ABSTRACT
In submerged culture the morphology of filamentous micro-organisms varies between pellets and free filaments depending on culture conditions and the genotype of the strain. All the growth forms have their own characteristics concerning growth kinetics, nutrient consumption and broth rheology. Of the two extremes, pellet suspensions exhibit Newtonian rheological behaviour, while the filamentous form produces more viscous media with consequent effects of poor mixing and mass transfer. This is unfortunate, as it is very often the case that the disperse filamentous form is the productive form. Another drawback with the pelleted suspension is that cell growth occurs only at the surface of the pellets where contact with oxygen and other nutrients is adequate, and the cells growing within a pellet respond to a very different environment. Further into the pellet, mass transfer limitation will gradually occur and cells could autolyse.
