Evaluation of several white-rot fungi for the decolorization of a binary mixture of anionic dyes and characterization of the residual biomass as potential organic soil amendment

Microbial approaches for sustainable remediation of dye-contaminated wastewater: a review

The coloured effluents produced from different industries, such as textile, plastics, printing, cosmetics, leather and paper, are extremely toxic and a tremendous threat to the aquatic organisms and human beings. The removal of coloured dye pollutants from the aqueous environment is a great challenge and a pressing task. The growing demand for low-cost and efficient treatment approaches has given rise to alternative and eco-friendly methods, such as biodegradation and microbial remediation. This work summarizes the overview and current research on the remediation of dye pollutants from the aqueous environment by microbial bio-sorbents, such as bacteria, fungi, algae, and yeast. In addition, dye degradation capabilities of microbial enzymes have been highlighted and discussed. Further, the influence of various experimental parameters, such as temperature, pH, and concentrations of nutrients, and dye, has been summarized. The proposed mechanism for dye removal by microorganisms is also discussed. The object of this review is to provide a state-of-the-art of microbial remediation technologies in eliminating dye pollutants from water resources.

Isolation of Fungi from a Textile Industry Effluent and the Screening of Their Potential to Degrade Industrial Dyes

Six fungal strains were isolated from the textile industry effluent in which they naturally occur. Subsequently, the fungal strains were identified and characterized in order to establish their potential decolorizing effect on textile industry effluents. The strains of interest were selected based on their capacity to decolorize azo, indigo, and anthraquinone dyes. Three of the strains were identified as Emmia latemarginata (MAP03, MAP04, and MAP05) and the other three as Mucor circinelloides (MAP01, MAP02, and MAP06), while the efficiency of their decolorization of the dyes was determined on agar plate and in liquid fermentation. All the strains co-metabolized the dyes of interest, generating different levels of dye decolorization. Plate screening for lignin-degrading enzymes showed that the MAP03, MAP04, and MAP05 strains were positive for laccase and the MAP01, MAP02, and MAP06 strains for tyrosinase, while all strains were positive for peroxidase. Based on its decolorization capacity, the Emmia latemarginata (MAP03) strain was selected for the further characterization of its growth kinetics and ligninolytic enzyme production in submerged fermentation under both enzyme induction conditions, involving the addition of Acetyl yellow G (AYG) dye or wheat straw extract, and no-induction condition. The induction conditions promoted a clear inductive effect in all of the ligninolytic enzymes analyzed. The highest level of induced enzyme production was observed with the AYG dye fermentation, corresponding to versatile peroxidase (VP), manganese peroxidase (MnP), and lignin peroxidase (LiP). The present study can be considered the first analysis of the ligninolytic enzyme system of Emmia latemarginata in submerged fermentation under different conditions. Depending on the results of further research, the fungal strains analyzed in the present research may be candidates for further biotechnological research on the decontamination of industrial effluents.

Textile Dye Biodecolorization by Manganese Peroxidase: A Review

Wastewater emissions from textile factories cause serious environmental problems. Manganese peroxidase (MnP) is an oxidoreductase with ligninolytic activity and is a promising biocatalyst for the biodegradation of hazardous environmental contaminants, and especially for dye wastewater decolorization. This article first summarizes the origin, crystal structure, and catalytic cycle of MnP, and then reviews the recent literature on its application to dye wastewater decolorization. In addition, the application of new technologies such as enzyme immobilization and genetic engineering that could improve the stability, durability, adaptability, and operating costs of the enzyme are highlighted. Finally, we discuss and propose future strategies to improve the performance of MnP-assisted dye decolorization in industrial applications.

Trametes versicolor in lignocellulose-based bioeconomy: State of the art, challenges and opportunities

Although Trametes versicolor is one of the most investigated white-rot fungi, the industrial application of this fungus and its metabolites is still far from reaching its full potential. This review aims to highlight the opportunities and challenges for the industrial use of T. versicolor according to the principles of circular bioeconomy. The use of this fungus can contribute significantly to the success of efforts to valorize lignocellulosic waste biomass and industrial lignocellulosic byproducts. Various techniques of T. versicolor cultivation for enzyme production, food and feed production, wastewater treatment, and biofuel production are listed and critically evaluated, highlighting bottlenecks and future perspectives. Applications of T. versicolor crude laccase extracts in wastewater treatment, removal of lignin from lignocellulose, and in various biotransformations are analyzed separately.

Evaluation of a Trametes pubescens laccase concentrated extract on allura red AC decolorization without the addition of synthetic mediators

Synthetic dye bioremediation is a topic of great importance since these pollutants possess toxic effects, and huge quantities of them are being discharged into water bodies. Ligninolytic enzyme treatment stands out for being a cost-effective methodology, capable of obtaining high decolorization levels. In this work, a laccase enzyme treatment was evaluated to effectively perform a cycle of dye bioremediation. Furthermore, a dye decolorization improvement was also assessed through laccase immobilization. Particularly, a Trametes pubescens enzyme extract was concentrated, immobilized onto calcium alginate beads, and characterized to assess its dye decolorization potential. Ammonium sulfate precipitation and vacuum evaporation were evaluated to concentrate the crude extract and to decolorize allura red AC. Both treatments reached a high enzyme yield recovery (>90%), but only the vacuum-evaporated extract achieved a high allura red AC decolorization level after 16 h of contact time. This suggested that essential compounds for allura red AC decolorization were present in the crude extract, implying that neither a complete laccase purification process nor an addition of synthetic mediators are necessary. Under optimized immobilization conditions, 94.6% immobilization efficiency and 49.8% activity recovery were obtained with 0:1 alginate:enzyme (v/v), 100 mM CaCl₂, and 5.0% w/v sodium alginate. Furthermore, by immobilizing the laccase concentrated extract, both the pH and temperature stabilities were improved. The decolorization of allura red AC by free and immobilized laccase was 68.4% and 4.6%, respectively, showing that although the enzyme stability was improved, dye decolorization was negatively affected. Thus, an efficient allura red AC decolorization was obtained with concentrated-free laccase by a feasible and low-cost methodology.

Synthetic dyes biodegradation by fungal ligninolytic enzymes: Process optimization, metabolites evaluation and toxicity assessment

This work aimed to provide information that contributes to establishing environmental-friendly methods for synthetic dyes' degradation. The potential decolorization capacity of the crude enzymatic extract produced by Phanerochaete chrysosporium CDBB 686 using corncob as a substrate was evaluated on seven different dyes. Critical variables affecting the in-vitro decolorization process were further evaluated and results were compared with an in-vivo decolorization system. Decolorization with enzymatic extracts presented advantages over the in-vivo system (higher or similar decolorization within a shorter period). Under improved in-vitro process conditions, the dyes with higher decolorization were: Congo red (41.84 %), Poly R-478 (56.86 %), Methyl green (69.79 %). Attempts were made to confirm the transformation of the dyes after the in-vitro process as well as to establish a molecular basis for interpreting changes in toxicity along with the degradation process. In-vitro degradation products of Methyl green presented a toxicity reduction compared with the original dye; however, increased toxicity was found for Congo red degradation products when compared with the original dyes. Thus, for future applications, it is crucial to evaluate the mechanisms of biodegradation of each target synthetic dye as well as the toxicity of the products obtained after enzymatic oxidation.