Fig. 5

Histogram distributions of at-line analyzed samples during the fed-batch process for L- phenylalanine production in a stirred-tank bioreactor with Escherichia coli 4RP. Stacked histograms show the expressed fluorescence intensities against the relative cell count for the four markers mTagBFP2 (blue marker, general stress response), mEmerald (green marker, growth behavior), CyOFP1 (orange marker, oxygen limitation) and mCardinal2 (red marker, product formation). The corresponding time stamps of each histogram are listed on the right. Plots with a white background represent histograms during the initial batch phase, whereas histograms with an orange or grey background derive from the biomass production phase or product formation phase, respectively. The verticals in each stacked histogram layer marks a signal intensity of 6∙10². The x axis is scaled bi-exponentially