Carboxyl methyl cellulose (CMC) solutions with different concentrations simulating different mycelial fermentation broth were used for the study of mass transfer characteristics in bioreactor. Two impeller combinations (triple Rushton turbines

3PY and bottom hollow blade turbine combined with upper two up-pumping hydrofoils (3 blades)

HY+2KCXu) were employed. Under low CMC concentration condition

impeller combination of HY+2KCXu showed better mass transfer capacity. Fermentation of Aspergillus niger with production of glucoamylase was conducted under the two impeller combinations. In order to keep the similar oxygen uptake rate (OUR) among the two combinations

impeller rotation speed of the two configurations was adjusted respectively. Ultimately

based on the investigation of enzyme production

biomass amount

broth rheology and also mass transfer capacity of impellers

conclusions were gotten:apparent viscosity of broth in fermentation with HY+2KCXu was lower than that with 3PY. It seemed that in fermenter equipped with HY+2KCXu pellet prevailed than mycelia

thus lower viscosity was resulted

which in turn increased the mass transfer capacity of the system

that may be the reason why this impeller combination can gave higher product titer.