Optimal process design space to ensure maximum viability and productivity in Penicillium chrysogenum pellets during fed-batch cultivations through morphological and physiological control

Abstract

Background: Biomass growth of Pencillium chrysogenum is characterised by a distinct pellet morphology consisting of compact hyphal agglomerates. Fungal pellets are advantageous in industrial process control due to rheological advantages but lead to biomass degradation due to diffusional limitations of oxygen and substrate in the pellet's core. Several fermentation parameters are known to affect key pellet characteristics regarding morphology, viability and productivity. Pellet morphology and size are affected by agitation. Biomass viability and productivity are tightly interlinked with substrate uptake and dissolved oxygen concentration. Results: The goal of this study was to study the impact of the fermentation parameters power input, dissolved oxygen content and specific substrate uptake rate on morphology, biomass viability and productivity. A design of experiments (DoE) approach was conducted and corresponding responses were analysed using novel morphological descriptors analysed by a previously established flow cytometry method. Results clearly display inverse correlations between power input and pellet size, specific morphological parameters related to pellet density can be increased in direct proportion to power input. Biomass viability and productivity are negatively affected by high specific substrate uptake rates. Conclusions: Based upon multiple linear regression, it was possible to obtain an optimal design space for enhanced viability and productivity at beneficial morphological conditions. We could maintain a high number of pellets with favourable morphology at a power input of 1500 W/m 3. A sound compromise between viability and high productivity is possible at a specific glucose uptake rate of 0.043 g/g/h at dissolved oxygen levels of 40% minimum.

A Chemometric Tool to Monitor and Predict Cell Viability in Filamentous Fungi Bioprocesses Using UV Chromatogram Fingerprints

“…This emphasizes that lower q s values help to sustain culture viability, as explained in our previous work: using a design of experiments (DoE) approach, we demonstrated the positive effect of lower qs setpoints in a reproducible manner [13].…”

“…Processes 2020, 8, x FOR PEER REVIEW 7 of 17 our previous work: using a design of experiments (DoE) approach, we demonstrated the positive effect of lower qs setpoints in a reproducible manner [13].…”

“…Reliable monitoring strategies capable of identifying the onset of a cultivation's decline phase are essential in order to avoid over-feeding and further decline of biomass viability. In this respect, the relationship between substrate availability and oxygen consumption is also a most relevant factor in process control: limiting substrate feeding regimes can positively affect productivity in secondary metabolite production while ensuring high viability due to less substrate oxidation and less oxygen consumption within the pellet [12,13].Spectroscopic and chromatographic data have been used in combination with statistical models for process monitoring strategies and quantifying process variables. Optical sensors have been widely used to measure and monitor different process variables, such as analyte concentration (e.g., product), product quality attributes (e.g., glycosylation) and cell level responses (e.g., cell sub-populations) [14][15][16][17].…”

“…Furthermore, the predictive power of the model was tested using partial least squares (PLS), orthogonal partial least squares (OPLS) and principal component regression (PCR). Based on the model results, the drop in cell viability was identified, and thereby used to define the optimal time point of harvest or measures to maintain high viability through process control; for instance, feeding profiles, power input and dissolved oxygen content [13].…”

“…Reliable monitoring strategies capable of identifying the onset of a cultivation's decline phase are essential in order to avoid over-feeding and further decline of biomass viability. In this respect, the relationship between substrate availability and oxygen consumption is also a most relevant factor in process control: limiting substrate feeding regimes can positively affect productivity in secondary metabolite production while ensuring high viability due to less substrate oxidation and less oxygen consumption within the pellet [12,13].…”