The Effect of Surface Hydrophobicity on the Attachment of Fungal Conidia to Substrates of Polyvinyl Acetate and Polyvinyl Alcohol

Abstract

AbstractBiofouling of PVAc and PVOH surfaces by fungal conidia can result in surface discolouration and subsequent biodeterioration. In order to understand the interactions of fungal conidia on polymer surfaces, the surface properties of PVAc and PVOH and the hydrophobicity, size and shape of three type of fungal conidia was determined (Aspergillus niger 1957, Aspergillus niger 1988 and Aureobasidium pullulans). Fungal conidia were used in a range of binding assays (attachment, adhesion and retention). The PVAc and PVOH demonstrated different surface topographies and the PVAc demonstrated a higher maximum height (300.6 nm) when compared to the PVOH (434.2 nm). The PVAc surfaces was less wettable (75°) than the PVOH surface (62°). The FTIR demonstrated differences in the chemistries of the two surfaces, whereby the PVOH confirmed the presence of polar moieties. Hydrophobicity assays demonstrated that both A. niger species’ were more non-wettable than the A. pullulans. Following the attachment assays, the more hydrophobic Aspergillus spp. conidia attached in greater numbers to the more wettable surface and the A. pullulans was retained in greater numbers to the less wettable PVAc surface. The adhesion and retention assays demonstrated that the more polar surface retained all the types of conidia, regardless of their surface hydrophobicities. This study demonstrated that conidial binding to the surfaces were influenced by the chemistry and physicochemistry of the surfaces and spores. However, the inclusion of a washing stage influenced the adhesion of conidia to surfaces. In environments that were indicative of a attachment or retention assay a PVAc surface would reduce the number of A. niger spp. spores whilst a PVOH surface would reduce the number of A. pullulans spores. However, in an environment similar to a adhesion assay, a PVAc surface would be most beneficial to reduce spore retention. Thus, the use of the correct methodology that reflects the environment in which the surface is to be used is important in order to accurately inform hygienic surface development.