Enzyme immobilization is an important strategy to enhance the stability and recoverability of enzymes and to facilitate separation of enzymes from reaction products.However,enzyme purification followed by separate chemical steps to allow immobilization on a solid support reduces efficiency and yield of active enzyme.Here we describe polypeptide constructs that spontaneously sell-assemble into nanofibrils with fused active enzyme subunits displayed on the amyloid fibril surface.We measure steady-state kinetic parameters for the appended enzymes in situ within fibrils,and compare these for the identical protein constructs in solution.Finally,we demonstrate that the fibrils can be recycled and re-used in functional assays both in conventional batch processes and in a continuous-flow-chemistry microreactor.