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

Abstract

Polyurethane (PU) is widely used in many aspects of modern life because of its versatility and resistance. However, PU waste disposal generates large problems, since it is slowly degraded, there are limited recycling processes, and its destruction may generate toxic compounds. In this work, we isolated fungal strains able to grow in mineral medium with a polyester PU (PS-PU; Impranil DLN) or a polyether PU (PE-PU; Poly Lack) varnish as the only carbon source. Of the eight best Impranil-degrading strains, the six best degraders belonged to the Cladosporium cladosporioides complex, including the species C. pseudocladosporioides, C. tenuissimum, C. asperulatum, and C. montecillanum, and the two others were identified as Aspergillus fumigatus and Penicillium chrysogenum. The best Impranil degrader, C. pseudocladosporioides strain T1.PL.1, degraded up to 87% after 14 days of incubation. Fourier transform infrared (FTIR) spectroscopy analysis of Impranil degradation by this strain showed a loss of carbonyl groups (1,729 cm ؊1 ) and NOH bonds (1,540 and 1,261 cm ؊1 ), and gas chromatography-mass spectrometry (GC-MS) analysis showed a decrease in ester compounds and increase in alcohols and hexane diisocyanate, indicating the hydrolysis of ester and urethane bonds. Extracellular esterase and low urease, but not protease activities were detected at 7 and 14 days of culture in Impranil. The best eight Impranil-degrading fungi were also able to degrade solid foams of the highly recalcitrant PE-PU type to different extents, with the highest levels generating up to 65% of dry-weight losses not previously reported. Scanning electron microscopy (SEM) analysis of fungus-treated foams showed melted and thinner cell wall structures than the non-fungus-treated ones, demonstrating fungal biodegradative action on PE-PU. IMPORTANCEPolyurethane waste disposal has become a serious problem. In this work, fungal strains able to efficiently degrade different types of polyurethanes are reported, and their biodegradative activity was studied by different experimental approaches. Varnish biodegradation analyses showed that fungi were able to break down the polymer in some of their precursors, offering the possibility that they may be recovered and used for new polyurethane synthesis. Also, the levels of degradation of solid polyether polyurethane foams reported in this work have never been observed previously. Isolation of efficient polyurethane-degrading microorganisms and delving into the mechanisms they used to degrade the polymer provide the basis for the development of biotechnological processes for polyurethane biodegradation and recycling. P olyurethane (PU), one of the most versatile polymers invented by humans, is synthesized from a wide variety of precursors generating almost infinite types of materials, from elastomers and varnishes to highly resistant components, such as automotive parts, foams, semirigid plastics, and textile fibers. Due to their versatility, PUs are widely used in different human activities as a substit...

Isolation and characterization of different promising fungi for biological waste management of polyurethanes

“…The strain involving the most significant weight loss on TPU is the strain of Penicillium section Lanata‐Divaricata. Isolated species of Penicillium have been described on PU degradation studies such as Penicillium chrysogenum (Alvarez‐Barragan et al ., ), but to the best of our knowledge, no isolated strains of Penicillium belonging to the section Lanata‐Divaricata has been reported to degrade PU. It is thus the first time for such a strain that a PU‐degrading activity is clearly demonstrated.…”

“…Degradation ability of the fungi thus depends on the bonds of the soft segment of the TPU but also on the macromolecular structure. Usually, additional carbon sources such as glucose (Matsumiya et al ., ; Khan et al ., ) or PDB (Alvarez‐Barragan et al ., ) are added to promote the microbial growth and thus, the biodegradation. Regarding the development of an efficient remediation or bio‐recycling process, working without additional carbon source such as glucose, as in our case, is a major financial gain.…”

“…Minimal medium preparation. Minimal medium (MM) was prepared according to Alvarez-Barragan et al, with some minor modifications (Alvarez- Barragan et al, 2016). Buffer with 19 mM of NaH 2 PO 4 and 33.5 mM of K 2 HPO 4 was supplemented by agar (15 g l À1 final) and HCl (1.8 mM final) and autoclaved at 121°C for 18 min.…”

“…Degradation of PU with filamentous fungi is described as more efficient than with bacteria due to outstanding enzymatic arsenals and abiotic features linked to filaments formation (Barratt et al ., ; Lucas et al ., ). Several types of PU materials such as polyether urethane foam (Alvarez‐Barragan et al ., ), thermoplastic polyester (Khan et al ., ) and PU waterborne dispersion of polyester PU (Russell et al ., ) have already been described as sensitive to fungal biodegradation.…”

Improving the Healthiness of Sustainable Construction: Example of Polyvinyl Chloride (PVC)

“…At the moment, many of the promising findings require specialized species and conditions for this [80]. Some have suggested that the white rot fungi might be able to biodegrade PVC [81].…”