From agro-waste to tool: biotechnological characterization and application of Ganoderma lucidum E47 laccase in dye decolorization.

The culture of fungal species from agro-waste allows for the sustainable preparation of valuable biotechnological products and contributes to establish the Circular Economy concept. The Ganoderma lucidum species is well known as producer of laccases (EC 1.10.3.2), which serves as a tool to oxidize chemicals. When producing G. lucidum E47 basidiomes with edible purposes out of rice crop residues, its laccase remains as by-product. In this work, we report the biotechnological characterization and application of the laccase recovered from spent cultures of the G. lucidum E47 strain. We detected at least one polypeptide (ca. 59 kDa) which displays attractive activity and stability values when used in the range of 18-45 °C in mildly acidic environment (pH 4.8-5.8). These parameters can be enhanced in the presence of organic cosolvents such as butyl acetate and methyl iso-butyl ketone, but the opposite effect is observed with solvents of lower log P. The best activity-stability performance is reached when the biocatalyst is used in pH 4.8 buffer with 5% (v/v) butyl acetate at 37 °C. The laccase was capable of decolorizing xanthene, azo and triarylmethane dyes, exhibiting excellent selectivity on bromocresol green and bromocresol purple. Furthermore, the biocatalyst displayed an attractive activity when assessed for the decolorization of bromocresol green in a proof-of-concept effluent biotreatment.