Biodegradation of synthetic plastics by the extracellular lipase of Aspergillus niger

Abstract

A rapid increase in plastic pollution is a major threat to the environment. One intriguing group of enzymes that can act as biocatalysts for the breakdown of polymers is lipase. This study reports the production of lipase from Aspergillus niger MG654699.1 utilizing agro-industrial residue (wheat bran) through solid-state fermentation. The produced lipase showed 176.55 U/mL of activity, 7.18 mg/mL of protein content, and 24.60 U/mg of specific activity under the optimal conditions of 37°C and pH 7.0. The biocatalytic activity of 30 KDa lipase resulted in 3.8%, 3.6%, and 5% weight loss of PE (polyethylene), PET (polyethylene terephthalate), and PS (polystyrene), respectively. Application of Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the lipase-mediated deterioration of treated polymer samples. The alterations in functional groups and surface structures of the samples showed the chemical and physical impact of the applied enzyme. The findings of this study showed that lipase can be employed as an eco-friendly and green biocatalyst for effective depolymerization and deterioration of environmental plastic waste.

Keywords

• Lipase
• Polyethylene
• Polyethylene terephthalate
• Polystyrene
• Biodegradation