Biotechnology and Bioprocess Engineering 2023; 28(3): 386-397  
Optimization of Process Parameters for Enhanced Production of Ranibizumab in Escherichia coli
Rucha S. Patil, Nidhi Upadhyay, and Anurag S. Rathore
Rucha S. Patil, Nidhi Upadhyay, Anurag S. Rathore*
Department of Chemical Engineering, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India
Tel: +91-11-26591098; Fax: +91-11-26581120
Received: October 19, 2022; Revised: April 19, 2023; Accepted: April 22, 2023; Published online: June 30, 2023.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Escherichia coli based systems, are favoured hosts for recombinant protein expression. However, Low Fab expression and high production costs are major obstacles for manufacturers. To enhance process economics, an efficient, well-defined upstream process is crucial. This paper presents a systematic approach of process optimization for production of Fab fragment, ranibizumab. A two-step design of experiments (DOE) approach has been used. Six variables were examined: post-induction temperature, postinduction time, inducer concentration, agitation speed, media pH, and cell density at induction time (induction OD). These parameters were evaluated for their effect on biomass concentration, protein titre, impurity level, and light to heavy chain ratio. First, screening DOE with fractional factorial design was performed to shortlist important process parameters. Next, response surface study based on central composite design was conducted for identifying the operating range for the significant process parameters. Induction OD, inducer concentration, pH, and temperature were identified as significant parameters with their respective optima at 1.2 OD, 1 mM, 7.4 pH, and 35°C, respectively. Operating under these conditions resulted in formation of 0.051 g protein/g inclusion bodies, 4.99 g/L biomass concentration, and light chain to heavy chain equal expression ratio (LC:HC=0.98), with 8.2% impurity. Additionally, based on the predictions, we found that temperature, induction OD, and their interactions significantly affect the LC:HC ratio and impurity level, and need to be tightly controlled. This study has highlighted the importance of fine-tuning of physical parameters for production of Fab fragments and to control impurity expression in microbial host systems.
Keywords: inclusion bodies, process optimization, Fab fragment, design of experiments, response surface methodology, ranibizumab

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