Effect of hydrophobicity of polymer materials used for water purification membranes on biofilm formation dynamics

Abstract

We characterized the dynamics of biofilm formation on various polymer surfaces used in the preparation of water purification membranes by using a flow cell incubation apparatus and confocal laser scanning microscopic observation. Flat films with different surface hydrophobicity were fabricated from eight kinds of polymers used for microfiltration and ultrafiltration membranes. Pseudomonas putida NBRC 100650 was used as a model strain. Firstly, the bacterial adhesion property of each polymer surface was examined by an immersion test in bacterial suspension. Bacterial adhesion increased with increasing hydrophobicity of polymer surfaces. Then, the dynamics of biofilm formation were characterized by time courses of the bacterial amounts on each polymer surface using a flow cell incubation apparatus. Uniform, flat, and thin biofilms were rapidly formed on the hydrophobic surface of polyvinylidenefluoride (PVDF). In contrast, the hydrophilic surface of polyvinyl alcohol (PVA) prevented bacterial adhesion and biofilm formation; however, localized rough and thick biofilms were formed at 200h of long-term incubation. On polyethersulfone, which had intermediate hydrophobicity between PVDF and PVA, rough and thick biofilms were observed at 68h, and their thickness and coverage increased with incubation time. The hydrophobicity of the polymer surfaces significantly affected the dynamics and structure of biofilm formation.