Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Aug;45(8):931-938.
doi: 10.1007/s10529-023-03384-w. Epub 2023 May 25.

Determining the linear correlation between dielectric spectroscopy and viable biomass concentration in filamentous fungal fermentations

Atli Magnússon  1   2 , Jari Pajander  3 , Gürkan Sin  3   4 , Stuart Stocks  3   4
Affiliations

Determining the linear correlation between dielectric spectroscopy and viable biomass concentration in filamentous fungal fermentations

Atli Magnússon et al. Biotechnol Lett. 2023 Aug.

Abstract

Objectives: Dielectric spectroscopy is commonly used for online monitoring of biomass growth. It is however not utilized for biomass concentration measurements due to poor correlation with Cell Dry Weight (CDW). A calibration methodology is developed that can directly measure viable biomass concentration in a commercial filamentous process using dielectric values, without recourse to independent and challenging viability determinations.

Results: The methodology is applied to samples from the industrial scale fermentation of a filamentous fungus, Acremonium fusidioides. By mixing fresh and heat-killed samples, linear responses were verified and sample viability could be fitted with the dielectric [Formula: see text] values and total solids concentration. The study included a total of 26 samples across 21 different cultivations, with a legacy at-line viable cell analyzer requiring 2 ml samples, and a modern on-line probe operated at-line with 2 different sample presentation volumes, one compatible with the legacy analyzer, a larger sample volume of 100 ml being compatible with calibration for on-line operation. The linear model provided an [Formula: see text] value of 0.99 between [Formula: see text] and viable biomass across the sample set using either instrument. The difference in ∆C when analyzing 100 mL and 2 mL samples with an in-line probe can be adjusted by a scalar factor of 1.33 within the microbial system used in this study, preserving the linear relation with [Formula: see text] of 0.97.

Conclusions: It is possible to directly estimate viable biomass concentrations utilizing dielectric spectroscopy without recourse to extensive and difficult to execute independent viability studies. The same method can be applied to calibrate different instruments to measure viable biomass concentration. Small sample volumes are appropriate as long as the sample volumes are kept consistent.

Keywords: Dielectric spectroscopy; Fermentation; Sensor calibration; Viable biomass.

PubMed Disclaimer

Conflict of interest statement

None.

Figures

Fig. 1
Fig. 1
Comparison of measured CDW and ΔC. Dielectric spectroscopy of certain samples is measured in the Viable Cell Analyzer and others using the annular probe. No single sample is measured on both instruments
Fig. 2
Fig. 2
Differences in permittivity increment (ΔC) at different dilution levels. Figure 2a Shows a single sample in the stationary phase measured on the Viable Cell Analyzer at an increment of approx. 0.1 fresh sample mass fraction. Figure 2b shows the permittivity increment of three selected samples to represent different fermentation phases at different dilution levels, measured on the Annular Probe
Fig. 3
Fig. 3
Determination of hidden relation between viable biomass and ΔC after applying the viable fraction corrections on CDW measurements. Two independent calibrations are obtained depending on the measurement device used for ΔC
Fig. 4
Fig. 4
The difference in ΔC when measuring the same fresh samples with different sample volumes when using the annular probe. Viable biomass is calculated using the linear correlation calibrated with the 2 mL samples measured with the annular probe
See this image and copyright information in PMC

Similar articles

See all similar articles

References

    1. Dahene WV, Jahnsen S, Kirk I, Larsen R, Lorck H. Fusidic acid: Properties, biosynthesis, and fermentation. In: Vandamme EJ, editor. Biotechnology of industrial antibiotics. New York: Illustrated, Marcel Dekker; 1984. pp. 427–450.
    1. Ehgartner D, Hartmann T, Heinzl S, Frank M, Veiter L, Kager J, Herwig C, Fricke J. Controlling the specific growth rate via biomass trend regulation in filamentous fungi bioprocesses. Chem Eng Sci. 2017;172:32–41. doi: 10.1016/j.ces.2017.06.020. - DOI
    1. Fernandes J, Currie J, Ramer K, Zhang A. Development of capacitance tools: At-line method for assessing biomass of mammalian cell culture and fixed cell calibration standard. Biotechnol J. 2019;14(4):1–26. doi: 10.1002/biot.201800283. - DOI - PubMed
    1. Flores-Cosío G, Herrera-López EJ, Arellano-Plaza M, Gschaedler-Mathis A, Sanchez A, Amaya-Delgado L. Dielectric property measurements as a method to determine the physiological state of Kluyveromyces marxianus and Saccharomyces cerevisiae stressed with furan aldehydes. Appl Microbiol Biotechnol. 2019;103(23–24):9633–9642. doi: 10.1007/s00253-019-10152-2. - DOI - PubMed
    1. Kell DB, Kaprelyants AS, Weichart DH, Harwood CR, Barer MR. Viability and activity in readily culturable bacteria: A review and discussion of the practical issues. Antonie Van Leeuwenhoek, International Journal of General and Molecular Microbiology. 1998;73(2):169–187. doi: 10.1023/A:1000664013047. - DOI - PubMed

LinkOut - more resources