Fungal Colonization and Biodeterioration of Plasticized Polyvinyl Chloride

Abstract

Significant substratum damage can occur when plasticized PVC (pPVC) is colonized by microorganisms. We investigated microbial colonization of pPVC in an in situ, longitudinal study. Pieces of pPVC containing the plasticizers dioctyl phthalate and dioctyl adipate (DOA) were exposed to the atmosphere for up to 2 years. Fungal and bacterial populations were quantified, and colonizing fungi were identified by rRNA gene sequencing and morphological characteristics. Aureobasidium pullulans was the principal colonizing fungus, establishing itself on the pPVC between 25 and 40 weeks of exposure. A group of yeasts and yeast-like fungi, including Rhodotorula aurantiaca and Kluyveromyces spp., established themselves on the pPVC much later (after 80 weeks of exposure). Numerically, these organisms dominated A. pullulans after 95 weeks, with a mean viable count ؎ standard error of 1,000 ؎ 200 yeast CFU cm ؊2 , compared to 390 ؎ 50 A. pullulans CFU cm ؊2 . No bacterial colonization was observed. We also used in vitro tests to characterize the deteriogenic properties of fungi isolated from the pPVC. All strains of A. pullulans tested could grow with the intact pPVC formulation as the sole source of carbon, degrade the plasticizer DOA, produce extracellular esterase, and cause weight loss of the substratum during growth in vitro. In contrast, several yeast isolates could not grow on pPVC or degrade DOA. These results suggest that microbial succession may occur during the colonization of pPVC and that A. pullulans is critical to the establishment of a microbial community on pPVC.Plasticized PVC (pPVC) is highly susceptible to microbial attack in many different environmental situations. The problem was first identified in U.S. government reports of the deterioration of military equipment (8, 44), and subsequent reports described defacement and deterioration of commercial pPVC products (20,50). Biodeterioration of pPVC is now known to occur in a wide range of industrial, commercial, and structural applications (18,19,22).The susceptibility of pPVC results from the presence of plasticizers, commonly organic acid esters such as dioctyl phthalate (DOP) and dioctyl adipate (DOA), added to modify physical or mechanical properties of the polymer. Both bacteria (6,7,14) and fungi (5, 36) can degrade ester-based plasticizers. Loss of plasticizers from pPVC due to microbial degradation results in brittleness, shrinkage, and ultimately failure of the pPVC in its intended application.Microbial deterioration of pPVC has been studied extensively in vitro. Many studies have examined the resistance of pPVC formulations incorporating biocides to colonization by test organisms (38,39,46). Other research has determined biodegradability by measuring changes in the physical properties of pPVC, such as changes in tensile strength (49), mass (9), or electrical properties (42) during biodegradation. Several international standard test methods for microbiological susceptibility of plastics have been established (1, 2, 26).Colonization processes occurring...

Fungal colonization of soil-buried plasticized polyvinyl chloride (pPVC) and the impact of incorporated biocides

“…Sheets of pPVC were formulated as previously described (Webb et al, 2000). Biocide-containing pPVC was prepared by adding the biocides during plastic manufacture.…”

“…By contrast, there have been fewer studies focusing on the colonization of pPVC in situ (Upsher, 1984;Upsher & Roseblade, 1984;Webb et al, 2000). Although there is no convincing evidence that the polymer backbone of PVC can be degraded by micro-organisms (Andrady, 1994), incorporated plasticizers in pPVC have shown varying degrees of susceptibility to microbial degradation (Hamilton, 1983;Nalli et al, 2002;Roberts & Davidson, 1986;Webb et al, 2000). Of the plasticizers commonly incorporated into pPVC, phthalate plasticizers are of growing concern due to soil pollution leading to bioaccumulation and subsequent acute and chronic toxicity in microbes, plants and animals (Staples et al, 1997a, b).…”

Lipase degradation of plasticized polyvinyl chloride endotracheal tube surfaces to create nanoscale features

“…Fortunately, degradation of polymers such as pPVC by microbes is a well-known phenomenon and has been studied extensively. [13][14][15][16] Fungi have been shown to degrade esterbased plasticizers such as pPVC. 17 Biodegradation by fungi has been attributed to sn-1,3-specific lipases, such as the lipase found in Rhizopus arrhizus.…”

Disentangling identity of species of the genus Taphrina parasitizing herbaceous Rosaceae, with proposal of Taphrina gei-montani sp. nov.

“…Since no potential host plant was recorded at this locality, this sequence might represent the asexual, saprobic yeast state of T. gei-montani. It has been proven that the yeast states of Taphrina are adapted for survival outside host plant tissues in free environments and their presence in various organic and inorganic substrates was noted (Babjeva & Reshetova, 1998;Webb et al, 2000;In acio et al, 2004;Maksimova & Chernov, 2004;Wuczkowski et al, 2005;Yurkov et al, 2008;Jumpponen & Jones, 2009Fonseca & In acio, 2011;Cordier et al, 2012;Selbmann et al, 2014).…”