Use of multi-staining flow cytometry to characterise the physiological state of Escherichia coli W3110 in high cell density fed-batch cultures.
High cell density fed-batch fermentations of Escherichia coli W3110 have been carried out at specific growth rates of less than 0.3 h-1, to investigate the effect of glucose limitation on the physiological state of individual cells. After an initial exponential batch phase, the feed rate was held constant and a final dry cell weight of approximately 50 g per litre was achieved. The fermentations were monitored by mass spectrometry whilst measurements of pH, DOC, CFU/mL, TCN, OD500nm and residual glucose concentrations were made. Satisfactory and reproducible results were obtained. Flow cytometric analysis of cells in broth samples, based on either of two multi-staining protocols, revealed a progressive change in cell physiological state throughout the course of the fermentations. From these measurements it was concluded that the loss in reproductive viability towards the end of the fed-batch process is due to cell death and not due to the formation of a "viable but nonculturable state" as had previously been reported. Since the presence of a high proportion of dead or dying cells at any time during a fermentation has a detrimental effect on the synthesis of any desired product it is proposed that an on-line flow cytometric analysis and control strategy could be used as a means of increasing overall process efficiency.
Centre for Bioprocess Engineering, School of Chemical Engineering, The University of Birmingham, Edgbaston, B15 2TT, U.K. c.j.hewitt@bham.ac.uk
C J
CJ
Hewitt
G
G
Nebe-Von Caron
A W
AW
Nienow
C M
CM
McFarlane
D015415:Biomarkers / Q000032:analysis; D001709:Biotechnology / Q000379:methods; D002463:Cell Membrane Permeability; D004926:Escherichia coli / Q000737:chemistry / Q000502:physiology*; D004996:Ethidium / Q000032:analysis; D005285:Fermentation; D005434:Flow Cytometry / Q000379:methods*; D005456:Fluorescent Dyes / Q000032:analysis; D011419:Propidium / Q000032:analysis; D015203:Reproducibility of Results; D013858:Thiobarbiturates / Q000032:analysis
D015415:Biomarkers; D005456:Fluorescent Dyes; D013858:Thiobarbiturates; D011419:Propidium; C025284:bis(1,3-diethylthiobarbiturate)trimethineoxonol; D004996:Ethidium