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

Abstract

Plasticized polyvinyl chloride (pPVC) with or without incorporated biocides was buried in grassland and forest soil for up to 10 months. The change with time in viable counts of fungi on the plastic surface was followed, together with the percentage capable of clearing the two plasticizers dioctyl adipate (DOA) and dioctyl phthalate (DOP). With time fungal total viable counts (TVC) on control pPVC increased and the fraction able to clear DOA was considerably higher than the average estimated in both soil types. A total of 92 fungal morphotypes were isolated from grassland soil and 42 from forest soil with the greatest variety of fungal isolates observed on control pPVC. The incorporation of biocides into pPVC affected both fungal TVC and the richness of species isolated. The biocides NCMP [n-(trichloromethylthio)phthalimide], OBPA (10,109-oxybisphenoxarsine) and OIT (2-n-octyl-4-isothiazolin-3-one) were the most effective in grassland soil, and TCMP [2,3,5,6-tetrachloro-4-(methylsulphonyl)pyridine] and NCMP the most effective in forest soil. In grassland soil, Penicillium janthinellum established as a principal colonizer and was recovered from all pPVC types. DOP clearers were found at much lower levels than DOA clearers, with Doratomyces spp. being the most efficient. At the end of 10 months the physical properties of the pPVC were altered; changes in stiffness were the most significant for heavily colonized grassland-buried pPVC samples, whereas in forest soil, the extensibility of the pPVC was affected more than the stiffness. These results suggest that fungi are important colonizers of pPVC buried in soil and that enrichment of soil fungi capable of clearing DOA occurs during colonization of the plastic surface. The results also demonstrate that incorporated biocides have a marked impact on the richness of species colonizing the pPVC surface.

Fungal Communities Associated with Degradation of Polyester Polyurethane in Soil

“…were the dominant cultivable fungi on PU buried in the acidic soil. G. pannorum was the dominant fungus in plasticized polyvinyl chloride (pPVC) degradation in a laboratory microcosm (5), and it was also important in pPVC degradation in Bulgarian grassland soil (32). This fungus may therefore prove to be important for plastic waste remediation in the future.…”

“…1). Soil conditions influence the composition of fungal communities on the surface of buried pPVC, and in forest soil, pPVC supported a different range of fungi compared to pPVC in grassland soil (32). Also, changing the water-holding capacity within the same soil also altered the fungal communities on buried PU (5).…”

“…PU is used in a variety of industrial applications, including insulating foams, fibers, and synthetic leather and rubber goods. The presence of ester and urethane linkages in the backbone of PUs makes them susceptible to hydrolysis by enzymes secreted by microorganisms, releasing breakdown products which may act as a carbon source and lead to a weakening of the tensile strength (1,13,22,26,27).Both PU-degrading fungi (5,6,12,32) and bacteria (1, 20, 23) have been isolated from PU, indicating that there are potential reservoirs of PU-degrading organisms widespread in the environment. It is known that fungi and not bacteria are predominantly responsible for PU degradation in laboratory soil microcosms (5), although studies are lacking on the ecology of PU colonization and degradation in situ by fungi in the soil.…”

“…Both PU-degrading fungi (5,6,12,32) and bacteria (1,20,23) have been isolated from PU, indicating that there are potential reservoirs of PU-degrading organisms widespread in the environment. It is known that fungi and not bacteria are predominantly responsible for PU degradation in laboratory soil microcosms (5), although studies are lacking on the ecology of PU colonization and degradation in situ by fungi in the soil.…”

“…Plastics vulnerable to biodegradation include the polyhydroxyalkanoates, polycaprolactone, polylactic acid, polyvinyl chloride (31,32), and polyester polyurethane (PU). PU is used in a variety of industrial applications, including insulating foams, fibers, and synthetic leather and rubber goods.…”