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Effects of Cation Levels of the Nutrient Medium on the Biochemistry of Chlorella

II. Factorial Experiment ¹

^a Department of Botany, University of Maryland, College Park, Maryland 20742

A factorial experiment was designed to study the effects of Mg²⁺, K⁺, and Na⁺ on the growth and biochemistry of Chlorella sorokiniana. Raising Mg²⁺ or K⁺ concentration in the nutrient medium increased growth rates as well as total N levels and Mg²⁺ and K⁺ accumulation by the cells. The total N effect was Mg²⁺-dependent—if Mg²⁺ was below a certain level in the medium—increasing the K⁺ concentration did not raise the total N level of cells. Low nutrient levels of K⁺ decreased the levels of unsaturated fatty acids (especially 18:1 and 18:3), while increasing the levels of palmitic acid (16:0), total fatty acids, and total lipid. Increasing nutrient K⁺ concentrations were accompanied by increases in levels of some unsaturated fatty acids, with a concomitant reduction in 16:0, total fatty acids and total lipid. Low Mg²⁺ levels in the nutrient medium reduced the cellular levels of palmitic acid, total fatty acids, total lipid, and certain unsaturated fatty acids (though this last effect also depended on the nutrient level of K⁺). These relationships indicate that Mg²⁺ may be important in the initial steps of fatty acid synthesis, whereas K⁺ may be necessary for the formation of certain unsaturated fatty acids. Variations in Na⁺ concentration did not have any significant effect on the growth and biochemistry of C. sorokiniana.