Enhanced degradation of phototreated recycled and unused low-density polyethylene films by Pleurotus ostreatus.

ABSTRACT

Polyethylene, one of the most used petroleum-derived polymers, causes serious environmental pollution. The ability of Pleurotus ostreatus to degrade UV-treated and untreated recycled and unused (new) low-density polyethylene (LDPE) films was studied. We determined the fungal biomass production, enzyme production, and enzyme yield. Changes in the chemical structure and surface morphology of the LDPE after fungal growth were analyzed using FTIR spectroscopy and SEM. Functional group indices and contact angles were also evaluated. In general, the highest Lac (6013 U/L), LiP (2432 U/L), MnP (995 U/L) and UP (6671 U/L) activities were observed in irradiated recycled LDPE (IrRPE). The contact angle of all samples was negatively correlated with fermentation time; the smaller the contact angle, the longer the fermentation time, indicating effective biodegradation. The IrRPE samples exhibited the smallest contact angle (49°) at 4 weeks, and the samples were fragmented (into two pieces) at 5 weeks. This fungus could degrade unused (new) LDPE significantly within 6 weeks. The biodegradation of LDPE proceeded faster in recycled than in unused samples, which can be enhanced by exposing LDPE to UV radiation. Enzymatic production during fungal growth suggest that LDPE degradation is initiated by laccase (Lac) followed by lignin peroxidase (LiP), whereas manganese peroxidase (MnP) and unspecific peroxygenase (UP) are involved in the final degradation process. This is the first experimental study on the fungal growth and its main enzymes involved in LDPE biodegradation. This fungus has great promise as a safe, efficient, and environmentally friendly organism capable of degrading LDPE.