Fig. 2
Setting up aerobic retentostat cultures. a Retentostat cultures (bioreactors) were started from a steady-state chemostat culture with an ingoing glucose concentration (CS,MC) of 20 g L−1. At the start of the retentostats (t = 0 h), the feed to the mixing vessel was switched to the medium reservoir for the retentostat cultivation (as indicated by the arrow). The process was modelled for three different concentrations of glucose in the medium reservoir for the retentostat cultures (CS,MR). b Profiles of biomass concentration (CX), specific glucose consumption rate (qS) and specific growth rate (µ) in time were predicted with a mathematical model, based on glucose concentration in the feed coming from the mixing vessel. Blue lines indicate a scenario in which CS,MC = CS,MR = 20 g L−1, green lines indicate CS,MR = 5 g L−1, and red lines indicate CS,MR = 7.5 g L−1. Dotted lines indicate simulations for which 10 % higher or lower maintenance values were considered in the model (see “Methods” section). The operational conditions applied in the experiments in this study correspond to the red lines