Waste Management by Biological Approach Employing Natural Substrates and Microbial Agents for the Remediation of Dyes’ Wastewater

Biological and molecular approaches of the degradation or decolorization potential of the hypersaline Lake Tuz Bacillus megaterium H2 isolate

The presence of synthetic dyes in water bodies and soil is one of the major issues affecting the global ecology, possibly impacting societal well-being adversely due to the colorants' recalcitrance and toxicity. Herein, the study spectrophotometrically monitored the ability of the Bacillus megaterium H2 azoreductase (AzrBmH2) to degrade four synthetic dyes, reactive blue 4, remazol brilliant red, thymol blue, and methyl red, followed by in-silico assessment using GROMACS. We found that the bacterium degraded as much as 60% of all four synthetic dyes at various tested concentrations. The genome analysis revealed five different azoreductase genes, which were then modeled into the AzrBmH21, AzrBmH22/3, and AzrBmH24/5 templates. The AzrBmH2-substrate complexes showed binding energies with all the dyes of between -10.6 to -6.9 kcal/mol and formed 4-6 hydrogen bonds with the predicted catalytic binding residues (His10, Glu 14, Ser 58, Met 99, Val 107, His 183, Asn184 and Gln 191). In contrast, the lowest binding energies were observed for the AzrBmH21-substrates (-10.6 to -7.9). Molecular dynamic simulations revealed that the AzrBmH21-substrate complexes were more stable (RMSD 0.2-0.25 nm, RMSF 0.05 - 0.3 nm) and implied strong bonding with the dyes. The Molecular Mechanics Poisson-Boltzmann Surface Area results also mirrored this outcome, showing the lowest azoreductase-dye binding energy in the order of AzrBmH21-RB4 (-78.18 ± 8.92 kcal/mol), AzrBmH21-RBR (-67.51 ± 7.74 kcal/mol), AzrBmH21-TB (-46.62 ± 5.23 kcal/mol) and AzrBmH21-MR (-40.78 ± 7.87 kcal/mol). In short, the study demonstrated the ability of the B. megaterium H2 to efficiently decolorize the above-said synthetic dyes, conveying the bacterium's promising use for large-scale dye remediation.Communicated by Ramaswamy H. Sarma.

Enhancing Methylene Blue Dye Removal using pyrolyzed Mytella falcata Shells: Characterization, Kinetics, Isotherm, and Regeneration through Photolysis and Peroxidation

The potential of pyrolyzed Mytella falcata shells as an adsorbent for removing methylene blue dye molecules from aqueous solutions was investigated. The study found that the adsorbent produced at 600 °C of pyrolysis temperature, with an adsorbent mass of 0.5 g, particle diameter of 0.297-0.149 mm, and pH 12.0, demonstrated the highest dye molecule removal efficiency of 82.41%. The material's porosity was observed through scanning electron microscopy, which is favorable for adsorption, while Fourier-transform infrared spectroscopy and X-Ray diffraction analysis analyses confirmed the presence of calcium carbonate in the crystalline phases. The pseudo-second order model was found to be the best fit for the data, suggesting that the adsorption mechanism involves two steps: external diffusion and diffusion via the solid pores. The Redlich-Peterson isotherm model better represented the equilibrium data, and the methylene blue adsorption was found to be spontaneous, favorable, and endothermic. The hydrogen peroxide with UV oxidation was found to be the most efficient method of regeneration, with a regeneration percentage of 63% achieved using 600 mmol.L-1 of oxidizing agents. The results suggest that pyrolyzed Mytella falcata shells could serve as an ecologically viable adsorbent alternative, reducing the amount of waste produced in the local environment and at the same time removing pollutants from the water. The material's adsorption capacity remained almost constant in the first adsorption-oxidation cycles, indicating its potential for repeated use.

A critical review for advances on industrialization of immobilized cell Bioreactors: Economic evaluation on cellulose hydrolysis for PHB production

Advances such as cell-on-cell immobilization, multi-stage fixed bed tower (MFBT) bioreactor, promotional effect on fermentation, extremely low temperature fermentation, freeze dried immobilized cells in two-layer fermentation, non-engineered cell factories, and those of recent papers are demonstrated. Studies for possible industrialization of ICB, considering production capacity, low temperatures fermentations, added value products and bulk chemical production are studied. Immobilized cell bioreactors (ICB) using cellulose nano-biotechnology and engineered cells are reported. The development of a novel ICB with recent advances on high added value products and conceptual research areas for industrialization of ICB is proposed. The isolation of engineered flocculant cells leads to a single tank ICB. The concept of cell factories without GMO is a new research area. The conceptual development of multi-stage fixed bed tower membrane (MFBTM) ICB is discussed. Finally, feasible process design and technoeconomic analysis of cellulose hydrolysis using ICB are studied for polyhydroxybutyrate (PHB) production.

High dye removal capacity of Peniophora laxitexta immobilized in a combined support based on polyurethane foam and lignocellulosic substrates

Dye removal from effluents is a major problem for most textile industries. At present, wastewater treatments are currently based on physico-chemical methods which are expensive, energy inefficient and of limited versatility. The aim of this work was to find a low-cost and efficient method for dye removal. To do this, we designed a combined system based on the immobilization of the ligninolytic white-rot fungus Peniophora laxitexta (BAFC 4687) on mixed supports consisting of two polyurethane foam discs and a middle layer of diverse lignocellulosic substrates: soybean hulls, wheat straw or cellulose spent casings. As a corticioid fungus, P. laxitexta was able to completely colonize the supports developing a compact and tight structure that maintained the integrity of the system after several dye removal cycles. The immobilized fungus removed between 30% and 50% of the azoic dye Xylidine and more than 50% of the anthraquinonic dye RBBR in three successive cycles, and near 90% of the triphenylmethane Malachite Green in 10 repeated cycles without any loss of efficiency. Our analysis showed that the removal of the dyes was due to the combined effect of adsorption to the supports and enzymatic decolorization by soluble laccases and enzymes associated with the mycelium. Additionally, we showed that the presence of Malachite Green induced the expression of a new laccase isoform with high decolorization capacity. Based on these results, we propose that this inoculated laminar biocarrier could be effectively used for dye removal in textile wastewater.

Preliminary Studies of Methylene Blue Remotion from Aqueous Solutions by Ocimum basilicum

The continuous expansion in the textile industry results in high loads of coloured wastewaters that heavily pollute the limited freshwater sources. Therefore, a wide array of treatment methods has been used to remediate water/wastewater from dyes. One common practice is the use of plants to degrade, absorb, metabolise, and detoxify different types of pollutants, including dyes. This study employs sweet basil (Ocimum basilicum) as a phytoremediation model herb to remove different concentrations (5–25 mg/L) of methylene blue (MB) dye from synthetic water, taking into account the effects of the MB dye concentration (5–25 mg/L) and contact time (up to 10 days). The results showed that the ability of Ocimum basilicum to absorb MB dye decreased with the increase of the MB dye concentration and increased with the increase of the contact time. The best removal of the MB dye was 93% when the concentration of the MB dye was 25 mg/L and the contact time was 10 days. Additionally, it was noticed that the relative growth rate (RGR) of the herbs was adversely influenced by increasing MB dye concentrations and that the best RGR value was 2.2 g/day when the MB dye concentration was 5 mg/L.

The efficient removal of diclofenac sodium and bromocresol green from aqueous solution by sea urchin-like Ni/Co-BTC bimetallic organic framework: adsorption isotherms, kinetics and mechanism

A novel adsorbent based on nanostructured Ni/Co-BTC bimetallic organic framework (namely Ni/Co-BTC MOF) was successfully prepared by a simple solvothermal method. Adsorption experiments showed that the optimal molar ratio of...

The Use of Sugarcane Bagasse to Remove the Organic Dyes from Wastewater

In the present study, the potential of sugarcane bagasse (SCB) was evaluated by methylene blue (MB) retention. The selected low-cost adsorbent was characterized by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), BET method, and determination of the point of zero charge (pHzpc). Batch kinetic and isothermal studies were performed to examine the effects of contact time, initial dye concentration, adsorbent dose, pH, and temperature. The results show that the kinetic study of MB adsorption on sugarcane bagasse is very fast; the equilibrium is reached after only 20 minutes. The kinetic model of pseudo-second-order and the Langmuir isotherm model perfectly explain the adsorption process of MB with a monolayer adsorption capacity equal to 49.261 mg·g^-1 activation parameters' values such as free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) also determined as -4.35 kJ·mol^-1, -31.062 kJ·mol^-1, and -0.084 J·mol^-1·K^-1, respectively. Besides, the thermodynamic parameters of the methylene blue sugarcane bagasse system indicate that the exothermic adsorption process is spontaneous.