Effect of hydrogen peroxide as an inducing agent of peroxidase enzymes for the polyethylene biodegradation by Pleurotus ostreatus in liquid fermentation

Widely used petroleum-derived polymers, such as polyethylene (PE), are a significant source of environmental pollution due to their accumulation in the ecosystem. In the present study, P. ostreatus was grown in a PE-supplemented medium added with H2O2 as a peroxidase enzymeinducing agent for 5 weeks in liquid fermentation to evaluate the biodegradation of this polymer. A medium lacking H2O2 was used as a control. Enzyme production by P. ostreatus and the contact angle of the PE surface were evaluated. Chemical structural changes of the PE surface were determined by FTIR spectroscopy. The activities of laccase, unspecific peroxigenase, and lignin peroxidase were found to be higher in the control medium (4072, 3692 and 4224 U/L, respectively) than in the medium supplemented with H2O2 (3531, 2910 and 2878 U/L, respectively). Changes in the chemical structure and the decrease in the contact angle of the PE surface showed biodegradation of the polymer. The PE surface of control cultures had a lower contact angle (60.9°) than that observed in PE of cultures added with H2O2 (66.8°). The addition of 5 mM of H2O2 to the medium increased the production of manganese peroxidase, however, it did not have a significant impact on the biodegradation of PE.