Fig. 7
From: Highly efficient fermentation of 5-keto-d-fructose with Gluconobacter oxydans at different scales
Extended-batch-cultivation of G. oxydans 621H ΔhsdR pBBR1p264-fdhSCL-ST in a 150 L pressurised fermenter (Frings) with constant feeding of fructose (745 g/L) between 22 and 52 h. Depicted is A the oxygen transfer rate (OTR, light blue), carbon dioxide transfer rate (CTR, orange) and respiratory quotient (RQ, dark red), B the dissolved oxygen tension (DOT, dark blue) and aeration rate (light green), C pH (pink), headspace overpressure (green) and filling volume (grey), D the optical density OD600 (purple) and osmolality (black), E fructose (light blue) and 5-ketofructose concentration (red). Cultivation was performed in complex medium (concentrated 1.6×) with 150 g/L initial fructose at 30 °C, initial pH value 6, pH control at 5 from 22 h with 3 M KOH, VL,start = 50 L in a 150 L pressurised fermenter (Frings). DOT was kept ≥ 30% by variation of headspace overpressure (1–1.8 bar), agitation rate: 600 rpm, absolute aeration rate Qg = 50–170 SL/min was increased linearly in parallel to the headspace overpressure. Feeding solution: 745 \(\pm\) 25 gfructose/L, heat pretreatment: 100 °C, 4 h. Feed rate: 900 gfructose/h. Fructose feeding solution was heated to ~ 50 °C. RQ-values are only shown, when OTR-values are above 5 mmol/L/h. Due to technical problems between 22 and 26 h, 32 and 35 h, and 54 and 66 h, OTR, CTR and RQ data shown in dashed lines are not reliable and were approximated by straight lines. For raw data please refer to Additional file 1: Fig. S7