A kinetic study of the growth of Aspergillus nidulans and other fungi.

The growth kinetics of Aspergillus nidulans, Mucor hiemalis and Penicillium chrysogenum on solid media and in submerged culture were studied. Growth of A. nidulans colonies on solid medium can be divided into the four phases of lag, exponential, deceleration and constant growth rate. The growth kinetics of A. nidulans in submerged culture were similar to those commonly found for unicellular micro-organisms. The effects on colony radial growth rate, of glucose concentration, medium depth, oxygen partial pressure and temperature were studied. The radial growth rate of glucose-limited colonies of A. nidulans increased linearly with the log. of the initial glucose concentration. The effects of glucose concentration on internode length, hyphal density and hyphal diameter were also studied. At glucose concentrations above I % (wlv) there was an inverse relation between the radial growth rate of A. nidulans colonies and their peripheral hyphal density. The relations between colony radial growth rate (K,) and germ tube specific growth rate (ag) on solid media and specific growth rate in submerged culture (a,) were investigated. Direct proportionality between K, and a, of A. niduZans was found by varying specific growth rate by temperature changes. The germ tubes of A. nidulans conidia grew exponentially at a rate which was about 2.3 times as great as the specific growth rate of the organism in submerged culture. The colony radial growth rates of the three moulds could not be used as a measure of their relative specific growth rates in submerged culture.