Selection of Saccharomyces pastorianus variants with improved fermentation performance under very high gravity wort conditions

Saccharomyces pastorianus FBY0095 was mutated and variants were selected for efficient very high gravity brewing using 15% (w/v) maltose and 15% (w/v) ethanol. Two useful variants were obtained of which one (L6) had growth, wort consumption and ethanol production rates of 0.036, 1.13 and 0.49 g l(-1) h(-1), respectively. The corresponding results for the wild type were 0.028, 0.98 and 0.4 g l(-1) h(-1), respectively. The vitality of the variant (expressed as acidification power) was 2.5 while that of the wild type was 2.3. There was also an obvious improvement on flavor of resulting beer when using L6 and the other variant.