A strain of Aspergillus fumigatus was grown on ten nutrient media containing glucose and various (organic and inorganic) sources of nitrogen. Growth of the mycelia, pH of the cultivation fluid, uptake of nutrients and proteolytic activity on haemoglobin at pH 3 and on azocasein at pH 7.5 were assessed. The aim of the study was to find the physiological conditions for the production of extracellular proteases. High activities of alkaline protease(s) were found only when the following three conditions were fulfilled: (a) exhaustion of glucosefrom the medium, (b) reaching of the maximum mycelium dry weight, (c) rise of the medium pH to at least 7. These three factors are causally related and coincide in time so that they can hardly be evaluated individually. A neutral to alkaline pH is certainly a necessary condition and a steep rise in pH may itself be a sufficient triggering factor for the syn the sis of protease(s). The presence of proteins and/or peptides as inducers is probably not quite necessary but is never the less strongly stimulating. The activity of acid (aspartic) protease was small to negligible on all media and its production clearly depended only on the pH of the medium (optimum pH 4 to 6).
Kunert J. (1996): Growth and production of extracellular proteases by the fungus Aspergillus fumigatus on various media. I. Media without proteins. – Czech Mycology 49(2): 91–106.
