This project concerns the study of the behaviour of microbial populations subjected to controlled variations in their environment and induced responses. It combines numerical (TBI-IMT) and experimental (TBI-LGC) approaches supported by 2 doctoral theses conducted in parallel. It involves: An experimental strategy for immobilizing microorganisms within a reactor in order to study the links between biological activity and transfers. The work carried out will make it possible to quantify the limits of intensification of biological processes, in particular the concentration of catalytic biomass and to understand the links between biological reactivity and transfer phenomena in dense medium with low water content. The aim of the project is to design highly productive microbial processes that contribute to the environmental transition challenges brought about by biotechnology. The development of a tool for predictive simulation of bioreactors integrating microbial dynamics via population balances, integrating extrinsic factors (concentration, temperature, pH) and intrinsic factors (cell division). The work will focus on the improvement of biophysical models (active membrane transfers, partition functions) based on the analysis of existing experimental data.