Agitation induced mycelial fragmentation of Aspergillus oryzae and Penicillium chrysogenum

Given the impact of mycelial morphology on fermentation performance, it is important to understand the factors that influence it, including agitation-induced fragmentation. The successful application of the energy dissipation/circulation function (EDC) to correlate fragmentation of Penicillium chrysogenum with agitation intensity and with different impeller types [5] has already been demonstrated. The EDC function takes into account the specific energy dissipation rate in the impeller swept volume and the frequency of mycelial circulation through that volume. In order to explore whether the EDC function can be used more generally to correlate fragmentation of different filamentous species, the present study extended the concept to agitation-induced, off-line fragmentation of Aspergillus oryzae grown in chemostat culture. The work shows that at EDC values off-line greater than that in the chemostat, fragmentation with different impellers can be correlated with the EDC. For EDC values less than those used in the chemostat, fragmentation did not occur. The earlier results of Justen et al. [5] with Penicillium chrysogenum are also reconsidered and found to behave similarly. (C) 2000 Elsevier Science S.A. All rights reserved.