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Production and cleavage of a fusion protein of porcine trypsinogen and enhanced green fluorescent protein (EGFP) in Pichia pastoris

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Abstract

Pharmaceutical grade trypsin is in ever-increasing demand for medical and industrial applications. Improving the efficiency of existing biotechnological manufacturing processes is therefore paramount. When produced biotechnologically, trypsinogen—the inactive precursor of trypsin—is advantageous, since active trypsin would impair cell viability. To study factors affecting cell physiology and the production of trypsinogen in fed-batch cultures, we built a fusion protein of porcine trypsinogen and enhanced green fluorescent protein (EGFP) in Pichia pastoris. The experiments were performed with two different pH values (5.0 and 5.9) and two constant specific growth rates (0.02 and 0.04 1/h), maintained using exponential addition of methanol. All the productivity data presented rely on an active determination of trypsin obtained by proteolysis of the trypsinogen produced. The pH of the medium did not affect cell growth, but significantly influenced specific production of trypsinogen: A 1.7-fold higher concentration of trypsinogen was achieved at pH 5.9 (64 mg/L at 0.02 1/h) compared to pH 5.0. EGFP was primarily used to facilitate detection of intracellular protein over the biosynthetic time course. Using flow cytometry with fluorescence detection, cell disruption was avoided, and protein extraction and purification prior to analysis were unnecessary. However, Western blot and SDS-PAGE showed that cleavage of EGFP-trypsinogen fusion protein occurred, probably caused by Pichia-endogenous proteases. The fluorescence analysis did therefore not accurately represent the actual trypsinogen concentration. However, we gained new experimentally-relevant insights, which can be used to avoid misinterpretation of tracking and quantifying as well as online-monitoring of proteins with the frequently used fluorescent tags.

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Abbreviations

AOX1 :

Alcohol oxidase 1

CDW:

Cell dry weight

EGFP:

Enhanced greed fluorescent protein

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Acknowledgements

This work was supported by the project MSM6046137305 and built on research performed within the Czech-Swiss project with the participation of Lonza AG and Lonza Biotec s.r.o. E!3415 Optytech, 1P05OE189 of Ministry of Education, Youth and Sports of the Czech Republic and the KTI-Project 7403.3;3 LSPP-LS (https://www.aramis.admin.ch/Grunddaten/?ProjectID=21894). The authors thank Zdeněk Voburka for the N-terminal sequencing analysis, Iwo Zamora for help with data analysis, Katrin Hecht for critical reading of the manuscript, and John Brooker and Maggi Lussi Bell for English proofreading.

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Correspondence to Hana Raschmanová.

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Raschmanová, H., Paulová, L., Branská, B. et al. Production and cleavage of a fusion protein of porcine trypsinogen and enhanced green fluorescent protein (EGFP) in Pichia pastoris. Folia Microbiol 63, 773–787 (2018). https://doi.org/10.1007/s12223-018-0619-y

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  • DOI: https://doi.org/10.1007/s12223-018-0619-y

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