title: NADH and flavin fluorescence responses of starved yeast cultures to substrate additions.
abstract: Model experiments were performed with starved yeast (Saccharomyces cerevisiae) cultures in a batch reactor in order to develop a better understanding of NAD(P)H and flavin culture fluorescence. Fluorescence was monitored during aerobic-anaerobic-aerobic transitions and ethanol and glucose substrate addition experiments. Interpretations of the fluorescence responses obtained are provided, with consideration given to redox compartmentation and the formation of ethanol shortly after a glucose addition. An analytical spectrofluorophotometer was interfaced to a personal computer and adapted to measure fluorescence in a bioreactor. This was achieved by the use of quartz fiber-optic waveguides to convert the right-angle cuvette geometry of the analytical spectrofluorophotometer to an open-ended fluorescence probe geometry, resulting in a flexible culture fluorescence apparatus. Features of the apparatus include variable excitation and emission wavelengths, allowing for detection of NAD(P)H or flavin fluorescence, as well as small slit widths, a variable sampling rate, excitation and emission scanning capabilities, and good sensitivity.
authors.affiliation: Department of Chemical Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Siano
authors.forename: R
authors.initials: R
authors.lastname: Mutharasan