Enhanced removal of dibutyl phthalate in a laccase-mediator system: Optimized process parameters, kinetics, and environmental impact.

The persistence and recalcitrance of endocrine-disrupting chemicals (EDCs) in the environment have raised momentous concerns due to their carcinogenic, teratogenic, genotoxic, and cytotoxic effects on humans, animals, and plants. Unarguably, dibutyl phthalate (DBP) is one of the most ubiquitous EDCs because of its bioavailability in water, soil, and atmosphere. This study aims to investigate the efficiency of Agaricus bisporus laccase in the degradation of dibutyl phthalate (DBP) in laccase-mediator system. Here, enhanced removal efficiency was recorded during DBP degradation in laccase-mediator systems than in reaction medium containing laccase only. About 98.85% of 30 mg L-1 DBP was efficiently removed in a medium containing 1.3 U mL-1, 0.045 mM Syringaldehyde (SYR) at incubation temperature 30 aC and pH 5 within 24 h. This finding was further corroborated by the synergistic interplay of the optimal parameters in the laccase-SYR system done using response surface methodology (Box-Behnken Design). Furthermore, the addition of 1.5 mM of metal ions in the laccase-SYR system further promoted the enhanced removal of DBP in the following order: Cr3+> Pb2+> Ca2+> Al3+>Zn2+ > Cu2+. A significant decrease in DBP degradation was observed at higher concentrations of metal ions above 1.5 mM due to the inhibition of laccase active sites. The coefficient of correlation (R2 = 0.9885) recorded in the Lineweaver bulk plot affirmed that the removal efficiencies are highly dependent on DBP concentration in the laccase-SYR system. The Gas-Chromatography Mass Spectrometry (GC-MS) analyses affirmed that the ortho-cleavage due to hydrolysis of DBP in the reaction system led to the formation of two metabolic degradation products (MBP and PA). The phytotoxicity assessment affirmed the detoxified status of DBP after treatment with significant improvement (90 and 91%) in the growth of Lens culinaris and Sorghum bicolor. This is the first report on DBP degradation in the laccase-SYR reaction system, underscoring the unique, eco-friendly, economical, and promising alternative to known conventional methods.

Degradation and detoxification of reactive yellow dyes by Scedosporium apiospermum: a mycoremedial approach.

Textile industrial effluents have long enunciated the essentiality of ascertaining an efficient wastewater treatment for the removal of azo dyes given their potential disturbances on the ecosystem. Our study investigated the efficiency of the strain SKF2 among 14 other isolates, molecularly identified to be Scedosporium apiospermum, isolated by our research group from the textile effluent sludge in the degradation of two azo dyes, Reactive Yellow 145 and Remazol Yellow RR. Kinetic profiling of the degradation process revealed the decolourisation efficiency to be 94.8 and 86.9% for RY 145 and RYRR, respectively, during the declining growth phase. Laccase and polyphenol oxidase (RY 145-2.37 and RYRR-2.30 U/mL; RY 145-3.26 and RYRR-2.89 U/mL, respectively) were found to influence the biodegradation process in both the dyes than the other examined fungal degradative enzymes. The metabolic pathway predicted with the aid of GC-MS analysis identified the degraded metabolites to be smaller molecular weight non-toxic products. Assessment of toxicity via brine shrimp lethality assay (RY 145-23.3% and RYRR-16.7%, respectively) and seed germination assay (RY 145-96.7% and RYRR-83.3%) further solidified the detoxified status of both the dyes after biodegradation. The experimental data thus substantiated the expediency of S. apiospermum SKF2 in the degradation of textile azo dyes and its further employment in the bioremediation of textile wastewaters for agricultural applications and ecological recycling.

Biodegradation of fluorene by the newly isolated marine-derived fungus, Mucor irregularis strain bpo1 using response surface methodology.

Fluorene, a low molecular weight polycyclic aromatic hydrocarbon (PAH), is of immense environmental interest because of its carcinogenicity, teratogenicity, mutagenicity, toxicity and persistence to microbial degradation. Existentially, there is paucity of information on PAH degradation by fungi isolated from marine environment. Therefore, this study investigated fluorene degradation efficiency of marine derived filamentous fungus, Mucor irregularis strain bpo1 (GenBank Accession Number: MK373020). Response Surface Methodology (RSM) using Box-Behnken Design (BBD) was successfully deployed in the optimization of process parameters (pH-7, temperature-32.5 °C, substrate concentration-100 mg L-1 and dry weight-2 g) resulting in 81.50% fluorene degradation on 5th day. The design and regression model were found to be statistically significant, adequate and appropriate with p < 0.0001, F value= 202.39, and predicted coefficient of determination (R2 =0.9991). Optimization of the vital constituents of the mineral salt medium (MSM) used for the study using RSM-Central Composite Design (CCD) resulted in 79.80% fluorene degradation rate. Enhanced fluorene degradation efficiency (82.50%) was recorded when the optimized process variables were subjected to growth-linked validation experiments. The enzyme activities revealed 87%, 59% and 31% induction of laccase, manganese peroxidase and lignin peroxidase respectively. Four metabolites; 9H-fluoren-9-one, benzene-1,2-dicarboxylic acid, 2-hydroxybenzoic acid and phenol obtained after the experiment were characterized and confirmed with GC-MS analysis. The findings revealed the promising potentials of M. irregularis in PAH degradation and by extension green remediation technology.