Influence of oxygen and medium conditions on the performance of a tower reactor with an external loop

Hansenula polymorpha was cultivated using ethanol and/or glucose as substrate in a bubble column, air lift, loop reactor. The optimum aeration rate was determined for extended culture operation. Considerable influence of the ethanol concentration on the volumetric mass transfer coefficient (kLa), and the specific gas-liquid inter-facial area (a) was found. Glucose concentration had no comparable influence on kLa and a. The influence of lack of substrate and/or dissolved oxygen on the culture was investigated. For 30 min the absence of substrate did not influence μm, whereas a lack of dissolved oxygen for 2.5 min reduced μm to one half of its original value.