Effect of Oxidation Treatment and UV Irradiation of Titanium Surface on Yeast Adhesion

Abstract

Abstract Support materials capable of immobilizing microorganisms, such as yeast, are important for developing bioreactors for producing useful substances and wastewater treatment. However, the intricacies of initial microorganism adhesion remain unclear owing to the complex interactions among physicochemical properties of the material and microbial cell surfaces. Therefore, this study was undertaken to elucidate the effects of changes in the physicochemical properties of oxidized titanium surfaces on yeast adhesion. Surface-oxidized titanium was selected as a biocompatible material anticipated to serve as a support material for yeast. The titanium surface properties were controlled through oxidation and UV irradiation treatments, and their effects on yeast adhesion were evaluated. The application of heat treatment or anodic oxidation to polished titanium led to a significant increase in the number of adherent yeast, particularly on the anodic-oxidized titanium surface. This observation suggests that anodic oxidation is the preferred method for enhancing yeast adhesion. Despite the known significance of surface hydrophilicity in microbial adhesion, no correlation was observed between hydrophilicity and yeast adhesion in this study. UV irradiation increased the surface free energy of oxidized titanium; however, the surface free energy of polished, heat-treated titanium when immersed in yeast extract-peptone-dextrose medium decreased owing to the adsorption of medium components. In contrast, anodic-oxidized titanium maintained its hydrophilicity and surface free energy after immersion, although it adsorbed more culture medium components than the other titanium samples. Surface characterization of the adsorption layer may provide a more comprehensive understanding of microbial adherence.