GROWTH AND METABOLISM OF ASPERGILLUS NIDULANS EIDAM IN SURFACE CULTURE

Abstract

Aspergillus nidulans was grown on glucose, fructose, sucrose, or maltose in a high-sugar medium favorable for fat formation. Glucose was more readily metabolized than the other sugars, giving a heavy felt with the highest fat content in a shorter time. Sucrose was inverted before absorption and was more conducive to growth than to fat formation. Maltose was probably absorbed after hydrolysis. It gave a heavy felt and a high fat yield but after a longer period of incubation than with glucose. Maltose metabolism was marked by lower nitrogen utilization. Hence, the maltose-fed mycelial felts had the highest carbohydrate content and the lowest protein content.Growth proceeded as long as there was available sugar in the culture medium. Extracellular nitrogenous compounds appeared in the culture media before the complete exhaustion of the sugar in some cases, providing evidence that this process is not purely autolytic in nature. The early growth phase on the different sugars was characterized by low-fat, high-protein mycelial felts. Active fat formation was found to start after the drop of the nitrogen content of the medium to a very low level. The inverse relationship between fat and protein contents in the mycelium was traced during growth on glucose, sucrose, or maltose at different stages of growth. On fructose, except for the early growth period, fat and protein syntheses proceeded proportionally.