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

Abstract

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.

Keywords: Agro-waste; Biocatalysis; Decolorization; Dyes; Ganoderma lucidum; Laccase.

Fig. 1

SDS-PAGE analysis of the Ganoderma lucidum E47 laccase. The band corresponding to the enzyme is signaled with a dashed arrow

Fig. 2

Effect of temperature on enzyme activity (white bars) and stability (gray bars)

Fig. 3

Effect of pH on enzyme activity (white bars) and stability (gray bars)

Fig. 4

Dye decolorization screening: biocatalyzed reaction (white bars) versus blank reaction without enzyme (gray bars)

Fig. 5

Reaction course plot for the decolorization of bromocresol green catalyzed by GLL (solid line, white circle markers) versus the blank reaction without enzyme (solid line, gray circle markers). Real-time pH plots are denoted with dashed lines with white or gray squares corresponding to the biocatalyzed reaction or the blank reaction without enzyme, respectively