Exploring fungal-mediated solutions and its molecular mechanistic insights for textile dye decolorization.

Decolorization of textile dyes and study of their intermediate compounds is necessary to comprehend the mechanism of dye degradation. In the present study, different fungal mediated solutions were explored to provide an alternative to treat the reactive dyes. Growing biomass of Pleurotus sajor caju showed 83% decolorization (249.99 mg L-1 removal) of Reactive Blue 13 (RB 13) and 63% decolorization (188.83 mg L-1) of Reactive Black 5 (RB 5) at 300 mg L-1 initial concentration on 8 d. Higher laccase activity was positively correlated with increase in decolorization. However, increasing dye concentration has inhibitory effect on fungal biomass due to increase in toxicity. In laccase mediated decolorization, laccase produced from P. sajor caju using carbon rich waste material as substrate showed 89% decolorization (276.36 mg L-1 removal) of RB 13 and 33% decolorization (105.37 mg L-1 removal) of RB 5 at 300 mg L-1 initial dye concentration in 100 min at 30 °C and pH 3.0'. Comparing the two methods, laccase-mediated decolorization shows better decolorization in less time and does not produce sludge. Further, the present work also attempted to study the dye degradation pathway for Reactive blue 13 via laccase mediated process. Fourier-transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC), and gas chromatography-mass spectrometry (GC-MS) were utilized to identify the degraded products. The GC-MS analysis showed the formation of naphthalene, naphthalene 2-ol, benzene,1-2, dicarboxylic acid, 4, amino, 6,chloro, 1-3-5, triazin-2-ol as the final degraded products after enzymatic degradation of RB 13. These findings provide in-depth study of laccase-mediated textile dye degradation mechanism.

Unveiling the azo-reductase mechanism in Pseudomonas putida for efficient decolorization of textile Reactive dyes: an in-silico study.

The textile industry utilizing affordable azo dyes is a high threat to aquatic life and causes environmental problems due to their toxicity. Biodegradation of azo dyes employing microbes and enzymes has proved to be an efficient method for treating industrial effluent. This study used the novel microbial consortium to decolorize reactive azo dyes (Reactive Red 120; Reactive Black 5 and Reactive Blue 13), and its azo-reductase activity was evaluated. The metagenomic analysis of the consortium identified azo-reductase-producing bacterial species. The molecular docking revealed that PpAzoR from Pseudomonas putida had the highest binding affinities for all the three dyes such as Reactive Black 5 (-9.3 kcal/mol), Reactive Blue 13 (-9.8 kcal/mol) and Reactive Red 120 (-10.7 kcal/mol). The structural rigidity and stability of the docked complex were confirmed through MD simulations evaluated across multiple descriptors from the simulation trajectories. Further, MMPBSA analysis validated the results that binding of the ligands, i.e. dye molecules Reactive Black (RB5), Reactive Blue (RB13) and Reactive Red (RR120) binding with the Azoreductase (PpAzoR) to the screened Azo-dyes was spontaneous. Based on molecular dynamics simulations for 100 ns, RR 120 showed the highest binding affinity (-411.336 ± 46.799 KJ/mol), followed by RB5 (-288.012 ± 33.371 KJ/mol). The dyes (RR120 and RB5) exhibited stable interactions with the target azoreductase (PpAzoR). The present study provides insights that PpAzoR shows the highest decolorization potency, which could be interpreted as a potential dye-degrading protein based on dye-degrading assay findings.Communicated by Ramaswamy H. Sarma.

>90% decolourization observed for all reactive dyes at 72 hAzo reductase-producing bacterial species were identified using metagenomicsPseudomonas putida (PpAzoR) showed maximum binding affinity with all three dyesPositive correlation was established between dye decolourization and in-silico results.

Life cycle assessment of sequential microbial-based anaerobic-aerobic reactor technology developed onsite for treating textile effluent.

Although biological treatment of textile effluent is a preferred option for industries avoiding toxic chemical sludge production and disposal, requirement of several extra pre-treatment units like neutralization, cooling systems or additives, results in higher operational cost. In the present study, a pilot scale sequential microbial-based anaerobic-aerobic reactor technology (SMAART) was developed and operated for the treatment of real textile effluent in the industrial premises in continuous mode for 180 d. The results showed an average ∼95% decolourization along with ∼92% reduction in the chemical oxygen demand establishing the resilience against fluctuations in the inlet parameters and climate conditions. Moreover, the pH of treated effluent was also reduced from alkaline range (∼11.05) to neutral range (∼7.76) along with turbidity reduction from ∼44.16 NTU to ∼0.14 NTU. A comparative life cycle assessment (LCA) of SMAART with the conventional activated sludge process (ASP) showed that ASP caused 41.5% more negative impacts on environment than SMAART. Besides, ASP had 46.15% more negative impact on human health, followed by 42.85% more negative impact on ecosystem quality as compared to SMAART. This was attributed to less electricity consumption, absence of pre-treatment units (cooling and neutralization) and less volume of sludge generation (∼50%) while using SMAART. Hence, integration of SMAART within the industrial effluent treatment plant is recommended to achieve a minimum waste discharge system in pursuit of sustainability.

Hybrid electrocoagulation and laccase mediated treatment for efficient decolorization of effluent generated from textile industries.

Enzymatic (laccase mediated) decolorization of dyes remains inefficient for recalcitrant dyes, which can be better handled by electrocoagulation (EC). However, EC is energy intensive and produce large amount of sludge. In light of the same, present study offers a promising solution for the treatment of textile effluent meeting surface discharge norms, using hybridization of enzymatic and electrocoagulation treatment. The findings revealed best color removal (90%) of undiluted (raw) textile effluent (4592 hazen) is achievable by employing EC using zinc-coated iron electrode at current density 25 mA cm-2 followed by partially purified laccase (LT) treatment, and activated carbon (AC) polishing at ambient conditions. Overall, the decolorization performance of Hybrid EC-LT integrated AC approach was 1.95 times better than only laccase treatment. Also, the sludge generation from Hybrid EC-LT integrated AC (0.7 g L-1) was 3.3 times lesser than EC alone (2.1 g L-1). Therefore, the present study recommends Hybrid EC-LT integrated AC could be potential approach to treat complex textile effluent sustainably with lower energy input and waste sludge generation.

Mechanistic insights on enzyme mediated-metabolite cascade during decolourization of Reactive Blue 13 using novel microbial consortium.

Understanding the role of oxido-reductase enzymes followed by deciphering the functional genes and their corresponding proteins are crucial for the speculation of molecular mechanism for azo dye degradation. In the present study, decolourization efficiency of developed microbial consortium was tested using 100 mgL-1 reactive blue 13 (RB13) and the results showed ∼92.67% decolourization of RB13 at 48 h of incubation. The fourier-transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) analysis were performed to identify the metabolites formed during RB13 degradation, followed by hypothesizing the metabolic pathway. The GC-MS analysis showed formation of 1,4-dihydronaphthalen-1-ol and 1,3,5-triazin-2-amine as the final degraded compounds after enzymatic breakdown of RB13 dye. The activity of different oxido-reductase enzymes was determined, and the results showed that NADH DCIP reductase and azo reductase had higher activity than other enzymes. It clearly indicated the degradation was initiated with the enzymatic cleavage of azo bond of RB13. Further, the functional genes were annotated against the database of clusters of orthologous groups (COGs) and kyoto encyclopedia of genes and genomes (KEGG). It provided valuable information about the role of crucial functional genes and their corresponding proteins correlated with dominant bacterial species in degradation of RB13. Hence, the present research is the first systematic study that correlated the formation of degradation compounds with the functional genes/enzymes and their corresponding bacterial species responsible for RB13 degradation.

A biphasic photobioreactor system for consecutive extraction of lipids and carotenoids from pre-hydrolysed microalgae and evaluation of its biodiesel potential.

A green extraction method is developed using partially hydrolysed microalgal cells grown in biocompatible solvent for simultaneous cultivation and extraction of bioproducts from a highly efficient permeabilized microalgal cell with enhanced biomass and lipid content for potential use in biodiesel production. Incomplete digestion of cell wall was achieved by regulating the incubation time of the enzymatic pretreatment of the microalgal cells. 15.77% increase in lipid content was seen when untreated cells were cultured with biocompatible solvent, while cultivation of these enzymatically pretreated cells with biocompatible solvent, the lipid content increased by 53.33% and 22% higher carotenoid content was observed as compared to conventional extraction. The total fatty acids obtained after 1st and 2nd extractions in untreated samples were 67.82%, while those in enzymatically partially digested samples were 91.94%. The untreated and partially enzymatically predigested strain showed suitable properties for quality biodiesel production as per international recommendations. The cost benefit analysis of the overall process showed the use of biocompatible solvent coupled to enzymatically predigested biomass was a favorable option as compared to conventional extraction.

Melioration of Paddy Straw to produce cellulase-free xylanase and bioactives under Solid State Fermentation and deciphering its impact by Life Cycle Assessment.

Aiming towards zero waste management of Paddy straw (PS), the study offers a novel route for production of cellulase-free xylanase, using consortia of Trichoderma spp. under Solid State Fermentation (SSF) of PS valorized using nitrogen rich de-oiled neem cake (NC). Life Cycle Assessment (LCA) for enzyme production, performed using SimaPro software, depicted adverse impacts due to electricity consumption (92.84%) and use of ammonium sulphate salt (6.17%). Nonetheless, employing renewable energy and reducing salt consumption could help minimize these impacts. OHR-LCMS study of the partially purified enzyme revealed the presence of ß-xylanase and α-L-Arabinofuranosidase. Enzymatic saccharification of various substrates enhanced the release of reducing sugars (mg/g) from corn cob (137.54 ± 0.96), pine needle (41.43 ± 1), sugarcane bagasse (105.17 ± 0.7), and PS (76.66 ± 1.29), demonstrating its applicability in the biofuel domain. LC-MS, ICMPS, and EDX profiling of the residual spent unravelled the manifestation of bioactives, minerals, and silica, playing an essential role as biopesticide and biofertilizer.

Decolourization of textile effluent using native microbial consortium enriched from textile industry effluent.

A robust and efficient treatment process is required to address the problem of residual colour and avoid expensive post-treatment steps while dealing with textile effluents. In the present work, a novel microbial consortium enriched from textile effluent was used to optimize the process of decolourization under extreme conditions with minimum inputs. With PreTreatment Range (PTR) effluent as a carbon source and only 0.5 g/L yeast extract as external input, the process enabled 70-73% colour reduction (from 1910-1930 to 516-555 hazen) in dyeing unit wastewater. Unhindered performance at higher temperatures (30 °C-50 °C) and wide pH range (7-12) makes this process highly suitable for the treatment of warm and extremely alkaline textile effluents. No significant difference was observed in the decolourization efficiency for effluents from different batches (Colour: 1647-4307 hazen; pH-11.5-12.0) despite wide variation in nature and concentration of dyes employed. Long term (60 days) continuous mode performance monitoring at hydraulic retention time of 48 h in lab-scale bioreactor showed consistent colour (from 1734-1980 to 545-723 hazen) and chemical oxygen demand (1720-2170 to 669-844 mg/L) removal and consistently neutral pH of the treated water. Present study thus makes a significant contribution by uncovering the ability of native microbial consortium to reliably treat dye laden textile wastewater without any dilution or pre-treatment and with minimum external inputs. The results ensure easy applicability of this indigenously developed process at the industrial scale.

Improved methane yield from wastewater grown algal biomass.

Methane production from the algal biomass cultivated in a laboratory scale continuous photobioreactor (PBR) using sewage was evaluated in the present work. During the preliminary experiments, algal biomass reached up to 1.69 ± 0.35 g L-1 in 12 days' growth period. Besides, 65 to 100% removal in concentrations of total dissolved phosphorus (TDP), nitrate nitrogen (NO3-N), total ammoniacal nitrogen (TAN) and soluble chemical oxygen demand (sCOD) was also recorded. The sCOD removal in the reactor was 100%, whereas removal of TDP, NO3-N and TAN were up to 75, 40 and 92%, respectively. Upon anaerobic digestion, the fresh algal biomass showed methane yield of 180 mL g-1 VSfed. Further, algal biomass was stored under natural conditions in open containers (aerobic conditions) in darkness at room temperature (27-30 °C) for 72 h. Interestingly, >48% COD solubilization from algal biomass was observed during storage. Pretreatment through natural storage was further confirmed with qualitative observations including scanning electron and fluorescence microscopic analysis. Moreover, higher methane yield (284.38 mL g-1 VSfed) was observed from the samples stored for 60 h. Thus, natural storage for a designated period may be recommended as a prerequisite stage in the process of methane production from wastewater-grown algal biomass.