FACTORS PRODUCING HIGH YEAST YIELDS IN SYNTHETIC MEDIA

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Abstract
By the use of adequate aeration and an improved synthetic medium, yields of Saccharomyces cerevisiae y-30 were obtained which were much greater than previously obtainable on synthetic media. A liter of medium containing 10 g. glucose, 2.5 g. asparagine, 6 g. (NH4) H2PO4, 0.2 g. KH2PO4, 0.25 g. MgSO4 -7H2O, 1 g. Na citrate (not fermented), 20 [mu]g. biotin, 0.5 mg. Ca pantothenate, 10 mg. inositol, 4 mg. thiamine, 1 mg. pyridoxine, 400 [mu]g. Zn, 150 [mu]g. Fe, and 25 [mu]g. Cu yielded 5.33 g. dry cells. Addition of small amts. of natural materials did not increase the yield. Of 21 amino acids tested, only alanine and serine could completely replace asparagine. The constituents were tested singly, and the above amts. were found more than adequate. On purified media, 75 [mu]g. Fe, 200 [mu]g. Zn, and 12 to 15 [mu]g. Cu per liter were adequate. Efficiency of aeration in shake flasks and a small fermenter was measured by the sulfite oxidation method. Opt. yields were obtained in both when about 1 millimole O2 was available per 1. per min. Higher levels of aeration decreased yields, the decrease not being due to loss of alcohol.
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