EXPERIMENTAL PULSE TECHNIQUE FOR THE STUDY OF MICROBIAL KINETICS IN CONTINUOUS-CULTURE

A novel technique was developed for studying the growth kinetics of mi croorganisms in continuous culture. The method is based on following s mall perturbations of a chemostat culture by on-line measurement of th e dynamic response in oxygen consumption rates. A mathematical model, incorporating microbial kinetics and mass transfer between gas and liq uid phases, was applied to interpret the data. Facilitating the use of very small disturbances, the technique is non-disruptive as well as f ast and accurate. The technique was used to study the growth kinetics of two cultures, Methylosinus trichosporium OB3b growing on methane, b oth in the presence and in the absence of copper, and Burkholderia (Ps eudomonas) cepacia G4 growing on phenol. Using headspace flushes, gas blocks and liquid substrate pulse experiments, estimates for limiting substrate concentrations, maximum conversion rates V-max and half satu ration constants K-s could rapidly be obtained. For M. trichosporium O B3b it was found that it had a far higher affinity for methane when pa rticulate methane monooxygenase (pMMO) was expressed than when the sol uble form (sMMO) was expressed under copper limitation. While for B. c epacia G4 the oxygen consumption pattern during a phenol pulse in the chemostat indicated that phenol was transiently converted to an interm ediate (4-hydroxy-2-oxovalerate), so that initially less oxygen was us ed per mole of phenol. (C) 1998 Elsevier Science B.V. All rights reser ved.