Modeling of microenvironmetal restricted yeast cell growth within Ca-alginate microbead

Aim. A phase-field mathematical model was formulated to describe yeast cell growth within the Ca-alginate microbead during air-lift bioreactor cultivation. Model development was based on experimentally obtained data for the intra-bead yeast cell volume fraction profile within the microbead after reaching the equilibrium state for cells (150 h), as well as, total yeast cell volume fraction per microbead and microbead volume as functions time. Microbead with growing yeast cells is treated as a two-phase system. one phase represents the cell agglomerates, while the other is the alginate hydrogel matrices. The interactions between phases are simulated using the Langevin class, non-conservative phasefield model based on the reduction of the modeling resolution. The model considered the growth of small domains of one phase (cell agglomerates) as nucleation. Methods. Total yeast cell volume fraction in the beads was estimated by using Thoma counting chamber after dissolution of beads. Local cell volume fraction per microbead layers is calculated from experimentally determined surface fraction of cells for various microbead cross sections by image analysis. Microbead volume is estimated by measuring the microbead diameter. Diameters of microbeads were measured using the optical microscope equipped with a micrometric device. Results. The proposed model offered the only one model parameter, which represents the specific measure of microenvironmental restrictive action to the cell growth dynamics. The optimal value of this model parameter is obtained by comparison analysis between experimental data and model predictions. Conclusion. Besides giving useful insights into the dynamics of restrictive cell growth within the Ca-alginate microbead, the model can be used as a tool to design/optimize the performance of microbead and studying the microenvironmental restrictive mechanism action of the cell growth