Feedback control based on NADH fluorescence intensity for Saccharomyces cerevisiae cultivations

Abstract

Abstract Background A glucose concentration is an important factor for a fed-batch process of Saccharomyces cerevisiae. Therefore, it is necessary to be controlled under a critical concentration to avoid overflow metabolism and to gain high productivity of biomass. In the study, 2D fluorescence spectroscopy was applied for an online monitoring and controlling of the yeast cultivations to attain the pure oxidative metabolism. Results The characteristic of the NADH intensity can effectively identify the metabolic switch between oxidative and oxidoreductive states. Consequently, the feed rate was regulated using the single signal based on the fluorescence intensity of NADH. With this closed-loop control of the glucose concentration, a biomass yield was obtained at 0.5 g biomass/g glucose. In addition, ethanol production could be avoided during the controlled feeding phase. Conclusions The fluorescence sensor with a single signal of the NADH fluorescence intensity has potential to control a glucose concentration under the critical value in real time. Therefore, this achievement of the feedback control is promising to build up a compact and economical fluorescence sensor with the specific wavelength using light-emitting diodes and photodiodes. The sensor could be advantageous to the bioprocess monitoring because of a cost-effective and miniaturized device for routine analysis.

Keywords

• Bioprocess monitoring
• Fluorescence spectroscopy
• Closed-loop control
• Saccharomyces cerevisiae
• NADH