Transient growth- and product-formation kinetics of acetic acid bacteria

Rates of growth and product formation under non-stationary conditions were measured in fermentations of industrial acetic acid bacteria. A repeated-batch process, where conditions change rapidly, and a slower shift experiment in CSTR culture were examined. Significant deviations from the steady-state kinetics determined in continuous fermentations were found for cell growth as well as for the formation of acetic acid. Algebraic functions of the inhibiting acid concentration were identified to describe the rates of reaction under stationary conditions. Transient kinetics are modeled by phenomenological differential equations. The data from both the repeated-batch experiments and the CSTR shift is consistently reproduced. Measurements and simulation results are presented in phase diagrams of the reaction rates over the concentration of acetic acid. Due to the dynamic effects, which enhance the transient rates of both growth and product formation, the repeated-batch process is superior to a continuous fermentation in terms of total volumetric productivity and final acid concentration.