Fig. 2

Cultivation of Bacillus licheniformis DSM 8785 under oxygen-limited conditions. Variation of the filling volume results in different maximum oxygen transfer capacities in shake flask cultivations. Data on oxygen transfer rate (OTR) (a), respiratory quotient (RQ) (b) total 2,3-butanediol concentration (c) and pH (d) are depicted. 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, all concentrations were corrected accordingly and referred to the initial filling volume. Cultivation conditions: 250 mL unbaffled shake flasks, temperature: 37 °C, shaking frequency: 100 rpm, shaking diameter: 50 mm, Nakashimada medium without addition of MES buffer