly when increasing portions of corn syrup were used for wort production. In an effort to determine the site of these lipid changes, yeast cells were homogenized and subjected to a differential centrifugation. Three different subcellular particles were obtained and analyzed for lipids. An attempt was made to correlate some of these findings with the accumulation of ethyl acetate in the resultant beer.