YEAST MUTANTS EXCRETING VITAMIN B1 AND THEIR USE IN THE PRODUCTION OF THIAMINE RICH BEERS*,†

In certain strains of Saccharomyces cerevisiae and Saccharomyces uvarum (carlsbergensis), high doses of ultraviolet radiation induced stable mutants excreting thiamine from their living cells during the ethanol production. In S. cerevisiae, the first mutagenesis step yielded mutants with the production of 0·3–0·5 mg extracellular thiamine. HCL/litre minimum medium without thiamine and the second one increased the production up to 2·0–2·1 mg thiamine. HCL/litre. In S. uvarum (carlsbergensis), mutants producing up to 0·76 mg thiamine. HCL/litre 10% Plato hopped wort were obtained in the first mutagenesis step combined with mitotic recombinations. The increase up to 0·92 mg/litre was achieved here by repeated selections. Both laboratory and pilot plant fermentations in 10 and 4% Plato hopped worts showed the suitability of selected mutants for the production of thiamine rich beers which fulfilled all quality requirements and contained 0·67–0·80 and 0·22–0·33 mg thiamine. HCI/litre, respectively.