Low-Density Polyethylene Film Biodegradation Potential by Fungal Species from Thailand

Abstract

Accumulated plastic waste in the environment is a serious problem that poses an ecological threat. Plastic waste has been reduced by initiating and applying different alternative methods from several perspectives, including fungal treatment. Biodegradation of 30 fungi from Thailand were screened in mineral salt medium agar containing low-density polyethylene (LDPE) films. Diaporthe italiana, Thyrostroma jaczewskii, Collectotrichum fructicola, and Stagonosporopsis citrulli were found to grow significantly by culturing with LDPE film as the only sole carbon source compared to those obtained from Aspergillus niger. These fungi were further cultured in mineral salt medium broth containing LDPE film as the sole carbon source for 90 days. The biodegradation ability of these fungi was evaluated from the amount of CO2 and enzyme production. Different amounts of CO2 were released from D. italiana, T. jaczewskii, C. fructicola, S. citrulli, and A. niger culturing with LDPE film, ranging from 0.45 to 1.45, 0.36 to 1.22, 0.45 to 1.45, 0.33 to 1.26, and 0.37 to 1.27 g/L, respectively. These fungi were able to secrete a large amount of laccase enzyme compared to manganese peroxidase, and lignin peroxidase enzymes detected under the same conditions. The degradation of LDPE films by culturing with these fungi was further determined. LDPE films cultured with D. italiana, T. jaczewskii, C. fructicola, S. citrulli, and A. niger showed weight loss of 43.90%, 46.34%, 48.78%, 45.12%, and 28.78%, respectively. The tensile strength of LDPE films cultured with D. italiana, T. jaczewskii, C. fructicola, S. citrulli, and A. niger also reduced significantly by 1.56, 1.78, 0.43, 1.86, and 3.34 MPa, respectively. The results from Fourier transform infrared spectroscopy (FTIR) reveal an increasing carbonyl index in LDPE films culturing with these fungi, especially C. fructicola. Analysis of LDPE films using scanning electron microscopy (SEM) confirmed the biodegradation by the presence of morphological changes such as cracks, scions, and holes on the surface of the film. The volatile organic compounds (VOCs) emitted from LDPE films cultured with these fungi were analyzed by gas chromatography-mass spectrometry (GC-MS). VOCs such as 1,3-dimethoxy-benzene, 1,3-dimethoxy-5-(1-methylethyl)-benzene, and 1,1-dimethoxy-decane were detected among these fungi. Overall, these fungi have the ability to break down and consume the LDPE film. The fungus C. fructicola is a promising resource for the biodegradation of LDPE which may be further applied in plastic degradation systems based on fungi.

A Review of the Fungi That Degrade Plastic

“…Plastic degraders in the Dothideomycetes have the ability to degrade LDPE, PUR, PS, PCL, PEA, PPA, PBA, HDPE, PVC, PE, PU, and Sky-Green plastics ( Table 2 ). Recent studies on plastic-degrading members of the Dothideomycetes are those of Khruengsai et al [ 64 ] and Brunner et al [ 6 ]. In the phylogenetic tree, the Dothideomycetes formed a well-supported clade sister to the Arthoniomycetes.…”

“…The plastic types they are reported to degrade are HDPE, LDPE, PCL, PE, PVC, PS-PUR, PEA, PPA, PBA, PHB, Poly[3HB-co-(10 mol%) 3HV], Sky-Green, PHV, PBS, PLA and PVC ( Table 2 ). Recent studies on plastic-degrading Eurotiomycetes are those of Rani & Singh [ 12 ], Ndahebwa Muhonja et al [ 54 ], Bermúdez-García et al [ 57 ], Laila [ 63 ], Khruengsai et al [ 64 ], Munir et al [ 65 ], Alshehrei [ 69 ], Sangale et al [ 2 ], Duan et al [ 90 ], El-Morsy et al [ 92 ], Brunner et al [ 6 ] and Ojha et al [ 26 ]. The Eurotiomycetes is the uppermost clade within our phylogram ( Figure 1 and Figure 2 ).…”

“…The plastic types they are reported to degrade are PE, PS, PHB, Poly[3HB-co-(10 mol%) 3HV], PUR, PS-PUR, HDPE, LDPE, PVC, PCL, PEA, PPA, and PBA ( Table 2 ). Recent studies of plastic-degrading Sordariomycetes are those of Munir et al [ 65 ], (Yang et al [ 93 ], Brunner et al [ 6 ], and Khruengsai et al [ 64 ]. The Sordariomycetes formed a middle clade within the main Ascomycota clade that is sister to the Laboulbeniomycetes ( Figure 1 and Figure 2 ).…”

Biodeterioration of low-density polyethylene by mangrove-associated endolichenic fungi and their enzymatic regimes

“…2019) and Thyrostroma jaczewskii , Stagonosporopsis citrulli , Aspergillus niger , Diaporthe italiana and Coolectotrichum fructicola showed percent weight losses ranging from 7·32 to 17·07% (Khruengsai et al . 2021). The degree of water absorption by ELF‐treated LDPE strips is also shown in Table 1.…”

“…The abilities of fungi in reducing tensile strength, were comparable with the previous studies on fungal‐mediated LDPE biodegradation, where 2·99–23·21% reduction range was reported by Khruengsai et al . (2021).…”