Inhibition of Agrobacterium tumefaciens biofilm formation by acylase I-immobilized polymer surface grafting of a zwitterionic group-containing polymer brush

Membrane processes for water purification and wastewater treatment are impacted by biofilm formation, a hotspot for bacterial cell-cell communication, mainly mediated by N-acyl homoserine lactones (AHLs) as signal compounds. Polymer materials for membrane filtration require high water permeability and biofilm deterrents. Therefore, in this study, a hydrophilic and enzyme-immobilizing polymer membrane was designed, for the first time, to prevent biofilm formation by degrading AHLs. A polyethylene membrane (PE) sheet was grafted as a substratum with glycidyl methacrylate (GMA) by radiation-induced graft polymerization (RIGP). The epoxy group in GMA was further converted into dimethylamino-gamma-butyric acid (DMGABA) to increase hydrophilicity. To prevent biofilm formation by cell-cell communication, the quorum-quenching enzyme, acylase I, with or without activity was immobilized onto a DMGABA membrane sheet, providing enzymatically active DMGABA (EI-DMGABA) and inactive DMGABA (Ina-EI-DMGABA) sheets, respectively. The introduction of DMGABA improved hydrophilicity with a static contact angle of 30.2 degrees, as compared to GMA (84.3 degrees). In a flow cell biofilm formation experiment, biofilm formation of Agrobacterium tumefaciens, using AHLs for quorum sensing, was dramatically inhibited on an EI-DMGABA sheet, but not on an Ina-EI-DMGABA sheet. The successful result to prove the concept of active AHL-degrading enzyme immobilized onto a hydrophilic polymer surface likely paves the way for the application to inhibition of unfavorable biofilm formation onto an interface.