Abstract
Oxygen transfer to and within fungal pellet is discussed on the assumption that oxygen is supplied to the pellet interior by simple molecular diffusion. The assumption was found to be invalid under some operational conditions; the oxygen uptake rate for pellets of Aspergillus niger, measured in an agitated vessel, depended on operating conditions. Diffusional resistance around the pellet was negligible and the mass transfer rate within the pellet under ordinary agitation was enhanced from the rate by molecular diffusion. Estimated values of effective diffusivity within the pellet were more than twice the molecular diffusivity of oxygen. The oxygen uptake rate could be correlated with pellet diameter, agitation speed, impeller diameter and liquid viscosity.
