Fungi are the predominant micro-organisms responsible for degradation of soil-buried polyester polyurethane over a range of soil water holding capacities

Abstract

Aims: To investigate the relationship between soil water holding capacity (WHC) and biodegradation of polyester polyurethane (PU) and to quantify and identify the predominant degrading micro-organisms in the biofilms on plastic buried in soil. Methods and Results: High numbers of both fungi and bacteria were recovered from biofilms on soil-buried dumb-bell-shaped pieces of polyester PU after 44 days at 15-100% WHC. The tensile strength of the polyester PU was reduced by up to 60% over 20-80% soil WHC, but no reduction occurred at 15, 90 or 100% soil WHC. A PU agar clearance assay indicated that fungi, but not bacteria were, the major degrading organisms in the biofilms on polyester PU and 10-30% of all the isolated fungi were able to degrade polyester PU in this assay. A 5AE8S rDNA sequencing identified 13 strains of fungi representing the three major colony morphology types responsible for PU degradation. Sequence homology matches identified these strains as Nectria gliocladioides (five strains), Penicillium ochrochloron (one strain) and Geomyces pannorum (seven strains). Geomyces pannorum was the predominant organism in the biofilms comprising 22-100% of the viable polyester PU degrading fungi. Conclusions: Polyester PU degradation was optimum under a wide range of soil WHC and the predominant degrading organisms were fungi. Significance and Impact of the Study: By identifying the predominant degrading fungi in soil and studying the optimum WHC conditions for degradation of PU it allows us to better understand how plastics are broken down in the environment such as in landfill sites.

Biodegradative Activities of Selected Environmental Fungi on a Polyester Polyurethane Varnish and Polyether Polyurethane Foams

“…This material, however, is more recalcitrant to fungal attack than PS-PU (17). Although several works have documented the degradation of solid PS-PU by fungi (9)(10)(11)(12)(13)(14)17), scarce research on solid PE-PU biodegradation has been carried out. Early work reported that PE-PU foams were unaffected by Aspergillus niger and Cladosporium herbarum growth (18).…”

Fungal Communities Associated with the Biodegradation of Polyester Polyurethane Buried under Compost at Different Temperatures

“…Moisture content of soils has previously been found to have a marked influence on fungal growth and degradation of PU (15). The water-holding capacity was determined to be 71% and 40% for compost and soil, respectively, and the moisture content was ca.…”

“…To investigate fungal colonization of PU coupons following burial, total fungal viable counts and putative fungal PU degrader counts recovered from the surfaces of coupons were enumerated on compost extract agar (CEA) (15) and PUA plates, respectively (Fig. 4A).…”

“…Previously, fungi have been shown to be the dominant microorganisms involved in the biodegradation of polyester PU when buried in soil (15)(16)(17), and a number of fungal species that are capable of degrading PU have been isolated and identified (7,(15)(16)(17)(18)(19)(20). In this study, we investigated the potential of the composting process to deteriorate PU by comparing the rate of biodegradation when buried in compost at different temperatures representing the mesophilic and thermophilic stages.…”

Biodegradation of Synthetic Plastics

“…[ 16] Geomyces pannorum Nectria gliocladioides Penicillium ochrochloron [17] Bacillus subtilis [20] Pseudomonas chlororaphis [21] Alicycliphilus spp. [19] Polyethylene Brevibacillus borstelensis [36] Rhodococcus rubber [37] Penicillium simplicissimum YK [9] Brevibacillus borstelen [38] Penicillium frequentans Bacillus mycoides [10] Aspergillus niger Penicillium pinophilium [11] Penicillium pinophilium Aspergillus niger Cliocladium virens Penicillium chrysosporium [12] Bacillus sphericus Bacillus cereus [13] Streptomyces spp.…”