Phenol-mediated decolorization and removal of disperse dyes by bitter gourd (Momordica charantia) peroxidase

Synthesis of nickel nanoparticles using Citrullus colocynthis stem extract for remediation of Reactive Yellow 160 dye

In current years, pollution caused by synthetic dyes has become one of the most serious environmental issues. By rapidly developing industrial units, effluents having synthetic dyes are directly or indirectly being discharged into the environment. Bio-sorption is cost-effective way for the eradication of toxic dyes present in textile effluent. The present study involves the synthesis of nickel nanoparticles using Citrullus colocynthis stem extract. The characterization of synthesized nickel nanoparticles (Ni-NPs) was done by SEM. The synthesized Ni-NPs were used to degrade the Reactive Yellow 160 dye following the optimization of different experimental parameters. The maximum decolorization (91.4%) was obtained at 0.02% dye conc., 9 mg/L conc. of Ni-NPs, pH 7 at 40 °C. TOC and COD were used to assess the efficiency of this experiment. Percent reduction in COD and TOC was found to be 84.35% and 83.24% respectively. The degradation pathway of dye under study confirmed the formation of non-toxic end-products.

Oxidative Catalysis by TAMLs: Obtaining Rate Constants for Non-Absorbing Targets by UV-Vis Spectroscopy

Understanding the catalysis of oxidative reactions by TAML activators of peroxides, i. e. iron(III) complexes of tetraamide macrocyclic ligands, advocated a spectrophotometric procedure for quantifying the catalytic activity of TAMLs for colorless targets (k_II ', M^-1  s^-1 ), which is incomparably more advantageous in terms of time, cost, energy, and ecology than NMR, HPLC, UPLC, GC-MS and other similar techniques. Dyes Orange II or Safranin O (S) are catalytically bleached by non-excessive amount of H₂ O₂ in the presence of colorless substrates (S₁ ) according to the rate law: -d[S]/dt=k_I k_II [H₂ O₂ ][S][TAML]/(k_I [H₂ O₂ ]+k_II [S]+k_II '[S₁ ]). The bleaching rate is thus a descending hyperbolic function of S₁  : v=ab/(b+[S₁ ]). Values of k_II ' found from a and b for phenol and propranolol with commonly used TAML [Fe^III {o,o'-C₆ H₄ (NCONMe₂ CO)₂ CMe₂ }₂ (OH₂ )]⁺ are consistent with those for S₁ (phenol, propranolol) obtained directly by UPLC. The study sends vital messages to enzymologists and environmentalists.

A combination of absorption and enzymatic biodegradation: phenol elimination from aqueous and organic phase

Peroxidase from Brassica rapa was immobilized as cross-linked enzyme aggregates (CLEAs) and used to treat air containing phenol as a model molecule of volatile organic compounds (VOCs). Prior to an enzymatic treatment, phenol was absorbed into an aqueous or organic phase (silicone oil) to reach concentrations ranging from 20 to 160 mg/L. The process was carried out by introducing a desired weighing of BRP-CLEAs into preparations and reaction was started by injecting H₂O₂ solution to the medium. Optimization of the reaction conditions in the organic solvent revealed an optimal contact time of 60 min, 60 mg/L of phenol concentration and 3 mM H₂O₂, leading to a maximum removal yield of 70% for 3.4 UI/mL of BRP-CLEAs. These results were compared to those obtained in an aqueous medium that showed 90% of degradation yield after 40 min in the following conditions, 90 mg/L of initial phenol amount, 2 mM of H₂O₂ and 2.5 UI/mL of BRP-CLEAs. Parameters of the Michaelis-Menten model, Km and Vmax, were also determined for the reaction in both phases. Phenol removal by BRP-CLEAs in silicone oil succeeded with 70% of conversion yield. It is promising regarding the transposition of such enzymatic process to hydrophobic VOCs.

Concurrent uptake and metabolism of dyestuffs through bio-assisted phytoremediation: a symbiotic approach

Manipulation of bio-technological processes in treatment of dyestuffs has attracted considerable attention, because a large proportion of these synthetic dyes enter into natural environment during synthesis and dyeing operations that contaminates different ecosystems. Moreover, these dyestuffs are toxic and difficult to degrade because of their synthetic origin, durability, and complex aromatic molecular structures. Hence, bio-assisted phytoremediation has recently emerged as an innovative cleanup approach in which microorganisms and plants work together to transform xenobiotic dyestuffs into nontoxic or less harmful products. This manuscript will focus on competence and potential of plant-microbe synergistic systems for treatment of dyestuffs, their mixtures and real textile effluents, and effects of symbiotic relationship on plant performances during remediation process and will highlight their metabolic activities during bio-assisted phytodegradation and detoxification.

Study of bio-degradation and bio-decolourization of azo dye by Enterobacter sp. SXCR

The objective of this study was to evaluate the decolourization potential of textile dyes by a relatively newly identified bacteria species, Enterobacter sp. SXCR which was isolated from the petroleum polluted soil samples. The bacterial strain was identified by 16S rRNA gene sequence analysis. The effects of operational conditions like initial dye concentration, pH, and temperature were optimized to develop an economically feasible decolourization process. The isolate was able to decolourize sulphonated azo dye (Congo red) over a wide range (0.1-1 gl(-1)), pH 5-9, and temperature 22-40 degrees C in static condition. Anaerobic condition with minimal salt medium supplemented with 2 gl(-1) glucose, pH 7 and 34 degrees C were considered to be the optimum decolourizing condition. The bacterial isolate SXCR showed a strong ability to decolourize dye (0.2 gl(-1)) within 93 h. The biodegradation was monitored by UV-vis, fourier transform infra-red spectroscopy (FTIR) spectroscopy and high performance liquid chromatography (HPLC). Furthermore, the involvement of azoreductase in the decolourization process was identified in this strain. Cells of Enterobacter cloacae were immobilized by entrapment in calcium-alginate beads. Immobilized bacterial cells were able to reduced azo bonds enzymatically and used as a biocatalyst for decolourization of azo dye Congo red. Michaelis-Menten kinetics was used to describe the correlation between the decolourization rate and the dye concentration.

Continuous tank reactors in series: an improved alternative in the removal of phenolic compounds with immobilized peroxidase

Immobilized derivatives of soybean peroxidase, covalently bound to a glass support, were used in a continuous stirred tank reactor in series, in order to study the removal of two phenolic compounds: phenol and 4-chlorophenol. The use of two reactors in series, rather than one continuous tank, improved the removal efficiencies of phenol and 4-chlorophenol. The distribution of different amounts of enzyme between the two tanks showed that the relative distributions influenced the removal efficiency reached and the degree of the enzyme deactivation. The highest removal percentages were reached at the outlet of the second tank for a distribution of 50% of the enzyme in each tank. However, with a distribution of 75% in the first tank and 25% in the second, the elimination percentage in the second tank was slightly lower than in the previous case, and the effects of deactivation of the enzyme in the first tank were less pronounced. In all the distributions assayed it was observed that the first tank acts as a filter for the second one, which receives a feed with a smaller load of phenolic compounds, thus diminishing enzyme deactivation in the second tank.