Progress and perspectives on microbial dye remediation: enzymatic pathways, microbial diversity, and hybrid microbial-based technologies

Abstract

Synthetic dyes are extensively used in the textile industry and related industries. These structurally stable dyes persist in aquatic systems and cause severe ecotoxicological and human health risks. Widely applied conventional physicochemical treatments are constrained by high costs, sludge production, and incomplete mineralization. This review emphasizes the microbial diversity (i.e., fungi, bacteria, yeast, algae, and consortia) and enzymatic (azoreductase, laccases, peroxidase, etc.) machinery responsible for the reductive and oxidative transformation of recalcitrant dyes. Accessible plate and spectrophotometric assays are some enzymatic identification methods that have been discussed alongside some scalable production strategies (i.e., immobilization, fed-batch, and continuous systems). Upstream resource demand has been highlighted in sustainability assessments, but reduced sludge, less chemical input, and energy recovery revealed downstream gains. Furthermore, compared with conventional adsorbents, hybrid microbial technologies have demonstrated a broader substrate range and technoeconomic competitiveness. While, under optimized laboratory conditions, 80–100% decolorization could be achieved, scaling up to real wastewater matrices, maintaining the stability of microbial consortia, and ensuring the biosafety of nanomaterials are some persistent challenge. Future studies should include long-term pilot trials, omics-assisted microbial design, multispecies microcosm studies, and biomass valorization.