Inorganic micronutrient requirements of Chlorella. II. Quantitative requirements for iron, manganese, and zinc

Abstract

The quantitative inorganic micronutrient requirements of Chlorella pyrenoidosa for iron, manganese, and zinc were determined by obtaining plots of yield versus amount of added micronutrient in media devoid of added chelating agents. It is estimated that for growth of 1 g. of dried Chlorella, there is required a minimum of approximately 30 μg. iron, 2.5 μg. manganese, and 4.5 μg. zinc under the experimental conditions employed. In the presence of ethylenediaminetetraacetic acid (EDTA), much larger quantities of all required micronutrients must be supplied for a defined yield, with the sole exception of iron; the iron requirement is the same in the presence or absence of EDTA. In the absence of EDTA, iron added in the form of potassium ferricyanide was up to twice as effective for growth per unit of iron as was iron as ferrous sulfate; this advantage was most marked in alkaline solutions. Both iron sources were equally effective in the presence of EDTA.