Hydrodynamic characteristics and mixing behaviour of Sclerotium glucanicumculture fluids in an airlift reactor with an internal loop used for scleroglucan production

The filamentous fungus, Sclerotium glucanicum NRRL 3006, was cultivated in a 0.008 m(3) airlift bioreactor with internal recirculation loop (ARL-IL) f or production of the biopolymer, scleroglucan. The rheological behaviour of the culture fluid was characterised by measurement of the fluid consistenc y coefficient (K) and the flow behaviour index (n). Based on these measurem ents, the culture fluid changed from a low viscosity Newtonian system early in the process, to a viscous non-Newtonian (pseudoplastic) system. In addi tion, reactor hydrodynamics and mixing behaviour were characterised by meas urement of whole mean gas hold-up (epsilon (g)), liquid re-circulation velo city (U-ld) and mixing time (t(m)). Under identical process conditions, the effects of the viscosity of the culture fluid and airflow rate on epsilon (g), U-ld and t(m) were examined and empirical correlations for epsilon (g) , U-ld and t(m) with both superficial velocity U-g and consistency coeffici ent K were obtained and expressed separately. The correlations obtained are likely to describe the behaviour of real fungal culture fluids more accura tely than previous correlations based on Newtonian or simulated non-Newtoni an systems.