Statistical approach for media optimization of fHbp–PorA chimeric protein expression in <i>Escherichia coli</i> ; development of a promising Meningococcal B vaccine

Successful design of an industrial biological product such as a vaccine requires an efficient, robust and reproducible process. In this study, we investigated conditions for process optimization of a promising recombinant factor H binding protein (fHbp)-Porin A (PorA) chimeric protein-based vaccine candidate against Meningococcal B serogroup in Escherichia coli B834 strain using the inducible T7-lac promoter system. Random screening of components of complex culture media for growth and expression using IPTG as an inducer, showed inconsistency when analyzed using Plackett-Burman design (PBD). Further analysis identified galactose present either in tryptone (as lactose) or soy-phytone, has caused strong autoinduction and is surmised as an interfering factor for IPTG induction. Synergistic combination of soy-phytone and yeast extract under conditions of controlled growth and auto-induction gave a good correlation between the cell growth and expression of the fHbp-PorA chimeric protein when evaluated using PBD and central composite design. Using response optimization conditions, an optimized media was attained. A shake flask study was performed to validate the optimized media, and later, a fed-batch fermentation at 10 L scale was established to prove the scalability, consistency, and product quality using the optimized media. One-sentence summary This study reports optimization of cell growth and expression conditions for a recombinant chimeric meningococcal protein in E. coli that assures its industrial scale production and suitability for preclinical and clinical studies as a vaccine component against Meningococcal B serogroup.