Concentration effects of main components of synthetic culture media on oxygen transfer in bubble column bioreactors

Abstract

The effects of the concentration of three kinds of constituents of aqueous culture media (mixed electrolytes, glucose, sucrose, and commercial antifoam) on oxygen transfer were studied in a bubble column bioreactor. The volumetric mass transfer coefficient (kLa) and the specific interfacial area (a) were measured at five superficial gas velocities under the homogeneous bubbling regime. The mixed electrolytic salts (0 ≤ ionic strength ≤ 0.4126 M) and, to a lesser extent, the glucose (0 ≤ c ≤ 0.222 M) caused the increase of kLa up to a maximum value, followed by a either a slight decrease, or no significant change. The higher values of kLa corresponded to critical concentrations, indicating a maximum inhibition of bubble coalescence. The kLa was governed by changes in interfacial area up to the critical concentrations, where the dominant contribution shifted to kL; at the studied concentrations, the sucrose had no significant effect on kLa. Finally, low concentrations of commercial antifoam caused an overall decrement in kLa due entirely to the hindering effects of antifoams on kL.