Fig. 7.

Comparison of shake flask and stirred tank reactor cultivations of Bacillus licheniformis DSM 8785. As indicated by the vertical dotted lines, the shaking frequency of the shake flask cultivation (a–c) and the agitation rate of the stirred tank reactor cultivation (d–f) were reduced from 350 to 100 and from 1000 to 500 rpm after 4.5 and 3 h, respectively. The courses of oxygen transfer rates (OTR) and respiratory quotients (RQ) (a, d), glucose and total 2,3-butanediol concentrations (b, e) as well as cell dry weight, acetoin and glycerol concentrations (c, f) are shown. In addition to offline samples (half-closed symbols), the concentrations upon glucose depletion were calculated as described in Fig. 4 (closed symbols). For clarity, the connections between the measured and calculated values are shown as dotted lines. 2,3-Butanediol is shown as sum of the stereoisomers. The RQ is only shown for OTR > 1 mmol/L/h. To account for the increase of metabolite concentrations due to evaporation of water, concentrations of the shake flask cultivation were corrected accordingly and referred to the initial filling volume. Cultivation conditions: Temperature: 37 °C; shake flask cultivation: 250 mL unbaffled shake flasks, filling volume: 30 mL, shaking frequency: 350/100 rpm, shaking diameter: 50 mm; stirred tank reactor cultivation: 2 L stirred tank reactor, filling volume: 1.5 L, aeration rate: 0.5 L/min (0.33 vvm), agitation rate: 1000/500 rpm