Lipid Formation in Cryptococcus terricolus. II. The Effect of Ion Variation on Growth and Lipid Formation.

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Abstract
The following medium was found satisfactory for maximum growth and lipid production in C. terricolus: glucose 40.0 g, urea 0.6 g, KH2PO4 0.5 g, MgSO4.7H2O 1.0 g, Fe(III)-citrate.3H2O 0.1 g, 0.2 mg of Zn as ZnSO4.7H2O, 0.001 mg of Cu as CuSO4.5H20, and 0.001 mg of Mn as MnCl2.4H2O to one liter of redistilled water. Finally, 50 mg of ethylenediamine tetraacetic acid (EDTA) was added per liter. This medium permits the production of approximately 34.5 g of yeast dry matter containing 21 g of lipids/100 g of assimilated glucose. This yield has been found to remain constant during a large number of transfers in the same medium. The following ions have to be added to the medium in order to obtain maximum growth: K, Mg, phosphate, sulphate, Fe, Zn, and Cu. Supraoptimum doses of K, Zn, and Cu had a markedly inhibiting effect on the growth of the organism. Addition of Na, Ca, Mn, Mo, Co, and Cl seemed to have no effect on the growth. The lipid content of the cells was influenced by variations in the different elements in the same manner as the growth. However, contrary to the results obtained in the absence of the other ions, a lack of phosphate or sulphate led to an increased lipid content in the cells. This lipid production may perhaps be compared with the degenerative lipid production found with aging in different organisms. More phosphate and Mg were required in the medium for producing maximum lipid content, than for producing a maximum amount of yeast dry matter. Mn, introduced into the medium in a concentration of 0.001 ppm, or more, increased the lipid content of the cells. The other elements, which did not affect the growth, had no effect on the lipid content either. The lipid coefficient generally followed the variations in the lipid content. With increasing Mg supply, however, it looked as if the effectiveness of the conversion of glucose into lipids decreased. The protein content of the yeast was found to be fairly constant, viz. 10-15% of the dry weight.