CHANGES IN THE CARBOHYDRATE RESERVES OF BAKER'S YEAST DURING GROWTH AND ON STANDING

Abstract

During the propagation of baker's yeast, its carbohydrate composition changes markedly during transfer from anaerobic to aerobic conditions. The total carbohydrate content, determined by the anthrone method and expressed as glucose, increases from about 22% to almost 40%. The contents of glycogen and especially trehaiose, increase stage by stage, the commercial yeast containing 8-5% of trehaiose and about 12% of glycogen. The trehaiose disappears almost completely and the glycogen partly during the first hour of each growth stage but is finally resynthesized. Of the carbohydrates present, trehaiose and glycogen are metabolically the most active, and changes in their contents show great similarity. The mannan content of the yeast doubles when aeration is increased and remains at a high level during the final growth. Mannan is quantitatively the principal carbohydrate, the commercial baker's yeast containing about 17%. A high carbohydrate content increases the resistance of baker's yeast to autolysis. On standing, trehaiose and glycogen are mobilized, while the mannan remains intact. The polyphosphates do not seem to constitute an energy reserve of the cells; on the contrary, a high content of poly phosphates rather tends to reduce stability.