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

The influence of Paecilomyces japonica pellet morphology on fermentation br oth rheology and exo-biopolymer production was investigated in a 5-l jar fe rmenter. Rapid formation of pellets was observed after the first day of fer mentation; and these slowly increased in size and roughness. This, together with the increase in biomass concentration, altered the transport characte ristics and broth rheology towards a pseudoplastic nature which, in turn, i nfluenced cell growth and exo-biopolymer production. At mild agitation high aeration and optimum substrate concentration, pellets were the most predom inant morphological form, compared with free mycelia. The broth rheology sh owed pseudoplastic behavior; and the fungal morphology was closely related to the rheological properties.