Kinetic Modeling and Numerical Simulation as Tools to Scale Microalgae Cell Membrane Permeabilization by Means of Pulsed Electric Fields (PEF) From Lab to Pilot Plants

Abstract

Pulsed Electric Fields (PEF) is a promising technology for the gentle and energy efficient disruption of microalgae cells such as Chlorella vulgaris. The technology is based on the exposure of cells to a high voltage electric field, which causes the permeabilization of the cell membrane. Due to the dependency of the effective treatment conditions on the specific design of the treatment chamber, it is difficult to compare data obtained in different chambers or at different scales, e.g., lab or pilot scale. This problem can be overcome by the help of numerical simulation since it enables the accessibility to the local treatment conditions (electric field strength, temperature, flow field) inside a treatment chamber. To date, no kinetic models for the cell membrane permeabilization of microalgae are available what makes it difficult to decide if and in what extent local treatment conditions have an impact on the permeabilization. Therefore, a kinetic model for the perforation of microalgae cells of the species Chlorella vulgaris was developed in the present work. The model describes the fraction of perforated cells as a function of the electric field strength, the temperature and the treatment time by using data which were obtained in a milliliter scale batchwise treatment chamber. Thereafter, the model was implemented in a CFD simulation of a pilot-scale continuous treatment chamber with colinear electrode arrangement. The numerical results were compared to experimental measurements of cell permeabilization in a similar continuous treatment chamber. The predicted values and the experimental data agree reasonably well what demonstrates the validity of the proposed model. Therefore, it can be applied to any possible treatment chamber geometry and can be used as a tool for scaling cell permeabilization of microalgae by means of PEF from lab to pilot scale. The present work provides the first contribution showing the applicability of kinetic modeling and numerical simulation for designing PEF processes for the purpose of biorefining microalgae biomass. This can help to develop new processes and to reduce the costs for the development of new treatment chamber designs.

Decay of Trichomes of Arthrospira platensis After Permeabilization Through Pulsed Electric Fields (PEFs) Causes the Release of Phycocyanin

“…This implies that full disintegration at electric field strengths below a critical value is not possible solely by extending the treatment time, which again is dependent on the treatment temperature. This result conforms with the results of our previous study, where similar plateaus were observed for the microalga Chlorella vulgaris (Knappert et al, 2020). Pataro et al (2011) also measured a similar behavior for the yeast Saccharomyces cerevisiae.…”

“…PEF treatments were performed in a prototype device designed in-house. The exact configuration is described elsewhere (Knappert et al, 2020). Voltage and electric current were directly measured in the treatment chamber by a 75-MHz high-voltage probe and a 100-MHz electric current probe, respectively.…”

“…PI, a substance that cannot penetrate intact lipid membranes, was used as a dye. This substance has already been used as a dye to detect cell disintegration of phototrophic microorganisms (Luengo et al, 2014;Knappert et al, 2020). For the development of the method, heatinactivated cells were used (80 • C, 15 min) to minimize pigment interference with PI.…”

“…Concerning the treatment of A. platensis with PEF, several studies have shown that the technology is, in principle, suitable for permeabilizing the cell, thereby releasing compounds such as PC without extraction of water-insoluble components such as chlorophyll (Martínez et al, 2017;Jaeschke et al, 2019;Akaberi et al, 2020;Carullo et al, 2020;Käferböck et al, 2020). Even though flow cytometry and propidium iodide (PI) staining have been previously applied to detect the permeabilization of microalgae (Luengo et al, 2014;Knappert et al, 2020), they are not applicable to A. platensis because of the large size of the trichomes. Accordingly, the effect of PEFs on Arthrospira platensis was always determined indirectly in the cited studies by measuring the extraction kinetics for different molecules, i.e., PC, water-soluble proteins, or carbohydrates.…”

Opportunities of Hybrid Model-based Reinforcement Learning for Cell Therapy Manufacturing Process Control

“…Bioprocess Modeling and Analysis: In classic biomanufacturing literature, the bioprocess dynamics is usually modeled by mechanistic models in forms of ordinary/partial differential equations (ODEs/PDEs) (Mandenius et al, 2013). Because they are capable of representing the complex biochemistry of cells in a more complete way (Almquist et al, 2014), mechanistic models become popular and have been widely used in process optimization, design, control, and scale-up (Glen et al, 2018;Liu et al, 2013;Lu et al, 2015;Nfor et al, 2009;Knappert et al, 2020). However, for complex biomanufacturing operations, mechanistic models often oversimplify underlying process mechanisms and make a poor fit to real production data (Teixeira et al, 2007).…”