On-line Capacitance Measurement Research Articles

Monitoring online biomass with a capacitance sensor during scale-up of industrially relevant CHO cell culture fed-batch processes in single-use bioreactors

In 2004, the FDA published a guideline to implement process analytical technologies (PAT) in biopharmaceutical processes for process monitoring to gain process understanding and for the control of important process parameters. Viable cell concentration (VCC) is one of the most important key performance indicator (KPI) during mammalian cell cultivation processes. Commonly, this is measured offline. In this work, we demonstrated the comparability and scalability of linear regression models derived from online capacitance measurements. The linear regressions were used to predict the VCC and other familiar offline biomass indicators, like the viable cell volume (VCV) and the wet cell weight (WCW), in two different industrially relevant CHO cell culture processes (Process A and Process B). Therefore, different single-use bioreactor scales (50–2000 L) were used to prove feasibility and scalability of the in-line sensor integration. Coefficient of determinations of 0.79 for Process A and 0.99 for Process B for the WCW were achieved. The VCV was described with high coefficients of determination of 0.96 (Process A) and 0.98 (Process B), respectively. In agreement with other work from the literature, the VCC was only described within the exponential growth phase, but resulting in excellent coefficients of determination of 0.99 (Process A) and 0.96 (Process B), respectively. Monitoring these KPIs online using linear regression models appeared to be scale-independent, enabled deeper process understanding (e.g. here demonstrated in monitoring, the feeding profile) and showed the potential of this method for process control.

Study on production enhancement of validamycin A using online capacitance measurement coupled with 1H NMR spectroscopy analysis in a plant-scale bioreactor

Abstract Herein, an improved production of validamycin A was obtained upon developing a fed-batch strategy in a plant-scale bioreactor. The shift in metabolic flux during validamycin A fermentation process was elucidated using the online capacitance measurement coupled with 1H NMR spectroscopy. We found that the online capacitance measurement could replace DCW for biomass detection in raw material medium during fermentation. On the basis of cell mass and residual sugar concentration, a fed-batch fermentation strategy was developed, with two times addition of 12 g/L glucose in the broth at the 49.5th and 64.5th h. Subsequently, the validamycin A concentration reached 26.0 g/L in a 60-T fermenter. The intracellular concentration of trehalose, maltose, and tryptophan had notably increased, and their accumulation had a strong relationship with validamycin A production. In this study, a metabolomics analysis method without 13C labeling, which can be applied to plant-scale fermentation in turbid broth, is being presented for the first time. In brief, the undertaken study provides a new approach for the process improvement of validamycin A production.

Controlling the feed rate of propanol to optimize erythromycin fermentation by on-line capacitance and oxygen uptake rate measurement.

The aim of the present study was to optimize the feeding proportion of glucose and propanol for erythromycin biosynthesis by real-time monitoring and exploring its limited ratio by the on-line multi-frequency permittivity measurement. It was found that the capacitance values were sensitive to the variation of biomass concentration and microbial morphology as well as the true state of cell growth. It was most favorable to both cell growth and secondary metabolism to keep the ratio of glucose to propanol at 4.3 (g/g). The specific growth rate calculated by the capacitance measurement correctly and accurately reflected the cell physiological state. An appropriate feed rate of propanol was crucial for cell growth and secondary metabolism, as well as to improve the quality of erythromycin-A. In addition, the erythromycin production titer (10,950 U/mL) was further enhanced by 4 % when the propanol feed was regulated by step-down strategy based on both OUR (oxygen uptake rate) and the on-line monitoring capacitance.

Estimation of gas void formation in statically cooled waxy crude oil using online capacitance measurement

Waxy crude oil is one of the massively produced petroleum reserves in the oil and gas industry. It possesses two different natures at different conditions. At a temperature above its wax appearance temperature it functions as a Newtonian fluid. Moreover, when it flows in a subsea environment where the temperature drops, the occurrence of non-Newtonian fluid would appear. However, it is mandatory to prevent the pipelines from building up with the solid wax layer, or else a strong paraffinic gel structure would plug the flow of the waxy crude oil. This gel accumulation results in the emergence of thermal shrinkage where gas voids consequently occur. A Malay Basin waxy crude oil has used for this study to investigate the gas void formation in statically cooled waxy crude oil using an online Electrical Capacitance Tomography (ECT) measurement. This paper has been focused on the development of a non-invasive, non-intrusive approach for the visualization of waxy crude oil by applying the ECT system. The online inspection of the behavior of waxy crude oil is important so that the appropriate action can be taken during the gas void formation within a gelled crude oil. An experimental study was conducted on a 1.18in. circular flow loop rig at distinct temperatures to assess the behavior and formation of gas voids formed due to thermal shrinkage. A capacitance sensor with dual planes consisting of eight electrodes per plane was installed on the rig to capture the images and measure the raw capacitance. Gas voids within a range of 8–14% were observed within the gelled crude oil based on different cooling temperatures. It has been found from the analysis that the gas voids follow an increasing trend with a decrease in temperature and cooling rate.

Monitoring inverse-phase emulsion polymerization using electrical impedance spectroscopy

Inverse-phase emulsion polymerization (IEP) is a widely used technique for synthesizing polyacrylamide, a product in demand for water treatment and in food industries. Despite its extensive application, challenges exist in controlling and monitoring IEP due to the relatively high polymerization rate and high viscosity of polyacrylamide. We investigated IEP of acrylamide with an industrial solvent, D80, as the oil phase, azobisisobutyronitrile as an oil-soluble initiator, and a mixture of sorbitan monooleate (Span 80) and poly(oxyethylene sorbitan trioleate) (Tween 85) as emulsifier. Our study showed that electrical impedance spectroscopy (EIS) is an efficient tool for monitoring the progress and characteristics of IEP in real time. The results revealed that the monomer conversion and polymerization rate correlate well with on-line capacitance measurements using EIS at an appropriate frequency, while changes in conductance correlate well with changes in particle diameter which was validated using an off-line dynamic light scattering method. © 2014 Society of Chemical Industry

Self-sensing actuation using online capacitance measurement with application to active vibration control

Self-sensing actuation has been extensively used in vibration control of flexible structures over the last three decades. Positive position feedback controller has been commonly used in this field due to the robustness against spillover phenomena. Piezoelectric clamped capacitance is the most important parameter that affects the performance of this technique. In this study, the effect of capacitance change on performance and stability of a self-sensing system with positive position feedback controller is investigated. Based on this analysis, some modifications are suggested to increase the stability of the closed-loop system against capacitance change. An online Fourier transform–based capacitance measurement method is used, which guarantees good performance and stability of closed-loop system in the presence of capacitance change. Experimental results are also presented to show the effectiveness of this method in vibration control of cantilever beam.

Optimization of polyhydroxyalkanoates fermentations with on-line capacitance measurement

The aim of this work was to provide an effective methodology for optimization of the polyhydroxyalkanoates (PHAs) fermentation with Ralstonia eutropha by the on-line capacitance measurement. The present study found the capacitance values could reflect variations of microbial morphology and viability. Furthermore, oxygen uptake rate, specific oxygen uptake rate and specific growth rate were measured in real-time and compared with the capacitance value. In addition, a fed-batch control strategy based on the on-line capacitance measurement was proposed to improve the PHAs production by 22%.

Automated dynamic fed‐batch process and media optimization for high productivity cell culture process development

Current industry practices for large-scale mammalian cell cultures typically employ a standard platform fed-batch process with fixed volume bolus feeding. Although widely used, these processes are unable to respond to actual nutrient consumption demands from the culture, which can result in accumulation of by-products and depletion of certain nutrients. This work demonstrates the application of a fully automated cell culture control, monitoring, and data processing system to achieve significant productivity improvement via dynamic feeding and media optimization. Two distinct feeding algorithms were used to dynamically alter feed rates. The first method is based upon on-line capacitance measurements where cultures were fed based on growth and nutrient consumption rates estimated from integrated capacitance. The second method is based upon automated glucose measurements obtained from the Nova Bioprofile FLEX® autosampler where cultures were fed to maintain a target glucose level which in turn maintained other nutrients based on a stoichiometric ratio. All of the calculations were done automatically through in-house integration with a Delta V process control system. Through both media and feed strategy optimization, a titer increase from the original platform titer of 5 to 6.3 g/L was achieved for cell line A, and a substantial titer increase of 4 to over 9 g/L was achieved for cell line B with comparable product quality. Glucose was found to be the best feed indicator, but not all cell lines benefited from dynamic feeding and optimized feed media was critical to process improvement. Our work demonstrated that dynamic feeding has the ability to automatically adjust feed rates according to culture behavior, and that the advantage can be best realized during early and rapid process development stages where different cell lines or large changes in culture conditions might lead to dramatically different nutrient demands.

Linear Correlation between Online Capacitance and Offline Biomass Measurement up to High Cell Densities in Escherichia coli Fermentations in a Pilot-Scale Pressurized Bioreactor

To yield high concentrations of protein expressed by genetically modified Escherichia coli, it is important that the bacterial strains are cultivated to high cell density in industrial bioprocesses. Since the expressed target protein is mostly accumulated inside the E. coli cells, the cellular product formation can be directly correlated to the bacterial biomass concentration. The typical way to determine this concentration is to sample offline. Such manual sampling, however, wastes time and is not efficient for acquiring direct feedback to control a fedbatch fermentation. An E. coli K12-derived strain was cultivated to high cell density in a pressurized stirred bioreactor on a pilot scale, by detecting biomass concentration online using a capacitance probe. This E. coli strain was grown in pure minimal medium using two carbon sources (glucose and glycerol). By applying exponential feeding profiles corresponding to a constant specific growth rate, the E. coli culture grew under carbon-limited conditions to minimize overflow metabolites. A high linearity was found between capacitance and biomass concentration, whereby up to 85 g/L dry cell weight was measured. To validate the viability of the culture, the oxygen transfer rate (OTR) was determined online, yielding maximum values of 0.69 mol/l/h and 0.98 mol/l/h by using glucose and glycerol as carbon sources, respectively. Consequently, online monitoring of biomass using a capacitance probe provides direct and fast information about the viable E. coli biomass generated under aerobic fermentation conditions at elevated headspace pressures.

The influence of quantization process on the performance of global entropic thresholding algorithms using electrical capacitance tomography data

In measuring component fraction in multiphase flows using tomographic techniques, it is desirable to use a high speed tomography system capable of generating 100 tomograms per second. The electrical capacitance tomography system in this regard is considered to be the best among the available tomographic techniques. However, due to its inherent limitations the system generates distorted reconstructed tomograms necessitating the use of extra signal processing techniques such as thresholding to minimize these distortions. Whilst thresholding technique has been effective in minimizing distortions, the additional computation associated with the process limits the speed of tomogram generation desired from the system. Further, the accuracy of the techniques is limited to higher ranges of the full component fraction range. However, since its performance can be influenced by the nature of the quantization process required a priori, optimal quantization parameters can be found and used to improve performance. In this article the influence of quantization resolution and its rate on the performance of global entropic thresholding algorithms have been investigated. Measurement of gas volume component fraction in a multiphase flow of gas/liquid mixture using electrical capacitance tomography system has been used for evaluation using simulated and online capacitance measurement data. Results show that an optimal quantizer resolution is flow regime dependent. Higher resolutions are optimal for annular flow and vice versa for stratified flow regimes. Also, higher resolution significantly minimizes the dependency of the thresholding algorithm on the object to be searched, thereby reducing complexity of designing a thresholder. Overall, the optimal quantization resolution is 256. Tanzania Journal of Science Vol. 31 (2) 2005: pp. 63-76

Real-time viable-cell mass monitoring in high-cell-density fed-batch glutathione fermentation by Saccharomyces cerevisiae T65 in industrial complex medium

An on-line monitoring of viable-cell mass in high-cell-density fed-batch cultivations of Saccharomyces cerevisiae grown on an industrial complex medium was performed with an in situ capacitance probe fitted to a 50-l fermentor. Conventional off-line biomass determinations of several parameters, including dry cell weight (DCW), optical density at 600 nm wavelength (OD(600)), packed mycelial volume (PMV) and number of colony forming units (CFU), were performed throughout the bioprocess and then compared with on-line viable-cell concentrations measured using a capacitance probe. Capacitance versus viable biomass and all off-line biomass assay values were compared during glutathione fermentation in industrial complex culture media. As a result, the relationship between the number of colony forming units and capacitance with a correlation coefficient (R) of 0.995 was achieved. Simultaneously, compared with those determined by at-line indirect estimation methods including oxygen uptake rate (OUR) and carbon dioxide evolution rate (CER), the specific growth rates estimated by on-line capacitance measurement could be more reliable during glutathione fermentation. Therefore, it is concluded that a capacitance probe is a practical tool for real-time viable biomass monitoring in high-cell-density fed-batch cultivation in a complex medium.

Real time monitoring biomass concentration in Streptomyces clavuligerus cultivations with industrial media using a capacitance probe

On-line monitoring biomass concentration in mycelial fed-batch cultivations of Streptomyces clavuligerus grown with soluble and partially insoluble complex media, was investigated with an in-situ capacitance probe fitted to an industrial pilot-plant tank. Standard off-line and on-line biomass determinations, including cell dry weight, packed mycelial volume, viscosity, DNA concentration and total CO 2 evolution in the exhaust gases, were performed throughout the experiments and compared to on-line capacitance measurements. Linear relations between capacitance and all other measurements were developed for both media that hold only in defined process phases, depending on the biomass state and the amount of insoluble matter present. For the industrial complex culture media good linear relations were obtained in the fast growth phase between capacitance and DNA concentration and total CO 2 evolution, while in the subsequent transition and stationary phases only with apparent viscosity was a reasonable correlation found. The capacitance probe was shown to be a valuable tool for real-time monitoring biomass concentration in industrial-like cultivation of mycelial streptomycetes.

On-line biomass monitoring by capacitance measurement

An in-situ, steam-sterilizable capacitance probe was used to follow the biomass concentration on-line, in bioreactors from 20 to 2000 l total volume. Microbial cultures of Saccharomyces cerevisiae, Pichia pastoris and Streptomyces virginiae were grown in batch and fed-batch culture in both defined and complex media in order to demonstrate the wide dynamic operating range of the instrument. A linear correlation was found between the on-line capacitance measurement and the off-line measurements (optical density, OD 620; packed mycelial volume, PMV; biomass concentration X, and colony forming units, CFU ml −1) for biomass concentrations (dry cell weight) up to 30 g l −1 ( St. virginiae), 106 g l −1 ( S. cerevisiae) and 89 g l −1 ( P. pastoris). The on-line capacitance measurement was slightly influenced by variations in agitation speed and strong extraneous radio frequencies. A specific capacitance constant ( C s) was defined for all microbial cells which was dependent on cell viability and cell size. The C s was easy to calculate using the on-line capacitance measurement and an off-line estimation of biomass concentration. The Biomass Monitor proved suitable for precise on-line monitoring of both homogeneous (uni-cellular) and heterogeneous (mycelial) cultures in bioreactors.