title: Application of adaptive DO-stat feeding control to Pichia pastoris X33 cultures expressing a single chain antibody fragment (scFv).
abstract: In this study, fed-batch cultures of a Pichia pastoris strain constitutively expressing a single chain antibody fragment (scFv) under the control of the glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter were performed in a pilot 50 L bioreactor. Due to the very high cell density achieved within the first 75 h, typically between 140 and 160 g-DCW/L of dry cell weight (DCW), most of the scFv is produced under hard oxygen transfer limitation. To improve scFv productivity, a direct adaptive dissolved oxygen (DO)-stat feeding controller that maximizes glycerol feeding under the constraint of available oxygen transfer capacity was developed and applied to this process. The developed adaptive controller enabled to maximize glycerol feeding through the regulation of DO concentration between 3 and 5 % of saturation, thereby improving process productivity. Set-point convergence dynamics are characterized by a fast response upon large perturbations to DO, followed by a slower but very robust convergence in the vicinity of the boundary with almost imperceptible overshoot. Such control performance enabled operating closer to the 0 % boundary for longer periods of time when compared to a traditional proportional-integral-derivative algorithm, which tends to destabilize with increasing cell density.
authors.affiliation: REQUIMTE, Systems Biology and Engineering Group, DQ/FCT, Universidade Nova de Lisboa, Campus Caparica, Caparica, Portugal.
authors.forename: A R
authors.initials: AR
authors.lastname: Ferreira
authors.forename: F
authors.initials: F
authors.lastname: Ataíde
authors.forename: M
authors.initials: M
authors.lastname: von Stosch
authors.forename: J M L
authors.initials: JM
authors.lastname: Dias
authors.forename: J J
authors.initials: JJ
authors.lastname: Clemente
authors.forename: A E
authors.initials: AE
authors.lastname: Cunha
authors.forename: R
authors.initials: R
authors.lastname: Oliveira
mesh_terms: D000465:Algorithms; D019149:Bioreactors; D005656:Fungal Proteins / Q000235:genetics; D015870:Gene Expression; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D010843:Pichia / Q000235:genetics / Q000254:growth & development*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D057127:Single-Chain Antibodies / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D011994:Recombinant Proteins; D057127:Single-Chain Antibodies; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases