kLa required to maintain critical oxygen concentration A genetically engineered strain of yeast is cultured in a bioreactor at 30C for production of heterologous protein. The oxygen requirement is 80 mmol l21 h21 ; the critical oxygen concentration is 0.004 mM. The solubility of oxygen in the fermentation broth is estimated to be 10% lower than in water due to solute effects. (a) What is the minimum mass transfer coefficient necessary to sustain this culture with dissolved oxygen levels above critical if the reactor is sparged with air at approximately 1 atm pressure