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Fig. 1 | Microbial Cell Factories

Fig. 1

From: Metabolic fluxes-oriented control of bioreactors: a novel approach to tune micro-aeration and substrate feeding in fermentations

Fig. 1

Schematic representation of the proposed control strategy for the Flux-based Micro-aerated control fermentation (FMC). a Simulated ethanol fluxes using the genome-scale metabolic model (GSM) of S. cerevisiae iND750 for different glucose and oxygen fluxes as inputs. The gray shaded area in A represents the maximum GSM simulated \({\text{J}}_{\text{EtOH}}^{\text{MM}}\) region. \({\text{J}}_{{{\text{O}}_{2} }}^{\text{MM}}\)—simulated oxygen flux; \({\text{J}}_{\text{EtOH}}^{\text{MM}}\)—simulated ethanol flux; \({\text{J}}_{\text{S}}^{\text{MM}}\)—simulated substrate flux. b FMC control framework, with RQ as the controlled variable, and both QAIR and F as manipulated variables. Fluxes: \({\text{J}}_{\text{S}}^{\text{MC}}\) and \({\text{J}}_{{{\text{O}}_{2} }}^{\text{MC}}\)—mathematical correlation substrate and O2 flux; \({\text{J}}_{{{\text{O}}_{2} }}^{\text{CA}}\) and \({\text{J}}_{{{\text{O}}_{2} }}^{\text{CA}}\)—O2 and CO2 fluxes calculated on-line by the control algorithm; \({\text{RQ}}_{{}}^{\text{CA}}\)—respiratory quotient calculated on-line. Equipment: As-computational monitoring and supervision system SuperSys_Ferm; Bs—Bath; C—CO2 analyzer; D—O2 analyzer; E—cFP-FieldPoint; K—Impeller speed controller; G—Air flow controller; H—Nitrogen flow controller; I—feed pump. Dashed lines—information. Control loops: control of oxygen consumption (Air flow rate—QAIR, Eq. B2.3; Nitrogen flow rate—iQN2) (in red); control of substrate consumption (Feed flow rate—F, Eq. B2.1) (in lilac); Controlled variable (RQ) (in green). Some lines of acquisition and communication with the field point are omitted. All fluxes in mmol g DW −1  h−1. *Mathematical correlations in Results Metabolic Models Simulations and Correlations (Eqs. 1 and 2, respectively)

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