Ca-alginate hydrogel rheological changes caused by yeast cell growth dynamics

Interactions between immobilized cell populations and polymer matrixes in the form of hydrogel within micro-beads have complex restrictive action on cell growth dynamics. The forces generated by cell growth and interactions between solvent, network parts and cells influenced this process. It induces structural changes of hydrogel which has the feedback action on cell growth. Rheological response of hydrogel includes both the reversible deformation of domains, as well as the domains partially disintegration which cause permanent irreversible deformation. Estimation of the relationship between cell dynamic environment and cell function offers the possibility for the optimization of various biotechnological processes. The growth of yeast cells within Ca-alginate hydrogel matrix is used as model system for considering such complex phenomena. Structural changes of Ca-alginate hydrogel is modelled using modified general Zener constitutive equation with fractional derivatives. It is suitable for incorporating irreversible effects on macroscopic level. However, the additional consideration of the dynamics of structural changes of Ca-alginate network on mesoscopic level offers the deeper insight into the irreversible nature of deformation caused by cellular local mechanical action. The particular form of free energy functional on mesoscopic level describes various kinds of interactions, which affected the dynamics of cell growth and cause pseudo-phase transition of hydrogel.