Eco-friendly detoxification of hazardous Congo red dye using novel fungal strain Trametes flavida WTFP2: Deduced enzymatic biomineralization process through combinatorial in-silico and in-vitro studies

Growing textile industry is a major global concern, owing to the presence of recalcitrant hazardous pollutants, like synthetic dyes in discharged effluents. To explore new bioresources for mycoremediation, a high laccase-producing novel white-rot fungus (WRF), Trametes flavida WTFP2, was employed. T. flavida is an underexplored member of Polyporales. Using bioinformatic tools, 8 different cis-acting RNA elements were identified in the 5.8 S ITS gene sequence, where CRISPR (CRISPR-DR15), sRNA (RUF1), and snoRNA (ceN111) are uniquely present. Molecular docking was adopted to predict the catalytic interaction of chosen toxic diazo colorant, Congo red (CR), with four dye-degrading enzymes (laccase, lignin peroxidase, azoreductase, and aryl alcohol oxidase). With 376.41 × 10³ U/L laccase production, novel WRF exhibited dye-decolorization potential. WTFP2 effectively removed 99.48 ± 0.04% CR (100 mg/L) and demonstrated remarkable recyclability and persistence in consecutive remediation trials. Mycelial dye adsorption was not only substantial driver of colorant elimination; decolorization using active T. flavida was regulated by enzymatic catalysis, as outlined by in-vitro growth, induction of extracellular enzymes, and FESEM. Fifteen metabolites were identified using HRLCMS-QTOF, and novel CR degradation pathway was proposed. Furthermore, microbial and phyto-toxicity tests of metabolites suggested complete detoxification of toxic dye, making the process clean, green, and economically sustainable.

Elucidation of fungal dye-decolourizing peroxidase (DyP) and ligninolytic enzyme activities in decolourization and mineralization of azo dyes

AIM

The aim of the study is to investigate the efficiency of Geotrichum candidum in the decolourization and mineralization of synthetic azo dyes.

METHODS AND RESULTS

It includes screening of enzymes from G. candidum and its optimization, followed by decolourization and mineralization studies. Decolourization was observed to be maximum in methyl orange (94·6%) followed by Congo red (85%), trypan blue (70·4%) and Eriochrome Black T (55·6%) in 48 h, suggesting the plausible degradation of the azo dyes by G. candidum. The enzyme activity study showed that DyP-type peroxidase has highest activity of 900 mU ml^-1 compared to that of laccase (405 mU ml^-1 ) and lignin peroxidase (LiP) (324 mU ml^-1 ) at optimized pH (6) and temperature (35°C). Moreover, the rate of decolourization was found to be directly proportional to the production of laccase and LiP, unlike DyP-type peroxidase. Furthermore, mineralization study demonstrated reduction in aromatic amines, showing 20% mineralization of methyl orange.

CONCLUSION

Geotrichum candidum with its enzyme system is able to efficiently decolourize and mineralize the experimental azo dyes.

SIGNIFICANCE AND IMPACT OF THE STUDY

The efficient decolourization and mineralization of azo dyes makes G. candidum a promising alternative in the treatment of textile effluent contaminated with azo dyes.

Lignolytic mushroom Lenzites elegans WDP2: Laccase production, characterization, and bioremediation of synthetic dyes

A mycoremedial study was undertaken for decolourization of synthetic dyes using wood rot fungal culture Lenzites elegans WDP2. The culture was isolated from decaying wood as fruiting body, and identified on the basis of 5.8S ITS rRNA gene sequence analysis. Qualitative plate screening of culture showed extracellular laccase and lignin peroxidase production, while only laccase enzyme was produced in higher amount (156.793 Uml^-1) in minimal salt broth medium containing glucose and veratryl alcohol. Laccase activity was increased up to 189.25 Uml^-1 after optimization of laccase production by optimization of one variable at a time approach. Molecular characterization of laccase enzyme was done using SDS PAGE and Native PAGE based isozyme analyses. The culture was able to decolorize three synthetic dying compounds (congo red, Malachite green and brilliant green) in broth media, while showed very less decolourization in plate assay. The fungal culture varied in their dye decolourizing potential in broth culture, showing 92.77%, 21.27% and 98.8% maximum decolourization of brilliant green, malachite green and congo red respectively. The congo red dye was completely bio-absorbed by fungal culture within one month. The fungal decolourized broth also revealed the extracellular laccase activity; varied from 10 Uml^-1 to 68.5 Uml^-1 in all the three cases, supports the involvement of laccase enzyme in decolorization. Phase contrast microscopy clearly revealed bio-sorption of the dyes by fungal culture into the mycelium/spores in the photomicrographs.