Fig. 7
Extended batch cultivation of G. oxydans 621H ΔhsdR pBBR1p264-FDH-ST in a 2 L fermenter in Gluconobacter minimal medium (GMM) developed in this work. Depicted is A the oxygen transfer rate (OTR, light blue), carbon dioxide transfer rate (CTR, orange) and respiratory quotient (RQ, brown), B the optical density OD600 (olive) and pH (dark blue), C the dissolved oxygen tension (DOT, black) and agitation speed (purple), D fructose (dark red) and 5-ketofructose concentration (turquoise). Cultivation was performed in Gluconobacter minimal medium (GMM) with 150 g/L fructose at 30 °C, initial pH value 6, pH control at 5 from 22 h with 10 M KOH, VL,start = 1 L in a 2 L fermenter. DOT was kept ≥30% by variation of the agitation speed (500–1000 rpm), absolute aeration rate Qg = 1 L/min. Feeding solution: 825 gfructose/L, Feed rate: 15.5 gfructose/h, tfeed = 22–71 h. RQ-values are only shown, when OTR-values are above 5 mmol/L/h