Monitoring Fungal Biodegradation of Low-density Polyethylene [LDPE] from Plastic Wastes Dump Sites Using FT-IR Spectra

Abstract

Introduction: Polyethylene is the most commonly used synthetic plastic and is poorly degraded in natural environments, thus causing serious environmental problems. Aim of the Study: This study was designed to investigate the polyethylene degrading potentials of fungal strains recovered from several plastic polluted sites. Place and Duration of Study: Department of Microbiology, Ekiti State University, Ado-Ekiti between January 2016 and October 2017. Methodology: Soil and buried water sachet samples were analysed for polyethylene degrading bacteria. Their abilities were monitored using dry weight, radial mycelial growth and Fourier transform infrared (FTIR) spectroscopy. Results: The Ekiti State Waste Management Board site had the highest number of fungi isolates [28.75 x 104 and 16 x 104 hyphal cells/propagules per ml] obtained from the soil and polyethylene waste samples respectively. Five of the nineteen fungal isolates utilised low density polyethylene [LDPE] and were identified via molecular techniques as Aspergillus flavus KMBF 1501, Penicillium simplicissimum YK 18, Alternaria alternata strain 20UPMNR, Aspergillus sp.  and an unknown isolate Ps. 10 which could not be identified due to its low amplicon size. The FT-IR spectra revealed a carbonyl absorption band in Aspergillus flavus KMBF 1501 and Penicillium simplicissium YK 18 degraded polyethylene powder with vibration [Vfh] of C=O at 1726.35 cm-1 normally observed at the frequency range of 1750 cm-1 – 1710 cm-1 denoting the formation of ketone or aldehyde group. A new Vfh of O-H stretch with H-bonded structure at 3286.81cm-1 was formed by the degrading ability of Aspergillus flavus KMBF 1501 suggesting the formation of a new functional group usually at frequency range of 3500 and 3200cm-1 as alcohol or phenol. A slight decrease in the Vfh of O-H bend from 931.65 cm-1 to 929.72 cm-1, indicating carboxylic acid was also observed. However, a slight increase in the Vfh of C=C stretch from 1635.69 cm-1 to 1639.55 cm-1 represent an alkene while its O-H stretch gave a carboxylic acid group with no significant change when compared to the control sample. Conclusion: The FT-IR analyses demonstrated the ability of the fungal isolates to colonise and modify LDPE films.