Isolation and molecular characterization of low density polythene degrading fungi from soils of Bhanpur dumping zone with reference to screening of enzymes responsible for biodegradation

Abstract

Low density Polyethylene (LDPE) in various forms has become a part of life. Its accretion due to non degradable nature is concern, endangering life on earth. Amongst various methods of LDPE disposal bioremediation is regarded as ecofriendly and widely accepted. The current investigation was an attempt to isolate potent PE degrading fungus from municipal landfill soils of Bhopal, India loaded with plastic waste.16 fungal isolates were recorded from the site; PE deteriorating fungus was screened using mineral salt agar medium amended with 3% LDPE powder as sole carbon source. The isolate Penicillium citrinum, Aspergillus flavus, Aspergillus fumigatus and Aspergillus nidulans showed fast fungal colony growth in screening medium was selected for biodegradation study. P.citrinum showed 38.82± 1.08% weight loss of untreated LDPE pieces followed by Aspergillus fumigatus, Aspergillus flavus and Aspergillus nidulans respectively. To improve the degradation capacity nitric acid and UV pretreatment was performed; biodegradation was significantly stimulated after pretreatment. Laccase, lipase, esterase and manganese peroxidase activities were assayed by spectrophotometer. LDPE biodegradation was analyzed by weight loss %, change in pH during fungal growth, field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). FTIR spectra showed appearance of new functional groups assigned to hydrocarbon biodegradation, confirming enzymatic role in process. Changes in FTIR spectra of LDPE samples (untreated and pretreated) before and after biodegradation and surface changes in the biodegraded LDPE (indicated from FE-SEM) confirmed depolymerization of LDPE in all the fungal treated samples. Further changes in thermal decomposition rates of biodegraded samples in comparison to control, validate biodegradation. This is the first report signifying high competence of P.citrinum in LDPE degradation without prior pretreatment. newline