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An innovative, Raman spectroscopy‐based monitoring and control system is introduced in this paper for designing dynamic feeding strategies that allow the maintenance of key cellular nutrients at an ideal level in Chinese hamster ovary cell culture. The Partial Least Squares calibration models built for glucose, lactate and 16 (out of 20) individual amino acids had very good predictive power with low root mean square errors values and high square correlation coefficients. The developed models used for real‐time measurement of nutrient and by‐product concentrations allowed us to gain better insight into the metabolic behavior and nutritional consumption of cells. To establish a more beneficial nutritional environment for the cells, two types of dynamic feeding strategies were used to control the delivery of two‐part multi‐component feed media according to the prediction of Raman models (glucose or arginine). As a result, instead of high fluctuations, the nutrients (glucose together with amino acids) were maintained at the desired level providing a more balanced environment for the cells. Moreover, the use of amino acid‐based feeding control enabled to prevent the excessive nutrient replenishment and was economically beneficial by significantly reducing the amount of supplied feed medium compared to the glucose‐based dynamic fed culture.

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The use of Process Analytical Technology tools coupled with chemometrics has been shown great potential for better understanding and control of mammalian cell cultivations through real-time process monitoring. In-line Raman spectroscopy was utilized to determine the glucose concentration of the complex bioreactor culture medium ensuring real-time information for our process control system. This work demonstrates a simple and fast method to achieve a robust partial least squares calibration model under laboratory conditions in an early phase of the development utilizing shake flask and bioreactor cultures. Two types of dynamic feeding strategies were accomplished where the multi-component feed medium additions were controlled manually and automatically based on the Raman monitored glucose concentration. The impact of these dynamic feedings was also investigated and compared to the traditional bolus feeding strategy on cellular metabolism, cell growth, productivity, and binding activity of the antibody product. Both manual and automated dynamic feeding strategies were successfully applied to maintain the glucose concentration within a narrower and lower concentration range. Thus, besides glucose, the glutamate was also limited at low level leading to reduced production of inhibitory metabolites, such as lactate and ammonia. Consequently, these feeding control strategies enabled to provide beneficial cultivation environment for the cells. In both experiments, higher cell growth and prolonged viable cell cultivation were achieved which in turn led to increased antibody product concentration compared to the reference bolus feeding cultivation.

The aim of this study was to develop a new, easily performable feedback control of crystallization based on the exact polymorphic concentration (mass ratio of polymorph/solvent). The efficiency of the developed process control, utilizing combined signals of inline Raman and attenuated total reflectance ultraviolet visible sensors, was tested in a cooling crystallization of carvedilol. The solution concentration was determined according to multivariate calibration results of UV/vis spectroscopic detection, while the evaluation of the composition of the solid phase was performed by means of Raman spectroscopy assisted by the classical leastsquare method resulting in spectral concentrations. Polymorphic concentrations were obtained by calculating the current solid phase concentration from UV/vis data, and then this value was proportionated to the Raman spectral concentrations of different polymorphs. The real-time parallel evaluation of Raman and UV spectra was performed with the assistance of a Matlab program. The calculated polymorphic concentrations governed the control of cooling and reheating cycles of the crystallization using a programmable logic controller. The developed control approach was successfully adapted for the production of both pure polymorphic forms such as the kinetically preferred Form II or thermodynamically stable Form I.

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