NUTRITIONAL STUDIES ON THE GENUS HIRSUTELLA: I. GROWTH RESPONSE IN AN ENRICHED LIQUID MEDIUM

Abstract

Quantitative comparative studies on the growth of Hirsutella gigantea in shaken yeast extract – dextrose medium have shown that the rate of growth and total yield is affected by the quantity of inoculum. The highest yield is obtained with an inoculum level ranging from 0.2 to 0.4 mg/50 ml; moreover results from repeated experiments tend to be relatively uniform. With smaller quantities of inoculum, i.e. 0.1 mg or less, the uniformity of growth among replicates is affected. An increase in the amount of inoculum above the optimum, while accompanied by a higher rate of growth, results in a gradual decrease in the total yield.With approximately 0.2 mg of inoculum the maximum yield, 673.4 mg of fungal mycelium, was obtained after 12 days' incubation in a medium containing 1.5% yeast extract and 2% dextrose.The fungus does not grow in a basal dextrose–salts medium with potassium nitrate or ammonium nitrate as the nitrogen source. The effectiveness of yeast extract indicates a requirement for organic nitrogen. Yeast extract may also act as a source of growth factors.