Enzymatic and Non-Enzymatic decolorization of synthetic dyes using spent mushroom substrate

Conventional wastewater treatment technologies exhibit limited cost-effectiveness for dye removal. This study investigated the decolorization efficacy and adsorption behavior of spent mushroom substrate (SMS) and its aqueous extract (SMS-T) toward ten synthetic dyes, both before and after thermal treatment. SMS achieved total decolorization rates of 72.65-97.84% across the tested dyes. Adsorption by the SMS matrix accounted for only 0.68-36.46% of decolorization for Bromophenol Blue, Malachite Green, Methylene Blue, Rose Bengal, and Remazol Brilliant Blue R, substantially lower than the differential removal (8.25-71.63%) between SMS and SMS-T. This indicates the existence of a non-adsorptive decolorization mechanism mediated by water-insoluble SMS components. Comparative analysis of SMS-T before and after heat treatment revealed that thermally processed SMS-T maintained > 30% decolorization efficiency for Methylene Blue, Brilliant Blue G, and Crystal Violet. Notably, decolorization rates for Rose Bengal and Remazol Brilliant Blue R showed no significant difference post-treatment, demonstrating the presence of heat-stable non-enzymatic decolorization mechanisms in SMS-T. Isothermal adsorption studies indicated that the Langmuir model optimally described SMS adsorption for Congo Red, Aniline Blue, Malachite Green, and Remazol Brilliant Blue R. In contrast, the Freundlich model better fitted the other six dyes. Concurrently, SMS achieved effective decolorization and partial toxicity reduction when treating simulated textile effluent (STE). This work proposes two complementary mechanisms governing SMS-mediated decolorization: non-adsorptive decolorization by water-insoluble SMS fractions and heat-resilient non-enzymatic pathways in SMS-T. These findings establish SMS as a multifunctional bioremediation agent, providing an integrated physicochemical-biological strategy for treating complex dye-laden wastewater.