A link between vacuolation and fragmentation of Penicillium chrysogenu
m mycelia in stirred tank submerged fermentations is reported. Quantit
ative information on vacuolation and morphology was obtained by image
analysis. In fed-batch fermentations the coincidence of the events of
rapid vacuolation and the fall of the mean total and main hyphal lengt
hs suggests that hyphal fragmentation is not necessarily due to ''shea
r'' alone. The physiological state of the hyphae, characterized by the
proportions of vacuoles, was found to have a significant influence on
the breakage of mycelial hyphae. It was found that the fragmentation
was greater when the hyphae became heavily vacuolated following nutrie
nt limitation in the culture, i.e., during the switch from the rapid g
rowth to the production phase. (C) 1994 John Wiley and Sons, Inc.