The maximum enzymatic activity obtained for the laccase produced by P. ostreatus was 888.41 IU/ml and for P. djamor 153.22 IU/ml. With these enzymatic extracts, it was possible to remove the dyes studied in the percentages reported in Table 1.

In figure 1, the UV-Vis spectra of the erionyl blue dye A-R are presented before and after the reaction. In this research using the P. ostreatus extract, it was possible to remove 93.77% of the dye erionyl blue A-R (Figure 2), classified as acid blue 260 with CAS number 62168-86-9 and molecular formula C₂₆H₂₃ClN₃NaO₆S, molecular mass of 563.96g / mol and belongs to the family of anthraquinones¹³.

Fig. 1: Spectrum of UV-Vis absorption of water artificially contaminated with erionyl blue A-R dye at 200 ppm and treated with Pleurotus ostreatus. A) Untreated water b) Treated water

Fig. 2: Erionyl Blue A-R

On the other hand, Sánchez-López¹⁴ demonstrated the ability of the enzyme extract (laccase and manganese peroxidase) from Trametes maxima strain MUCL 44155 to remove acid blue anthraquinone dye 62 by 91% measured at 630 nm. Other fungi such as Thanatephorus cucumeris have been used to degrade anthraquinone dyes as the blue reactive dye 5 by DyP peroxidase having percentages above 90% measured at 630 nm¹⁵. In Japan, Itoh et. al.¹⁶ have used the white rot fungus Coriolus versicolor to degrade violet dye 12 (4-dihydroxyanthraquinone).

The UV/Vis absorption spectra of the reaction products (Figure 1) showed an increase in absorbance from 520 nm and towards the ultraviolet region behavior very similar to those reported by Sánchez-López¹⁴ and Sugano¹⁵. With regard to the Pleurotus djamor strain, lower removal values were observed with respect to P. ostreatus (Table 1).
Table (1):
Percentage of removal of the studied dyes.

The solophenyl black dye (direct black 22) is classified as Index 35435, indicating that it is a polyazo dye. (17, 18) its structure is reported in figure 3. With respect to the oxidation of azo dyes like the solophenyl black FR by laccases and peroxidases, several authors report the formation of naphthoquinones^19-22. In contrast, Mohana et al²³ report that using a microbial consortium applied in the treatment of water contaminated with direct black 22 (solophenyl black), obtained as degradation products 1-naphthol and diphenylamine as a product of anaerobic reduction, similar results obtained by Chávez²⁴, but using microbial consortia isolated from the Alseseca River of the City of Puebla, Mexico, these products are toxic so it would be convenient to use oxidation mechanisms with laccases or peroxidases and not chemical reduction. Although the removal rates for this azo-type dye were low (Table 1), it is important to emphasize that in this case, the laccases of the strain Pleurotus djamor were more efficient than those of Pleurotus ostreatus. In addition, for wastewater treatment it is convenient to use a treatment train for the process to be efficient. It has been reported that ligninolytic enzymes produced by Basidiomycetes of the genus Trametes remove better the dyes of an anthraquinone nature than the azo^{25, 26}, as found in this research.

Fig. 3: Solophenyl Black FR

The partially purified enzyme had a molecular mass of 67 kDa as determined by polyacrylamide gel electrophoresis. It has been reported that most of these enzymes range from 50-70 kDa^{27, 28}.