FACTORS INFLUENCING THE GROWTH OF MICROCYSTIS AERUGINOSA KÜTZ. EMEND. ELENKIN

Abstract

Yields of unialgal M. aeruginosa NRC-1 were increased from 685 mg dry wt./liter in 20 days to 1500 mg dry wt./liter in 7 days by increasing the concentrations of NaNO 3, K 2 HPO 4, and MgSO 4 in the medium of Fitzgerald et al. Within the concentration range that was favorable for growth the balance between these three salts was not especially critical. A low potassium tolerance was noted that appears to depend on the ratio of sodium to potassium in the medium. With the media used, growth was not limited by deficiencies of minor elements, iron, chelation, or any of 10 different vitamins, but was promoted by soil extract. The optimum temperature was approximately 28 °C; the optimum pH range was between 8 and 11. Vigorous aeration and agitation promoted growth by insuring better gas exchange and more efficient utilization of light and also, perhaps, by helping to relieve an inhibition caused by continuous leakage and/or lysis of the algal cells. Lysis was promoted by an excess of sodium (or deficiency of calcium) plus other unknown factors. Rapid growth with reasonably high yields was obtained under conditions which are suitable for large-scale culture operations.