A novel real‐time method to estimate volumetric mass biodensity based on the combination of dielectric spectroscopy and soft‐sensors

Abstract

BACKGROUND The PAT initiative encourages designing, analyzing, and controlling manufacturing through timely measurements. Dielectric measurements and first principle soft‐sensors emerged as valuable real‐time bioprocess analytical PAT tools to improve process understanding and control capabilities. RESULTS The estimation of a novel physiological variable, bio‐density is presented, using a combination of two PAT sensors, dielectric spectroscopy and a soft‐sensor based on first principle elemental balances. Within this contribution, calibrations for the estimation of biomass dry weight using dielectric measurements were found to change in the transition from batch‐ to fed‐batch and within the induction phase for two recombinant E. coli bioprocesses. This was explained by a change in cell size, as indicated by flow cytometric measurements, light microscopy and changes in the beta dispersion dielectric spectrum. Biomass dry weight was accurately determined using a first principle soft‐sensor. The combination of both signals allowed the real‐time estimation of a new physiological variable, interpreted as bio‐density. Applying this concept, batch/fed‐batch and induction phase physiological changes were successfully observed in real time. Furthermore, a correlation with the specific product titer was observed. CONCLUSION This contribution enhances the application spectrum of dielectric measurements and soft‐sensors for the detection of physiological changes and recombinant product estimation, aiming at more efficient design, monitoring and control of bioprocesses as demanded by the process analytical technology (PAT) initiative. © 2014 Society of Chemical Industry

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