Plasticizers Increase Adhesion of the Deteriogenic Fungus Aureobasidium pullulans to Polyvinyl Chloride

Abstract

Initial adhesion of fungi to plasticized polyvinyl chloride (pPVC) may determine subsequent colonization and biodeterioration processes. The deteriogenic fungus Aureobasidium pullulans was used to investigate the physicochemical nature of adhesion to both unplasticized PVC (uPVC) and pPVC containing the plasticizers dioctyl phthalate (DOP) and dioctyl adipate (DOA). A quantitative adhesion assay using image analysis identified fundamental differences in the mechanism of adhesion of A. pullulans blastospores to these substrata. Adhesion to pPVC was greater than that to uPVC by a maximum of 280% after a 4-h incubation with 108 blastospores ml−1. That plasticizers enhance adhesion to PVC was confirmed by incorporating a dispersion of both DOA and DOP into the blastospore suspension. Adhesion to uPVC was increased by up to 308% in the presence of the dispersed plasticizers. Hydrophobic interactions were found to dominate adhesion to uPVC because (i) a strong positive correlation was observed between substratum hydrophobicity (measured by using a dynamic contact angle analyzer) and adhesion to a range of unplasticized polymers including uPVC, and (ii) neither the pH nor the electrolyte concentration of the suspension buffer, both of which influence electrostatic interactions, affected adhesion to uPVC. In contrast, adhesion to pPVC is principally controlled by electrostatic interactions. Enhanced adhesion to pPVC occurred despite a relative reduction of 13° in the water contact angle of pPVC compared to that of uPVC. Furthermore, adhesion to pPVC was strongly dependent on both the pH and electrolyte concentration of the suspension medium, reaching maximum levels at pH 8 and with an electrolyte concentration of 10 mM NaCl. Plasticization with DOP and DOA therefore increases adhesion ofA. pullulans blastospores to pPVC through an interaction mediated by electrostatic forces.

Influence of starvation, surface attachment and biofilm growth on the biocide susceptibility of the biodeteriogenic yeast Aureobasidium pullulans

“…These cells were formed as an LDM after a quick spin down on the bottom of the wells and had no time to attach. Adhesion and attachment of A. pullulans YL cells is initiated after deposition on a plastic surface, but previous studies in our lab have shown that c. 75% of the deposited cells were attached within 2 h and a maximum was reached after 4 h of incubation (Webb et al 1999). Starvation for 48 h decreased the susceptibility of A. pullulans YL cells to both OIT and NaOCl irrespective of whether they were starved in suspension for 48 h and settled immediately before challenge, or were starved attached for 48 h to the plastic bottom of the wells and then challenged.…”

“…More importantly, A. pullulans has recently been found to be the major colonizer and deteriogen of plasticized polyvinylchloride [pPVC, a polyvinylchloride with added plasticizers bis-(2-ethylhexyl adipate) and bis-(2-ethylhexyl phtalate) up to 50% of the weight] in the outdoor environment (Webb et al 2000). It is able to switch from the YL to the mycelial phase and grow on pPVC with adhesion to the plastic surface greatly facilitated by the presence of plasticizers (Webb et al 1999). As outdoor-exposed pPVC is frequently protected through the incorporation of biocides, the need to study the biocide susceptibility of A. pullulans has led to the development of a real-time green fluorescent protein (GFP) assay of the fungal antimicrobial susceptibility in suspension measuring the loss of fluorescence as an indicator of cell death (Webb et al 2001).…”

Bacterial adhesion to diamond‐like carbon as compared to stainless steel

“…Using a radial flow chamber with shear rates of 50, 200, 500, and 2000 s 21 , Katsikogianni et al 19 have recently shown that adhesion of two slime producing S. epidermidis strains on polyvinyl chloride (PVC) can be reduced by application of a DLC coating. Probably, this reduction in staphylococcal adhesion is a result of the decrease in substratum hydrophobicity, [20][21][22][23] PVC having a water contact angle of around 105 degrees compared to 87 degrees for DLC-coated PVC. Jones et al 24 have had similar results, showing that more hydrophilic, DLC-coated polyurethanes were subject to significantly less bacterial encrustation and adhesion than more hydrophobic, uncoated polyurethane.…”

Plasticization effect of lignin in some highly filled vinyl formulations

“…Webb et al [4] showed that plasticization with DOP and dioctyl adipate increases adhesion of one of the omnipresent fungi within the environment, Aureobasidium pullulans, to plasticized PVC and stimulates its biodegradation.…”