Studies on yeast metabolism. 5. The trehalose content of baker's yeast during anaerobic fermentation

In a previous study of the synthesis of cellular carbohydrate during fermentation by D.C.L. baker's yeast (Trevelyan, Gammon, Wiggins & Harrison, 1952) little variation was found in the trichloroacetic acid-soluble carbohydrate, of which the main constituent is trehalose (Trevelyan & Harrison, 1952).The low concentration of glucose in the medium used, about 5 mm, was thought to have restricted trehalose synthesis.The present paper reports measurements of trehalose in yeast during fermentation of high concentrations of sugar.As Brandt (1941) reported that trehalose disappeared rapidly from the yeast cell as a result of growth in a suitable medium, but increased in amount during metabolism in the absence of assimilable nitrogen, particular attention has been paid to the effect on yeast trehalose of nitrogenous constituents of the medium.Disappearance of trehalose during budding has been noted also by Pollock & Holmstrom (1951).Recently a study of some aspects of the connexion between carbo- hydrate and nitrogen assimilation in TorulOp8i8 utilie has been published by Yemm & Folkes (1954). METHODSFermentation was carried out at 30°, using, unless otherwise stated, a suspension of 2B5 g. (wet wt.) of pressed D.C.L. baker's yeast/80 ml.This was stirred by a stream of 150 ml. of N2/min.Four separate batches of yeast (referred to below as yeast I, II, III or IV) were used in the investigation; one (yeast IV) had a much higher trehalose content than the rest.Fermentation was initiated by adding 20 ml. of sugar solution.After allowing 2 min.for mixing, the first sample was withdrawn for carbohydrate determina- tion.Media.The 'full medium' contained 0*05M sodium succinate buffer, pH 5*5, 2 mM-KH2PO4, 8 mM-KCI, 5 mM-MgSO4, 0.01M-(NH4)2S04I 0-02M DL-asparagine and 5,UM thiamine.The 'N-free medium' had no ammonium salts or asparagine.The 'P-free medium' contained 001 M- KCI, but no KH2P04.The 'asparagine-free medium' had 0-05M-NH4Cl as sole nitrogen source.The fermentable sugars used were glucose, fructose or mannose, in an initial concentration of 0 3 M (unless stated otherwise) and sucrose or maltose, 0 15M.In the most rapid fermentation the * Part 4: Trevelyan & Harrison (1954b).