Applications of bio-capacitance to cell culture manufacturing.

This review focuses on why bio-capacitance has developed to become the standard online method to estimate biomass in cell-based bio-manufacturing processes. There is now a good understanding behind the apparent divergence seen between bio-capacitance and trypan blue based cell counts in the later stage of culture through recent works in the field of process monitoring. Methods for how various authors have been able to correct the bio-capacitance signal when required are discussed in this work. There is also a focus on the diversification and development of the probes for single use and smaller bioreactors. The review then describes the wide range of applications where bio-capacitance probes have been able to improve productivity. It includes on-line process control of perfusion-based processes, predictive feeding control of bioreactors, applications with attached cells and viral production. The work discusses the importance of scalability and the ability to validate the probes prior to manufacture and also reveals the additional process information that can be gleamed from the technology.

Modelling real-time simultaneous saccharification and fermentation of lignocellulosic biomass and organic acid accumulation using dielectric spectroscopy.

Dielectric spectroscopy (DS) is routinely used in yeast and mammalian fermentations to quantitatively monitor viable biomass through the inherent capacitance of live cells; however, the use of DS to monitor the enzymatic break down of lignocellulosic biomass has not been reported. The aim of the current study was to examine the application of DS in monitoring the enzymatic saccharification of high sugar perennial ryegrass (HS-PRG) fibre and to relate the data to changes in chemical composition. DS was capable of both monitoring the on-line decrease in PRG fibre capacitance (C=580 kHz) during enzymatic hydrolysis, together with the subsequent increase in conductivity (G=580 kHz) resulting from the production of organic acids during microbial growth. Analysis of the fibre fractions revealed >50% of HS-PRG lignocellulose had undergone enzymatic hydrolysis. These data demonstrated the utility of DS biomass probes for on-line monitoring of simultaneous saccharification and fermentation (SSF).

On-line Measurements and Control of Viable Cell Density in Cell Culture Manufacturing Processes using Radio-frequency Impedance.

In this work, radio-frequency (RF) impedance is reviewed as a method for monitoring and controlling cell culture manufacturing processes. It is clear from the many publications cited that RF Impedance is regarded as an accurate and reliable method for measuring the live cell bio-volume both on-line and off-line and the technology is also sutable for animal cells in suspension, attached to micro-carriers or immobilized in fixed beds. In cGMP production, RF Impedance is being used in three main areas. Firstly, it is being used as a control instrument for maintaining consistent perfusion culture allowing the bioreactor to operate under optimum conditions for maximum production of recombinant proteins. In the second application it has not replaced traditional off-line live cell counting techniques but it is being used as an additional monitoring tool to check product conformance. Finally, RF Impedance is being used to monitor the concentration of live cells immobilized on micro-carriers or packed beds in cGMP processes where traditional off-line live cell counting methods are inaccurate or impossible to perform.