Estimation of steady-state culture characteristics during acceleration-stats with yeasts

Steady-state culture characteristics are usually determined in chemostat cu ltivations, which are very time-consuming. In contrast, acceleration-stat ( A-stat) cultivations in which the dilution rate is continuously changed wit h a constant acceleration rate are not so time-consuming, especially at hig h acceleration rates. Therefore, the A-stat could be advantageous to use in stead of the chemostat. However, the highest acceleration rate, meaning the fastest A-stat that can be applied for estimating steady-state culture cha racteristics, is not known yet. Experimental results obtained with Zygosacc haromyces rouxii, an important yeast in soy sauce processes, showed that th e culture characteristics during the A-stat with an acceleration rate of 0. 001 h(-2) were roughly comparable to those of the chemostat. For higher acc eleration rates the deviation between the culture characteristics in the A- stat and those in the chemostat obtained at the same dilution rate generall y started to increase, The source of these deviations was examined by simul ation for Saccharomyces cerevisiae, The simulations demonstrated that this deviation was not only dependent on the metabolic adaptation rate of the ye ast, but also on the rate of change in environmental substrate concentratio ns during A-stats. From this work, it was concluded that an A-stat with an acceleration rate of 0.001 h(-2) is attractive to be used instead of chemos tat whenever a rough estimation of steady-state culture characteristics is acceptable. (C) 2001 John Wiley & Sons, Inc.