The influence of geometry on hydrodynamic and mass transfer characteristics in an external airlift reactor for the cultivation of filamentous fungi

The influences of geometric configuration, mycelial broth rheology and supe rficial gas velocity (U-sg) were investigated with respect to the following hydrodynamic parameters: gas holdup (epsilon), oxygen transfer coefficient (K(L)a) and mixing time (t(m)). Increases in U-sg and height of gas separa tor (H-t) caused an increase in epsilon and K(L)a, and a decrease in t(m). Consequently, a diameter ratio (D-d/D-r) of 0.71 and H-t 0.20 m were found to be the best geometry and operation parameters to achieve high aeration a nd mixing efficiency for the high viscous broth system in the cultivation o f filamentous fungi. An external airlift reactor (EALR) was developed and d esigned for the cultivation of filamentous fungi. The EALR with two sparger s excels in reliability and high aeration and mass transfer coefficiency, r esulting in a fast mycelial growth and high biomass productivity in the cul tivation of the fungus Rhizopus oryzae.