A mathematical model was formulated to describe hybridoma cell growth within the alginate-poly-L-lysine (alginate-PLL) microcapsules during air-lift bioreactor cultivation. Model development was based on experimentally obtained data concerning the hybridoma cell counts, monoclonal antibody (mAb) production and the distribution of hybridoma cell growth within the microcapsules. The cell growth was modeled using a mean field approach expressed as Langevin class of equations for two different regions of alginate-PLL microcapsules, the alginate microcapsule core and the annular region between microcapsule core and membrane. In this paper we propose an influence of microenvironmental conditions on cell growth. The osmotic pressure changes in the Na-alginate liquefied annular region, as well as, the resistance effects of Ca-alginate hydrogel in the core region during the cell growth were incorporated into the model. Good agreement between the experimental data and model prediction values was obtained. The proposed model successfully predicted the impact of various microenvironmental restriction effects on the dynamics of cell growth and appears useful for further optimization of microcapsule design in order to achieve higher intra-capsule cell concentrations resulting in higher amounts of mAb produced. (c) 2006 Elsevier Ltd. All rights reserved.