Biodegradation of Synthetic Effluent Containing CI Direct Red 28 (Congo Red) by Lentinus sp. Laccase Leads to Low Ecotoxicity

Background: Azo dyes are widely used recalcitrant chemicals and may promote environmental hazards. Amongst the known azo dyes is CI Direct Red 28 (C32H22N6Na2O6S2) aka Congo Red (CR), which is a known mutagen and carcinogen. In this regard, this work aimed at the biodegradation of a CR-containing synthetic effluent, and the evaluation of the ecotoxicity of post-treatment residues. Methods: Lentinus sp. Laccase (Lac)-mediated bioremediation of CR was optimized upon added concentrations of sucrose and CuSO4, moreover a standard ecotoxicity assay was performed. Results: Results showed that the addition of 5% sucrose and 2 mM CuSO4 increased CR degradation, with Lac activity at 48 h of 30.2 U mL-1, and at 72 h of 31.9 U mL-1. Moreover, the ecotoxicity assay showcased that CR degradation by Lentinus sp. Lac seemingly generated low ecotoxic byproducts. Conclusion: Given that CR bioremediation byproducts were known to exhibit high toxicity, our results shed light on the use of Lentinus sp. catalytic arsenal to promote proper remediation of azo dyepolluted effluents.