Modelling diffusivity in porous polymeric membranes with an intermediate layer containing microbial cells

Three-layer systems (membrane – composite layer (cells + polymer) – membrane) are important in different biochemical applications. Models of latex layered-membranes were evaluated and compared with experimental data in order to predict the diffusivity of substrates in the composite layer containing living E.coli microbial cells. Diffusivity predictions are dependent on the presence or the absence of a ‘skin’ layer, on the degree of polymer particle coalescence and on the thickness of each layer. Simulations with layered models were made to identify the dominant mechanisms in the three-layer system. It was found that the layered system is sensitive to the latex coatings porosity when the composite layer occupies less than 50% of the total membrane system thickness. Whenever the control of polymer particle coalescence and of the layers (coating/composite layer) thickness may be achieved, multi-layer systems presenting a wide range of relative diffusion conductivities may be built for different types of living cells and for a wide variety of practical applications. The diffusivity of the latex layer is proportional to the square of latex porosity.