Cocoa agro-industrial residue (theobroma cacao) as inducer of the production of fungal laccase and kojic acid for application in the biodegradation of 17-α-ethinylestradiol

Abstract

Due to the ability to catalyze the oxidation of several substrates, the enzyme laccase has been used in several applications, among them the bioremediation of emerging pollutants. This work evaluate the capacity of the cocoa agro-industrial residue to induce the production of Pycnoporus sanguineus laccase and to apply the enzymatic extract in the biodegradation of 17-α-ethinylestradiol (EE2). The macro and micronutrient levels of the cocoa residue were previously evaluated to establish correlations with induction of enzymatic production. The fungus was cultured for 7 days at 28 °C and shaking at 150 rpm. For the biodegradation, the enzymatic extract of laccase was added to the solution of EE2 and the percentage of removal was evaluated. The production of enzyme extract was notably increased by the addition of only 1% (m v−1) of agro-industrial cocoa residue. Laccase activity reached 3920 U mL−1 on the 7th day of cultivation, being superior to the positive control (511 U mL−1). The percentage of EE2 removal was 63% after 4 h, and after 8 h of reaction the EE2 concentration was below the limit of detection (LOD, 0.35 µg mL−1). Analysis showed the presence of kojic acid in the enzyme extract, constituting a powerful redox mediator, capable of enhancing the action of laccase.