Changes in morphology of Paecilomyces japonica and their effect on broth rheology during production of exo-biopolymers

The influence of Paecilomyces japonicapellet morphology on fermentation broth rheology and exo- biopolymer production was investigated in a 5-l jar fer- menter. Rapid formation of pellets was observed after the first day of fermentation; and these slowly increased in size and roughness. This, together with the increase in biomass concentration, altered the transport characteris- tics and broth rheology towards a pseudoplastic nature which, in turn, influenced cell growth and exo-biopoly- mer production. At mild agitation, high aeration and op- timum substrate concentration, pellets were the most pre- dominant morphological form, compared with free mycelia. The broth rheology showed pseudoplastic be- havior; and the fungal morphology was closely related to the rheological properties.