Development of redox potential-driven fermentation process for recombinant protein expression
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ORIGINAL RESEARCH PAPER
Development of redox potential-driven fermentation process for recombinant protein expression Jingjie Guo . Yixuan Wu . Takuji Tanaka . Yen-Han Lin
Received: 24 April 2020 / Accepted: 12 October 2020 Ó Springer Nature B.V. 2020
Abstract Objectives A redox potential-driven fermentation, maintaining dissolved oxygen at a prescribed level while simultaneously monitoring the changes of fermentation redox potential, was developed to guide the cultivation progress of recombinant protein expression. Results A recombinant E. coli harboring prolinaseexpressing plasmid (pKK-PepR2) was cultivated using the developed process. Two distinct ORP valleys were noticeable based on recorded profile. The first ORP valley is equivalent to the timing for the addition of inducing agent, and the second ORP valley serves to guide the timing for cell harvesting. The final prolinase activity is 0.172 lmol/mg/min as compared to that of 0.154 lmol/mg/min where the optical density was employed to guide the timing of inducer addition and an empirically determined length of the cultivation. Conclusion The developed process can be further modified to become an automatic operation.
J. Guo Y. Wu Y.-H. Lin (&) Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, Canada e-mail: [email protected] T. Tanaka Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, Canada
Keywords Fermentation redox potential Recombinant protein Fermentation Bioprocess development Abbreviations DO Dissolved oxygen IPTG Isopropyl b-d-1-thiogalactopyranoside OD Optical density ORP Fermentation redox potential
Introduction Fermentation redox potential (ORP) measures the net balance between oxidation and reduction reaction involved in microbial metabolism. Redox potentialdriven fermentation monitors and optimizes the fermentation process, leading to higher production in desired metabolic product (Liu et al. 2017). This technology had been applied in VHG ethanol fermentation, where the correlation among ORP and Saccharomyces cerevisiae growth pattern, and its metabolic profile had been investigated. The fermentation had its highest efficiency under ORP controlled at - 150 mV (Lin et al. 2010). Since ORP has shown its ability in monitoring microbial growth, it is feasible to replace optical density (OD) measurement in the induction of recombinant protein production. OD is not an ideal indictor
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in reflecting cell metabolic activity. The measurement is based on the amount of light scattered. It measures the turbidity of the culture which is proportional to the cell mass included both living and dead cell. In addition, the frequent sampling from fermentation system increase the risk of being contaminated, and the measurement error can be significant with diluted culture (Stevenson et al. 2016). In this study, instead of using OD, the feasibility of applying ORP to guide the progress of recombinant cell ferme
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