Design and evalution of control strategies for high cell density fermentations

Abstract

A methodology for the design and evaluation of bioprocess control strategies is presented. The strategies manage nutrient supply with demand and vary with the metabolic condition and phase of fermentation operation. Six carbon source addition strategies are based on different combinations of available measurements; they are described and evaluated under different operating conditions for yeast cultivation. It is concluded that a single control strategy is not the most appropriate under all possible operating conditions. An oxygen uptake rate-based control strategy performs better with a mean respiratory quotient (RQ) value less than 1.1 during an oxygen limitation than an ethanol control strategy which had a mean RQ of 14. The designed strategies and an approach of applying the strategy that best matches fermentation conditions consistently enables achievement of high cell densities 78.7 g DCW/L and yields 0.50 g DCW/g glucose as the mean values for three fermentations.

The A1 · U72 Base Pair Conserved in Eukaryotic Initiator tRNAs Is Important Specifically for Binding to the Eukaryotic Translation Initiation Factor eIF2

“…(i) Growth of cells. Medium (10 liters) for fed-batch fermentation of S. cerevisiae was the one used by O'Connor et al (34). The fermentor was inoculated with a 1-liter culture of late-log-phase yeast cells grown in synthetic medium (SD ϩ Ura, Trp, and His).…”

High Yield Production of Heterologous Proteins with Escherichia coli

“…To increase product yields and to ensure consistent product quality key issues of industrial fermentations process optimisation and scale-up are aimed at maintaining optimum and homogenous reaction conditions, minimising microbial stress exposure, and enhancing metabolic accuracy 44,76 . Cells close to the injection port are exposed to high concentrations of nutrients, whereas at other locations, cells are starved of substrate 4,70 .…”

Comparative evaluation of various control schemes for fed-batch fermentation

“…In single optimal control strategy, the feed rate is adjusted by means of an optimal pro®le determined either of¯ine (programmed control approach) or online (feedforward control approach). The determination of this optimal feed rate pro®le can be carried out by using the simpli®ed material balance equations and optimization procedures [1,2,3,4]. In single feedback control strategy, the regulation of the feed rate relies merely on the feedback control scheme.…”