Various key variables (biomass, substrate and product) of bioprocesses should be monitored in order to retrieve useful information on the system, with the biomass (the cell density) the principal target. Although several analytical methods have been adapted and used to monitor the evolution of cell density evolution in cultures, a general method for performing this determination has not yet been established, as each technique has its own advantages and drawbacks. In the present work, noninduced glycerol batch cultures (for which biomass and substrate are the key variables) were monitored using multiwavelength fluorescence spectroscopy. The data gathered were modelled via PARAFAC-PLS chemometric methodologies, resulting in important qualitative and quantitative information about the behaviours of different biogenic fluorophors in batch cultures of the yeast Pichia pastoris. This information was used to predict the target process variables in such cultures; this permitted the applicability of this combined technique to bioprocess monitoring to be assessed.
The utilisation of tryptophan fluorescence as an indirect biomass measurement for the yeast Pichia pastoris, an excellent host system for the production of heterologous proteins, is presented. Direct fluorescence measurements for cell densities above 3 g dm −3 presented important interferences due to inner filter effects. To overcome this drawback, a dilution protocol is provided which allows the quenching of the emission signal caused by solid particles to be controlled. The measured tryptophan fluorescence intensities were used to estimate biomass concentration during a P pastoris batch bioprocess growing either on glycerol or methanol. The best measurement model tested was based on the application of a Luedeking-Piret-based equation to fluorometric measurements. Thus, a linear relationship between the specific fluorescence evolution rate and specific growth rate was applied. The mean absolute relative prediction error (MARE) for biomass concentration was about 6%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.