Influence of phosphate limitation on respiration activity during cultivation. The oxygen transfer rate (OTR) was measured with the RAMOS device. In panel (A), the mean (n = 2) and standard deviations of duplicate cultivations with 3000 mg/L K2HPO4 (•, blue), 150 mg/L K2HPO4 (■, red) and 75 mg/L K2HPO4 (▲, green) are depicted. In separate shake flasks, samples were collected and analysed for glucose, acetate and phosphate (PO43-). The results of these analyses and the OTR are depicted in (B) for 3000 mg/L, in (C) for 150 mg/L and in (D) for 75 mg/L K2HPO4. The cultivation conditions were as follows: 37°C, shaking diameter 50 mm, shaking frequency 350 rpm, filling volume 10 mL, no induction; modified Wilms & Reuss medium (7.5 g/L Glucose) with various phosphate contents.