Substrate effects in tower loop reactors

Summary Hansenula polymorpha was cultivated in a bubble column loop bioreactor employing ethanol and/or glucose as substrates. By varying the substrate concentration, the cultivations were carried out in non-limited, substrate limited and oxygen transfer limited growth ranges. The influence of the transitions from one range to another on reactor performance (OTR,k _L a, a) and cell productivity () were investigated. When employing ethanol as a substrate, the concentration considerably influences the fluid dynamics, mass transfer phenomena and cell productivity. When employing glucose as a substrate, glucose repression occurs. At high glucose concentrations no transition into the oxygen transfer limited growth is possible. The ethanol produced during the glucose repression influences the fluid dynamics, mass transfer phenomena and productivity. With decreasing glucose concentration the glucose repression can be gradually eliminated.