Enhanced decolorization and biodegradation of acid red 88 dye by newly isolated fungus, Achaetomium strumarium

Acid red 88 dye degradation efficiency of newly isolated filamentous fungus, Achaetomium strumarium were investigated. Molecular studies of 23S rRNA sequence data confirmed the phylogenetic clade relationship of the isolate with members of the same genus, Achaetomium. Achaetomium strumarium decolorized (99%) of 10 mg L−1 of acid red 88 dye at pH (4), biomass dose (2000 mg) and temperature (40 °C) within 96 h. Further studies revealed that decolorization was enhanced with the addition of calcium salts in the reaction medium resulting in maximum amount of dye adsorbed (35.55 mg g−1). The experimental data showed the best goodness of fit when subjected to Temkin isotherm model (R2 = 0.985) in comparison with Freundlich and Langmuir isotherm models (R2 = 0.883 and 0.688) respectively. The adsorption mechanism followed pseudo-second order kinetic model (R2 = 0.997) indicating the influence of the AR88 dye molecules and fungal biomass. Enzymes analysis revealed significant inductions and role played by NADH-DCIP reductase and laccase in the asymmetric cleavage, dehydroxylation, and desulfonation of AR-88 dye. Metabolites of the acid red 88 dye after degradation were analyzed using UV-vis spectroscopy, FTIR, HPLC and GCMS. The GCMS analysis revealed the production of three intermediates; naphthalen-2-ol, sodium naphthalene-1-sulfonate and 1,4-dihydronaphthalene. Possible metabolic fate pathway for the degradation of AR88 dye by A. strumarium was proposed. The results obtained from toxicity studies revealed the AR-88 dye detoxification efficiency of Achaetomium strumarium and hence, in its myco-transformation.