Method for obtaining cell metabolites with a microfluidic bioreactor consisting of - at least two modules (2, 3, 4, 5, 6, X) each having a cavity that is subdivided by a membrane into a cell chamber (211, 311, 411) for receiving cells and a material chamber (221, 321, 421) through which a liquid solution that has at least one additive and cell metabolites can flow, with each membrane comprising a reaction region in which the membrane is at least partly permeable for the solution that has at least one additive and the cell metabolites, and - a fluid conducting system for the liquid solution that has the at least one additive and the cell metabolites, and which connects said material chamber (221, 321, 421) in series and/or parallel with one another - and means for unidirectional flow through the fluid conducting system. with the method steps: a) introducing cells into the cell chamber (211, 311, 411) b) creating a liquid flow of a liquid solution that has at least one additive in the fluid conducting system of the microfluidic bioreactor for the synthesis of the at least one cell metabolite, with the liquid solution that has the at least one additive flowing through at least two modules in succession and in the process penetrating the cell chamber (211, 311, 411) via the material chambers (221, 321, 421) through the membrane, then in the cell chamber (211, 311, 411) synthesising at least one product with the cells, and with the liquid solution that has the at least one additive and the at least one product being returned through the membrane via the material chambers (221, 321, 421) into the fluid conducting system, with the product of the module through which the solution previously flowed being the educt of the subsequent module, until the product is the cell metabolite c) removing the at least one cell metabolite from the liquid flow. - at least two modules (2, 3, 4, 5, 6, X) each having a cavity that is subdivided by a membrane into a cell chamber (211, 311, 411) for receiving cells and a material chamber (221, 321, 421) through which a liquid solution that has at least one additive and cell metabolites can flow, with each membrane comprising a reaction region in which the membrane is at least partly permeable for the solution that has at least one additive and the cell metabolites, and - a fluid conducting system for the liquid solution that has the at least one additive and the cell metabolites, and which connects said material chamber (221, 321, 421) in series and/or parallel with one another - and means for unidirectional flow through the fluid conducting system. a) introducing cells into the cell chamber (211, 311, 411) b) creating a liquid flow of a liquid solution that has at least one additive in the fluid conducting system of the microfluidic bioreactor for the synthesis of the at least one cell metabolite, with the liquid solution that has the at least one additive flowing through at least two modules in succession and in the process penetrating the cell chamber (211, 311, 411) via the material chambers (221, 321, 421) through the membrane, then in the cell chamber (211, 311, 411) synthesising at least one product with the cells, and with the liquid solution that has the at least one additive and the at least one product being returned through the membrane via the material chambers (221, 321, 421) into the fluid conducting system, with the product of the module through which the solution previously flowed being the educt of the subsequent module, until the product is the cell metabolite c) removing the at least one cell metabolite from the liquid flow.