As important enzyme leaching was observed on the electrostatically immobilized TAs, post-treatment strategies of the electrostatically immobilized TAs were applied to improve TA anchoring at the functionalized PAN membrane surface. Among the developed strategies, the covalent binding of TAs and of the PEI layer using glutaraldehyde (GA) gave the most satisfying results (high specific activity, minor leaching). On the other hand, the TA covalent grafting on functionalized PP membranes yielded even more efficient biocatalysts (higher specific activity) displaying enhanced robustness (no leaching) and full recyclability.