Growth kinetics parameters and control of dissolved oxygen in a batch reactor during the aerobic growth of Kluyveromyces marxianus NRRLY-1196 yeast strain

This project aimed first at determining the growth kinetics parameters and a correlation for the oxygen transfer rate coefficient (kLa). Second at studying the need of adaptive control of dissolved oxygen (D.O.) in the culture medium to obtain a constant performance of the controlled system.;The microorganism selected for this work was Kluyveromyces marxianus NRRLY-1196, a yeast capable of metabolizing lactose, that produces the enzyme beta-galactosidase intracellularly under aerobic conditions. The enzyme production could be of great impact for those people who are not tolerant of lactose products.;Parameters such as maximum growth rate (0.624 h-1), solubility constant (0.208 g/L), and yield coefficient (Yx/s) (0.20--0.27 g biomass/g lactose) were estimated using shaken-flasks. The kLa (45.13 h-1-306.60 h-1) of the reactor and controller parameters for a stable D.O. response were determined using a 1.6-L bioreactor.;The adaptive control strategy to reach a constant performance of the controlled system was not necessary for K. marxianus. Under the operating conditions fixed in this process, the D.O. could be controlled satisfactorily using a simple PID controller with one value of Kc and agitation as the manipulated variable. A new parameter was defined based on the characteristics of the bioreactor and the microorganism to determine whether adaptive control was needed for the specified process.