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Mathematical modelling and process optimization of a continuous 5-stage bioreactor cascade for production of poly[-(R)-3-hydroxybutyrate] by Cupriavidus necator


A multistage system for poly(hydroxyalkanoate) (PHA) production consisting of five continuous stirred tank reactors in series (5-CSTR) with Cupriavidus necator DSM 545 as production strain was modelled using formal kinetic relations. Partially growth-associated production of PHA under nitrogen limited growth was chosen as modelling strategy, thus the Luedeking-Piret’s model of partial growth-associated product synthesis was applied as working hypothesis. Specific growth rate relations adjusted for double substrate (C and N source) limited growth according to Megee et al. and Mankad-Bungay relation were tested. The first stage of the reactor cascade was modelled according to the principle of nutrient balanced continuous biomass production system, the second one as two substrate controlled process, while the three subsequent reactors were adjusted to produce PHB under continuous C source fed and nitrogen deficiency. Simulated results of production obtained by the applied mathematical models and computational optimization indicate that PHB productivity of the whole system could be significantly increased (from experimentally achieved 2.14 g L−1 h−1 to simulated 9.95 g L−1 h−1) if certain experimental conditions would have been applied (overall dilution rate, C and N source feed concentration). Additionally, supplemental feeding strategy for switching from batch to continuous mode of cultivation was proposed to avoid substrate inhibition.

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This work was supported by the Collaborative EU FP7 project ANIMPOL (Biotechnological conversion of carbon containing wastes for eco-efficient production of high added value products; Grant agreement no.: 245084).

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Correspondence to Predrag Horvat.

Electronic supplementary material

Below is the link to the electronic supplementary material.


Online Resource 1: Simulated and experimental results of FM1 when Mankad-Bungay spec. growth rate relation was applied; (P, PHB concentration; CDM, cell dry matter; S, glucose concentration) (TIFF 216 kb)


Online Resource 2: Simulated and experimental results of FM2 when Mankad-Bungay spec. growth rate relation was applied; (P, PHB concentration; CDM, cell dry matter; S, glucose concentration) (TIFF 222 kb)


Online Resource 3: Simulated and experimental results of FM3 when Mankad-Bungay spec. growth rate relation was applied; (P, PHB concentration; CDM, cell dry matter; S, glucose concentration) (TIFF 211 kb)


Online Resource 4: Specific non growth associated PHB production rate inhibition by nitrogen source concentration and biomass productivity in dependence on inflow rate (TIFF 102 kb)


Online Resource 5: Optimized 5-stage cultivation when Mankad-Bungay spec. growth rate relation was applied; (P, PHB concentration; CDM, cell dry matter; S, glucose concentration) (TIFF 181 kb)

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Horvat, P., Vrana Špoljarić, I., Lopar, M. et al. Mathematical modelling and process optimization of a continuous 5-stage bioreactor cascade for production of poly[-(R)-3-hydroxybutyrate] by Cupriavidus necator . Bioprocess Biosyst Eng 36, 1235–1250 (2013).

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  • Continuous production
  • Cupriavidus necator
  • Mathematical modelling
  • Multistage fermentation
  • Poly (3-hydroxybutyrate)