Identification of potential fungal degraders of low-density polyethylene (LDPE)

Low Density Polyethylene (LDPE) is one of the most important constituents of waste generated, since the time taken for its natural degradation is long. Therefore, this study mainly focused on identifying efficient fungal degraders of LDPE. Partially degraded polyethylene was collected from different places in Kaduwela area, Sri Lanka to isolate the abundant fungi in degrading polyethylene. For biodegradation studies, these fungal isolates were inoculated on streptomycin incorporated potato dextrose agar (PDA) medium which comprised 20-micron LDPE film. After 90 days of incubation, gravimetric analysis, light microscopy, Fourier- Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were conducted to determine the potent of these fungal isolates in degrading LDPE. These fungal isolates were identified by sequencing internal transcribed spacer region (ITS). Multiple alignments of partial sequences were performed by CLUSTAL W and the phylogeny was analyzed using MEGA 6.0 software. According to the one-way Analysis of Variance, the mean values of weight loss of control and Aspergillus niger isolate PS3. (P=0.000), control and Fusarium sp. isolate PS3 (P=0.031) and control and Penicillium sp. isolate PS2 (P=0.010) were significantly different. Scanning electron microscope images and light microscopic observations showed the presence of fungal colonization and surface erosion, cracks, folding and firm fungal attachment. The FTIR spectroscopy images of Fusarium sp. isolate PS3 treated LDPE films showed the early stage of degradation by initiating bonds such as carboxylic bonds and aldehyde bonds. The fungal isolates were identified as Fusarium sp. isolate PS3, Penicillium sp isolate PS2 and Aspergillus niger isolate PS3 by analyzing the ITS region sequencing. Therefore, it can be concluded that the fungal species, Fusarium sp., Aspergillus sp. and Penicillium sp. are capable of colonizing on LDPE films and has the potential to be developed into an inoculum for expedited LDPE degradation.