UPTAKE OF AMINO ACIDS IN BOTTOM FERMENTATIONS

The net uptake of amino acids in full-scale brewery fermentations with a strain of Saccharomyces carlsbergensis at 8–9° C. has been followed by analysing amino acids in fermenting wort and beer. The amino acids are usually taken up very incompletely and their uptake follows a certain order, not very different from that observed by British authors using top yeast fermenting at 15° C. The order is not quite constant, however; particularly the uptake of arginine and of ammonia are subject to variations. The amino acids can be divided, according to their rate of absorption and degree of utilization, into three clear-cut groups. The results suggest that it is the system allowing entry of amino acids into the cell that is of prime importance and that this is not capable of regulating the uptake to the demand of amino acids as building blocks for yeast protein. The results are considered in the light of recent investigations on amino acid permeases of yeast, and the metabolic roles of the most rapidly absorbed amino acids, serine, asparagine, glutamine, and threonine, are discussed.