Bienzymatic modification of polymeric membranes to mitigate biofouling

Abstract

Staphylococcus aureus and Staphylococcus epidermidis are considered as major human pathogens and their resistance to antibiotic treatment and host defense systems can be increased due to the formation of biofilms. The biofilm-associated biofouling of industrial surfaces, particularly membranes, remains a serious concern that challenges investigators to develop practical solutions for the reduction of their impact. The present study developed antibacterial membrane surfaces that can mitigate biofilm formation. α-Amylase and lysozyme, as antibacterial enzymes, were covalently immobilized on polydopamine/cyanuric chloride functionalized polyethersulfone (PES) membranes to form biocompatible antibacterial surfaces. Several methods including SEM, AFM, Bradford, water contact angle goniometry, and surface free energy measurement techniques have been used to demonstrate the attachment of enzymes onto PES membranes by changing the physicochemical properties of the surface. The two enzymatic systems alter the membrane surface chemistry by rendering lower free surface energy and higher hydrophilicity, which leads to the creation of a layer of hydration energy barrier preventing microorganisms from being anchored on the surface. Those microorganisms that managed to overcome the energy barrier and get attached to the surface are attached by the enzymes' bond cleavage functionality. This multilevel defense system protects the membrane against any biofilm formation. The results of microtiter test and flow cytometry assay indicated that α-amylase/lysozyme mixture treated membrane samples came with more than 87% removal of biofilms. The results of the biofouling experiment in a dead-end cell demonstrated that the modified membrane surface had only a slightly impaired water flow compared to an unmodified membrane, which was due to the removal of biofilms by the enzymes’ activity. The results also showed that the modification of membranes with antibacterial enzymes could create a new biotechnological horizon to prevent biofilm formation. © 2019 Elsevier B.V.