title: Mathematical modelling and process optimization of a continuous 5-stage bioreactor cascade for production of poly[-(R)-3-hydroxybutyrate] by Cupriavidus necator.
abstract: 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.
authors.affiliation: Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6/IV, HR-10000 Zagreb, Croatia. phorvat@pbf.hr
authors.forename: Predrag
authors.initials: P
authors.lastname: Horvat
authors.forename: Ivna
authors.initials: I
authors.lastname: Vrana Špoljarić
authors.forename: Markan
authors.initials: M
authors.lastname: Lopar
authors.forename: Aid
authors.initials: A
authors.lastname: Atlić
authors.forename: Martin
authors.initials: M
authors.lastname: Koller
authors.forename: Gerhart
authors.initials: G
authors.lastname: Braunegg
mesh_terms: D019149:Bioreactors; D020118:Cupriavidus necator / Q000254:growth & development*; D006885:Hydroxybutyrates / Q000378:metabolism*; D008954:Models, Biological; D011091:Polyesters / Q000378:metabolism*; D000094122:Polyhydroxybutyrates
chemical_list: D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates