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Fig. 4 | Microbial Cell Factories

Fig. 4

From: Easy to use and reliable technique for online dissolved oxygen tension measurement in shake flasks using infrared fluorescent oxygen-sensitive nanoparticles

Fig. 4

Oxygen-limited cultivation of E. coli BL21 (DE3) pRotHi-YFP. a Simultaneous online monitoring of the oxygen transfer rate (OTR) measured with a RAMOS device and the dissolved oxygen tension (DOT) measured via dispersed oxygen-sensitive nanoparticles in the same RAMOS shake flask. b Calculation (Eq. 1) and error estimation (Eq. 2) of the kLa values during RAMOS aeration phases. The total error is represented by the surrounding area while the fraction of each error component is indicated by a different color as explained in the text. For comparison the kLa value (kLaMeier = 370 h−1) estimated according to the correlation of Meier et al. [34] is shown by the solid and dashed (± 27 h−1) dark blue lines. The osmolality was assumed to be constant for the calculation of kLaMeier and taken from the literature (Osmol = 0.68 Osmol kg−1). Cultivation conditions: Synthetic Wilms-MOPS medium with 20 g L−1 glucose, 0.5 g L−1 sorbitol and 0.1 g L−1 oxygen-sensitive nanoparticles, 250 mL RAMOS shake flask, 37 °C, n = 350 rpm, VL = 10 mL, shaking diameter d0 = 50 mm

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