Modelling of Reactive Black 5 decolourization in the presence of heavy metals by the newly isolated Pseudomonas aeruginosa strain Gb30

Functional genomic analysis of an efficient indole degrading bacteria strain Alcaligenes faecalis IITR89 and its biodegradation characteristics

Indole is a nitrogenous heterocyclic aromatic pollutant often detected in various environments. An efficient indole degrading bacterium strain IITR89 was isolated from River Cauvery, India, and identified as Alcaligenes faecalis subsp. phenolicus. The bacterium was found to degrade ~ 95% of 2.5 mM (293.75 mg/L) of indole within 18 h utilizing it as a sole carbon and energy source. Based on metabolite identification, the metabolic route of indole degradation is indole → (indoxyl) → isatin → (anthranilate) → salicylic acid → (catechol) → (Acetyl-CoA) → and further entering into TCA cycle. Genome sequencing of IITR89 revealed the presence of gene cluster dmpKLMNOP, encoding multicomponent phenol hydroxylase; andAbcd gene cluster, encoding anthranilate 1,2-dioxygenase ferredoxin subunit (andAb), anthranilate 1,2-dioxygenase large subunit (andAc), and anthranilate 1,2-dioxygenase small subunit (andAd); nahG, salicylate hydroxylase; catA, catechol 1,2-dioxygenase; catB, cis, cis-muconate cycloisomerase; and catC, muconolactone D-isomerase which play an active role in indole degradation. The findings strongly support the degradation potential of strain IITR89 and its possible application for indole biodegradation.

Optimization, kinetics, and thermodynamics aspects in the biodegradation of reactive black 5 (RB5) dye from textile wastewater using isolated bacterial strain, Bacillus albus DD1

This study is aimed to model and optimize the decolorization of reactive black 5 (RB5) dye using Bacillus albus DD1. The response surface methodology (RSM) along with rotatable central composite design (rCCD) is used to optimize the response, % decolorization with four input variables: (i) pH (5-9), initial dye concentration (50-500 ppm), the composition of yeast extract as nitrogen source (0.2-1%) and amount of bacterial inoculum (5-25% v/v). The % decolorization is predicted to be ≈ 98% at the optimized condition (pH = 7.6, dye concentration = 200 ppm, bacterial inoculum = 20 v/v% and yeast extract = 0.4%). Furthermore, the kinetics and thermodynamics of RB5 degradation are also determined. The kinetic order of biodegradation of RB5 is found to follow first-order kinetics with a kinetic rate constant = 0.0384. The activation energy, E_a and frequency factor, A values are calculated as 34.46 kJ/mol and 24,343 (1/Day). A thermodynamic study is also carried out at different temperatures (298 K, 308 K, 310 K, 313 K, and 318 K) using optimized conditions. The values of the ΔH and ΔS are found to be +30.79 kJ/mol, and -0.1 kJ/mol/K, respectively using the Eyring-Polanyi equation. The values of ΔG are also calculated at all temperatures.

Optimization of reactive black 5 decolorization by the newly isolated Saccharomyces cerevisiae X19G2 using response-surface methodology

In the current investigation, the capacity of different yeast strains to decolorize reactive black 5 (RB-5) was assessed. A comparative study between the different strains demonstrated that Saccharomyces cerevisiae X19G2 exhibited the highest decolorization rate (69.20 ± 1.16%) after 48 h of incubation. This strain was selected to optimize the medium components' concentrations for maximum RB-5 decolorization. Response-surface methodology (RSM) was tested for the most significant parameters (glucose, yeast extract and RB-5 dye concentrations) that were previously determined by Plackett-Burman design. A dye decolorization rate of 99.59 ± 0.24% was achieved within 48 h using a maximum RB-5 concentration (0.15 g/L) with glucose and yeast extract concentrations equalling to 10.5 g/L and 1 g/L, respectively. Experimental data results proved to fit well with the pseudo-second order kinetics model. The phytotoxicity assessment was carried out using Raphanus sativus seeds to determine the toxicity of RB-5 before and after treatment by S. cerevisiae. Results suggested that germination rate and the length of seeds radical irrigated with 0.15 g/L of RB-5 decreased by 30 and 53%, compared to those irrigated with treated solution. Therefore, metabolites derived from decolorization of RB-5 by S. cerevisiae X19G2 were significantly less toxic than the original dye.

Microbial decolorization of Reactive Black 5 dye by Bacillus albus DD1 isolated from textile water effluent: kinetic, thermodynamics & decolorization mechanism

Reactive Black 5 is one of the most widely used dye in textile and other industries. It is one of the significantly toxic azo dye which poses a serious threat to the environment when discharged into water bodies. A bacterial strain having potential to decolourise and degrade RB5 was isolated from textile effluent, and further identified and characterized. On the basis of morphological, biochemical, and 16s rRNA sequence analysis, the isolate was identified as Bacillus albus DD1. It showed 98% removal of RB5 from aqueous medium within 38 h under optimum parameters, pH 7, temperature 40 °C, in the presence of 1% yeast extract as a co-substrate, and 25% inoculum size at the initial dye concentration of 50 mg/l. Kinetic study revealed the decolorization reaction is a first order non- spontaneous reaction. The rate constant and reaction rate for RB5 decolourization in presence of the isolate was 0.0523 s⁻¹ and 2.6 × 10⁻³ mol/m³ sec, respectively. Values for ΔH and ΔS of the decolourization reaction, determined by thermodynamic analysis, were estimated to be +20.80 kJ/mol and ΔS = −0.1 kJ/mol K, respectively. LC-MS analysis revealed that decolorization was due to degradation of RB5 by cleavage of azo-bond by the bacterium, with the formation of s 3,6,8-trihyroxynapthalene and phthalic acid as degradation products. Therefore, the bacterium Bacillus albus DD1 has potential for application in biological treatment of dye contaminated industrial waste water.

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Bacterial strain Bacillus albus DD1 having potential to decolourise and degrade RB5 was isolated, identified and characterized.

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Effect of process parameters like pH, temperature, yeast extract as a co-substrate, inoculum size and initial dye concentration on the decolorization reaction was studied, the isolate showed growth and decolorization at alkaline pH 9 and 40 °C temperature, indicating its suitability for field application.

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More than 98% removal of RB5 was achieved within 38 h using the bacterial isolate, and a significant negative correlation existed between RB5 decolourization and bacterial growth.

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Bio-decolorization process followed the first order kinetics, rate constant and reaction rate for RB5 decolourization, was 0.0523 s⁻¹ and 2.6 × 10⁻³ mol/m³ sec, respectively.

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Reduction of azo bond and subsequent biodegradation of RB5 and were confirmed through LC-MS and 3,6,8-trihyroxynapthalene and phthalic acid were identified as degradation products.

Efficient reduction of reactive black 5 and Cr(Ⅵ) by a newly isolated bacterium of Ochrobactrum anthropi

It is important to obtain bacteria with the ability for reduction of dyes and Cr(Ⅵ) since dyes and Cr(Ⅵ) are often co-exist in textile wastewater. In this study, a new strain belonging to Ochrobactrum anthropi was isolated from textile wastewater, and could efficiently reduce Reactive Black 5 (RB 5) and Cr(Ⅵ). The results showed the degradation efficiency of RB 5 could achieve 100% and reduction efficiency of Cr(Ⅵ) was up to 80% within 3 days at initial RB 5 and Cr(Ⅵ) concentration of 400 mg/L and 20 mg/L. Mn²⁺ and Cu²⁺ could enhance the removal of RB 5 and Cr(Ⅵ), respectively. Glycerin, as electron donor, improved reduction efficiencies of RB 5 and Cr(Ⅵ). In addition, reduction mechanisms were further investigated. The results demonstrated that decreasing of RB 5 and Cr(Ⅵ) concentration were mainly through extracellular bioreduction rather than by adsorption. The FTIR and XPS analyses revealed that the O‒H, C‒C and C‒H groups on the cell surface might be involved in the reduction of RB 5 and Cr(Ⅵ). The information gives useful insights into understanding of how the bacterium reduce RB 5 and Cr(Ⅵ). The results indicated that the strain had excellent application prospect for treating industrial wastewater.

Simultaneous cleanup of Reactive Black 5 and cadmium by a desert soil bacterium

Multi-contaminated industrial wastewaters pose serious environmental risks due to high toxicity and non-biodegradability. The work reported here evaluated the ability of Pseudomonas aeruginosa strain Gb30 isolated from desert soil to simultaneously remove cadmium (Cd) and Reactive Black 5 (RB5), both common contaminants in various industrial effluents. The strain was able to grow normally and decolorize 50 mg L^-1 RB5 within 24 h of incubation in the presence of 0.629 m mol L^-1 of Cd²⁺. In order to evaluate strain performance in RB5 detoxification, a cytotoxicity test using Human Embryonic Kidney cells (HEK293) was used. Cadmium removal from culture media was determined using atomic adsorption. Even in presence of (0.115 + 0.157 + 0.401 + 0.381) m mol L^-1, respectively, of Cr⁶⁺, Cd²⁺, Cu²⁺ and Zn²⁺ in the growth medium, strain Gb30 successfully removed 35% of RB5 and 44%, 36%, 59% and 97%, respectively, of introduced Zn²⁺, Cu²⁺, Cr⁶⁺ and Cd²⁺, simultaneously. In order to understand the mechanism of Cd removal used by P. aeruginosa strain Gb30, biosorption and bioaccumulation abilities were examined. The strain was preferentially biosorbing Cd on the cell surface, as opposed to intracellular bioaccumulation. Microscopic investigations using AFM, SEM and FTIR analysis of the bacterial biomass confirmed the presence of various structural features, which enabled the strain to interact with metal ions. The study suggests that Pseudomonas aeruginosa Gb30 is a potential candidate for bioremediation of textile effluents in the presence of complex dye-metal contamination.

Study of simultaneous bioremediation of mixed reactive dyes and Cr(VI) containing wastewater through designed experiments

Xenobiotic azo dyes and chromate (Cr(VI)) containing industrial wastewaters cause severe ecological problems. The present bioremediation study aims to treat wastewater containing Cr(VI) ions and mixed azo dyes (reactive red 21 (RR21) and reactive orange 16 (RO16)) by Pseudomonas aeruginosa 23N1. The process optimization of bioremediation is investigated using statistical designed experimental tool of response surface methodology. The ANOVA analysis is performed to evaluate optimal biodecolourization condition. This study shows that the amount of yeast extract has major influence on biodecolourization performance. The decolourization of individual RO16 and RR21 dye in presence of 60 mg/L of Cr(VI) ions is obtained as 88.5 ± 0.8 and 92.3 ± 0.7% for 100 and 150 mg/L initial dye concentrations, respectively. In this study, bacteria exhibit high Cr(VI) removal potential of ~ 99.1% against initial Cr(VI) concentration of 150 mg/L. The negative influence of Cr(VI) ions on biodecolourization is only noticed when initial Cr(VI) concentration in wastewater is found above 150 mg/L. The results reveal that bacteria studied here could be used to biodecolourize dyes even in high saline condition (> 6000 mg/L). The reduction of ~ 80% in American Dye Manufacturers Institute colour index value is achieved for mixed dyes solution containing 50 mg/L of both RR21 and RO16 dyes along with 50 mg/L Cr(VI) ions. Significant changes in the UV-visible and ATR-FTIR spectra are observed in treated water that confirms the biodegradation of dyes. Toxicity study with Vigna radiata reveals the non-toxicity of degraded metabolites and strain 23N1 is recommended as an effective bioremediation agent.