Decolorization of synthetic dyes by Stropharia rugosoannulata producing laccases as the main ligninolytic enzyme and their application.

With the rapid development of the textile and printing industries, dye pollution has emerged as an increasingly pressing concern. This study found that Stropharia rugosoannulata exhibits superior decolorization efficiency for various synthetic dyes, including azo dyes, anthraquinone dyes, and triphenylmethane dyes, compared to Pleurotus ostreatus, Lentinula edodes, and Hypsizygus marmoreus. S. rugosoannulata effectively decolorizes dyes in artificial textile effluents, with further enhancement observed upon the addition of metal ions (e.g., Mn²⁺, Cu²⁺, Fe²⁺) to the growth medium. Notably, S. rugosoannulata can degrade specific fabric dyes, such as remazol brilliant blue R (RBBR), acid red 73 (AR73), and a mixture of six dyes at 400 mg/L, achieving substantial degradation within 15 h. Mass spectrometry analysis revealed that two laccases, SrLAC1 (MDBSrug1_00049) and SrLAC9 (MDBSrug1_07931), are associated with dye degradation. These laccases were heterologously expressed in Pichia pastoris and purified. In vitro experiments demonstrated that the purified laccases efficiently degrade dyes (e.g., RBBR, methyl orange (MO), bromophenol blue (BPB)) in the presence of mediators. When immobilized using copper sulfate (CuSO₄) as the carrier, the laccases retained over 60 % degradation efficiency toward RBBR, MO, and BPB. Gas chromatography-mass spectrometry (GC-MS) analysis of the degradation intermediates of RBBR, MO, and BPB elucidated the potential laccase-mediated dye degradation pathways and products, offering novel insights into the remediation of dye-contaminated environments. This study demonstrates that S. rugosoannulata and its laccases (SrLAC1 and SrLAC9) possess significant potential as effective bioremediation agents for eliminating synthetic dyes from contaminated environments.