Amino Acid Utilization During Twelve Consecutive Industrial Repitching Cycles of Saccharomyces pastorianus in Lager Beer Fermentation

Amino acids are key assimilable nitrogen sources for brewing yeast and important precursors of beer flavor compounds. This study investigated amino acid utilization during 12 consecutive industrial lager fermentations with Saccharomyces pastorianus under serial repitching conditions. Samples were collected throughout fermentation and analyzed by HPLC. Fermentation performance remained comparatively stable across all repitching cycles, with little variation in final alcohol content, real degree of fermentation, apparent extract, and pH. Later cycles reached comparable terminal states approximately one day earlier. Exploratory principal component analysis showed that PC1 accounted for 75.29% of total amino-acid-profile variance and primarily reflected the progression of samples from early to later fermentation stages; principal components were not assigned directly to experimental factors. Terminal-value regressions identified the strongest cycle-associated trend for aspartate (nominal p < 0.001; adjusted R2 = 0.71), which remained statistically supported after false-discovery-rate correction. Nominal trends observed for asparagine and serine did not remain significant after correction for multiple testing. Overall, conventional fermentation performance and the global structure of amino acid utilization remained comparatively stable across the twelve-cycle industrial sequence. Because the experiment comprised a single consecutive repitching sequence rather than independently replicated generations, cycle-associated changes should be regarded as exploratory process-level observations.