title: Global Sensitivity Analysis for the determination of parameter importance in bio-manufacturing processes.
abstract: The present paper describes the application of GSA (Global Sensitivity Analysis) techniques to mathematical models of bioprocesses in order to rank inputs such as feed titres, flow rates and matrix capacities for the relative influence that each exerts upon outputs such as yield or throughput. GSA enables quantification of both the impact of individual variables on process outputs, as well as their interactions. These data highlight those attributes of a bioprocess which offer the greatest potential for achieving manufacturing improvements. Whereas previous GSA studies have been limited to individual unit operations, this paper extends the treatment to an entire downstream process and illustrates its utility by application to the production of a Fab-based rattlesnake antivenom called CroFab [(Crotalidae Polyvalent Immune Fab (Ovine); Protherics U.K. Limited]. Initially, hyperimmunized ovine serum containing rattlesnake antivenom IgG (product), other antibodies and albumin is applied to a synthetic affinity ligand adsorbent column to separate the antibodies from the albumin. The antibodies are papain-digested into Fab and Fc fragments, before concentration by ultrafiltration. Fc, residual IgG and albumin are eliminated by an ion-exchanger and then CroFab-specific affinity chromatography is used to produce purified antivenom. Application of GSA to the model of this process showed that product yield was controlled by IgG feed concentration and the synthetic-material affinity column's capacity and flow rate, whereas product throughput was predominantly influenced by the synthetic material's capacity, the ultrafiltration concentration factor and the CroFab affinity flow rate. Such information provides a rational basis for identifying the most promising strategies for delivering improvements to commercial-scale biomanufacturing processes.
authors.affiliation: The Advanced Centre for Biochemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK. sunil.chhatre@ucl.ac.uk
authors.forename: Sunil
authors.initials: S
authors.lastname: Chhatre
authors.forename: Richard
authors.initials: R
authors.lastname: Francis
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Newcombe
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Nigel
authors.initials: N
authors.lastname: Titchener-Hooker
authors.forename: Josh
authors.initials: J
authors.lastname: King
authors.forename: Eli
authors.initials: E
authors.lastname: Keshavarz-Moore
mesh_terms: D000327:Adsorption; D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000302:isolation & purification; D001709:Biotechnology / Q000379:methods*; D002846:Chromatography, Affinity / Q000379:methods*; D003198:Computer Simulation; D008024:Ligands; D008954:Models, Biological; D012680:Sensitivity and Specificity; D012756:Sheep; D013499:Surface Properties
chemical_list: D000906:Antibodies; D008024:Ligands