Flow cytometry is an established tool in fundamental studies of single-cell microbial physiology. Here we show that it can also provide valuable information for process development. Using recombinant Escherichia coli strains, which express the protein-based polymer (GVGIP)260GVGVP, the utility of flow cytometry in monitoring and optimization of fermentations is demonstrated. Single cell right angle light scatter was found to be significantly affected by intracellular product formation possibly due to the formation of inclusion bodies. Translational fusions with green fluorescent protein (GFP) enabled monitoring of product accumulation, as well as plasmid free cell fraction (PFCF). Such fusions also allowed rapid evaluation of induction strategies and three different expression systems based on the T7 promoter, T7-lac promoter and the PBAD promoter. The expression system based on the PBAD promoter was found to be superior to the T7-based system.
Bibliographical noteFunding Information:
We thank the Office of Naval Research for supporting this work. Dr Xu and Dr McPherson of Bioelastics Research Limited (BRL), Birmingham, AL, provided valuable assistance in this study.
Copyright 2008 Elsevier B.V., All rights reserved.
- Escherichia coli
- Flow cytometry