Comparison of experimental methods for determination of the volumetric mass transfer coefficient in fermentation processes

Mass transfer in bioreactors has been examined. In the present work, dynami c methods are used for the determination of K(L)a values for water, model m edia and a fermentation broth (Candida utilis) in an airlift reactor. The c onventional dynamic method is applied at the end of the microbial process i n order to avoid an alteration in the metabolism of the microorganisms. New dynamic methods are used to determine K(L)a in an airlift reactor during t he microbial growth of Candida utilis on glucose. One of the methods is bas ed on the continuous measurement of carbon dioxide production while the oth er method is based on the relationship between the oxygen transfer and biom ass growth rates. These methods of determining K(L)a does not interfere wit h the microorganisms action. A theoretical mass transfer model has been use d for K(L)a estimation for the systems described above. Some differences be tween calculated and measured values are found for fermentation processes d ue to the model is developed for two-phase air-water systems. Nevertheless, the average deviation between the predicted values and those obtained from the relationship between oxygen transfer and biomass production rates are lower than 25% in any case.