2-DIMENSIONAL FLUORESCENCE SPECTROSCOPY - A NEW TOOL FOR ONLINE BIOPROCESS MONITORING

Two-dimensional fluorescence spectroscopy is presented as a new method for bioprocess monitoring. It covers a wide range of excitation and e mission wavelengths and is a further development of the fluorescence m easurements performed so far, which concentrated mainly on NAD(P)H cul ture fluorescence. Biogenic fluorophores such as proteins, coenzymes, and vitamins can simultaneously be detected qualitatively and quantita tively inside and outside the cells. This optical method is noninvasiv e, suitable for in vivo measurements. One whole spectrum (excitation, 250-550 nm; emission, 260-600 nm) with the described parameters is per formed within 1 min, which allows an almost continuous monitoring of t he bioprocess. The technique is ideal for on-line, in situ measurement s via fiber optical systems. Results are presented for cultivations of Claviceps purpurea, Escherichia coli, Saccharomyces cerevisiae, and S phingomonas yanoikuyae. Cell growth and the metabolism of the cells (c hanges from aerobic to anaerobic conditions and uncoupling of the oxid ative phosphorylation) could be detected.