Monitoring reactor biomass

Clarke, David J.; Blake-Coleman, B.C.; Carr, Robert J.; Calder, Michael R.; Atkinson, Tony

doi:10.1016/0167-7799(86)90241-6

Cited by 41 publications

(14 citation statements)

References 24 publications

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“…Nowadays, there is much interest in (and progress towards) the direct and on-line determination of biomass levels, especially using physical approaches which (alone) permit the registration of biomass in real time (Harris & Kell, 1985a, Clarke et al, 1986Kell et al, 1990). Thus, turbidostats can be imagined in which biomass levels are determined directly using methods other than the optical turbidity of a culture, for use as the feedback signal to the nutrient pump.…”

Section: Aberystwythmentioning

confidence: 99%

The permittistat: a novel type of turbidostat

Markx

Davey

Kell

1991

Journal of General Microbiology

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Baker's yeast was grown in a novel type of turbidostat in which the steady-state biomass level was controlled not by the optical turbidity but by the dielectric permittivity of the suspension at appropriate radio frequencies. Dry weight, fresh weight, the optical density at 600 nm, percentage viability (from methylene blue staining), bud count and ethanol concentration were measured off-line and the cell size distribution was recorded using flow cytometry. Any changes in the physiological properties of the yeast had a negligible effect on the ratio between the permittivity set (and measured) and the steady-state dry weight, fresh weight or optical density of the cultures. The permittistat was found to provide an extremely convenient means for carrying out turbidostatic culture.

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Section: Aberystwythmentioning

confidence: 99%

The permittistat: a novel type of turbidostat

Markx

Davey

Kell

1991

Journal of General Microbiology

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“…The measurement of biomass on-line and in real-time in fermentors is a necessity if turbidostatically controlled continuous cultures are to be used, and the development of sensing devices capable of this task has long been an area of interest (Harris and Kell, 1985;Clarke et al, 1986;Kell et al, 1990, Sonnleitner et al, 1992). An ideal sensing device for measuring the biomass in a fermentor should be sensitive to changes in biomass, but be insensitive to both non-biomass solids and necromass.…”

Section: Discussionmentioning

confidence: 99%

“…A third problem with turbidity measurements is that it is not only biomass that is measured, since necromass, particulate solids, and gas bubbles will all contribute to the optical density to some extent. For these reasons, novel methods for the on-line and realtime measurement of the biomass content of industrial fermentations have long been an area of interest (Harris and Kell, 1985;Clarke et al, 1986;Kell et al, 1990;Sonnleitner et al, 1992). …”

Section: Introductionmentioning

confidence: 99%

Oscillatory, stochastic and chaotic growth rate fluctuations in permittistatically controlled yeast cultures

Davey

Woodward

et al. 1996

Biosystems

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We describe a continuous culture syste,m related to the turbidostat, but using a feedback system based on biomass estimation from the dielectric permittivity of the cell suspension rather than its optical density. It is shown that this system provides an excellent method of maintaining a constant biomass level within a fermentor. The computercontrolled system was able to effect the essentially continuous registration of growth rate by monitoring the rate of medium addition via the time-dependent activity of the pump. At some biomass setpoints for aerobically grown cultures of baker's yeast substantial time-dependent fluctuations in the growth rate of the culture were thereby observed. At some biomass setpoints, however, or under anaerobic conditions, or when using a nonCrabtree yeast, the growth rate was constant, indicating that the fluctuations were inherent to the biological system and not simply a property of the fermentor and control system. A variety of time series analyses (Fourier transformations, Hurst and Lyapunov exponents, the determination of embedding dimension, and non-linear time series predictions based on the methodology of Sugihara and May) were used to demonstrate, for the first time, that as well as stochastic and periodic components these fluctuations exhibited deterministic chaos. 'Trivial predictors' were unable to give accurate predictions of the growth rate in these cultures. The growth rate fluctuations were studied further by means of offline measummenta of changes in percentage viability, bud count, and in the external ethanol and glucose concentrations; these data and other evidence suggested that the growth rate fluctuations were closely linked to the primary respirofermentative metabolism of this organism. The identification of chaotic growth rates in cell cultures suggests that there may be novel methods for controlling the growth of such cultures.

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“…These control systems are often dependent on inline/online/at-line detection systems, such as high-performance liquid chromatography (HPLC) for metabolites, off-gas balance, and/or dielectric spectroscopy measurements. The use of accurate and reliable biomass measurement systems [3,4], especially of viable cell concentrations (VCCs), enables proper process control tools, which lead subsequently to more robust and reliable bioprocesses. The VCC is measured using offline measurement principles including marker proteins or fluorescence probes, such as flow cytometry or confocal microscopy [5,6].…”

Section: Introductionmentioning

confidence: 99%

Low-Frequency Electrochemical Impedance Spectroscopy as a Monitoring Tool for Yeast Growth in Industrial Brewing Processes

et al. 2017

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Today's yeast total biomass and viability measurements during the brewing process are dependent on offline methods such as methylene blue or florescence dye-based staining, and/or the usage of flow cytometric measurements. Additionally, microscopic cell counting methods decelerate an easy and quick prediction of yeast viability. These processes are time consuming and result in a time-delayed response signal, which not only reduces the knowledge of the performance of the yeast itself, but also impacts the quality of the final product. Novel approaches in process monitoring during the aerobic and anaerobic fermentation of Saccharomyces cerevisiae are not only limited to classical pH, dO 2 and off-gas analysis, but they also use different in situ and online sensors based on different physical principles to determine the biomass, product quality and cell death. Within this contribution, electrochemical impedance spectroscopy (EIS) was used to monitor the biomass produced in aerobic and anaerobic batch cultivation approaches, simulating the propagation and fermentation unit operation of industrial brewing processes. Increases in the double-layer capacitance (C DL ), determined at frequencies below 1 kHz, were proportional to the increase of biomass in the batch, which was monitored in the online and inline mode. A good correlation of C DL with the cell density was found. In order to prove the robustness and flexibility of this novel method, different state-of-the-art biomass measurements (dry cell weight-DCW and optical density-OD) were performed for comparison. Because measurements in this frequency range are largely determined by the double-layer region between the electrode and media, rather minor interferences with process parameters (aeration and stirring) were to be expected. It is shown that impedance spectroscopy at low frequencies is not only a powerful tool for the monitoring of viable yeast cell concentrations during operation, but it is also perfectly suited to determining physiological states of the cells, and may facilitate biomass monitoring in the brewing and yeast-propagating industry drastically.

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Monitoring reactor biomass

Cited by 41 publications

References 24 publications

The permittistat: a novel type of turbidostat

The permittistat: a novel type of turbidostat

Oscillatory, stochastic and chaotic growth rate fluctuations in permittistatically controlled yeast cultures

Low-Frequency Electrochemical Impedance Spectroscopy as a Monitoring Tool for Yeast Growth in Industrial Brewing Processes

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