In vitro studies on degradation of synthetic dye mixture by Comamonas sp. VS-MH2 and evaluation of its efficacy using simulated microcosm

Evaluating efficacy of Pseudomonas sp. EN-4 to lower the toxic potential of 4-bromophenol and assessing its competency in simulated microcosm

An indigenous bacterium Pseudomonas sp. EN-4 had been reported earlier for its ability to co-metabolise 4-bromophenol (4-BP), in presence of phenol (100 mg/L) as co-substrate. The present study was undertaken to validate the efficacy of biotransformation by comparing the toxicity profiles of untreated and EN-4 transformed samples of 4-BP, using both plant and animal model. The toxicity studies in Allium cepa (A. cepa) indicated to lowering of mitotic index (MI) from 12.77% (water) to 3.33% in A. cepa bulbs exposed to 4-BP + phenol, which reflects the cytotoxic nature of these compounds. However, the MI value significantly improves to 11.36% in its biologically treated counterpart, indicating normal cell growth. This was further supported by significant reduction in chromosomal aberrations in A. cepa root cells exposed to biologically treated samples of 4-BP as compared to untreated controls. The oxidative stress assessed by comparing the activity profiles of different marker enzymes showed that the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) were reduced by 56%, 72%, and 37% respectively, in EN-4 transformed samples of 4-BP + phenol compared to its untreated counterpart. Similar trends were evident in the comet assay of fish (Channa punctatus) blood cells exposed to untreated and biologically treated samples of 4-BP. The comparative studies showed significant reduction in tail length (72.70%) and % tail intensity (56.15%) in fish blood cells exposed to EN-4 treated 4-BP + phenol, compared to its untreated counterpart. The soil microcosm studies validated the competency of the EN-4 cells to establish and transform 4-BP in soil polluted with 4-BP (20 mg/kg) and 4-BP + phenol (20 + 100 mg/kg). The isolate EN-4 achieved 98.08% transformation of 4-BP in non-sterile microcosm supplemented with phenol, indicating to potential of EN-4 cells to establish along with indigenous microflora.

Synergistic role of bacterial consortium to biodegrade toxic dyes containing wastewater and its simultaneous reuse as an added value

The current environmental research has fascinated the sustainable exploitation of mix bacterial consortium to biodegrade the environmentally-related toxic compounds, including hazardous synthetic dyes. Based on the existing literature evidence, textile and other industrial waste effluents pollute the natural water bodies. Textile effluent contains synthetic dyes which are liberated in the environment without proper treatment. The presence of toxic dyes added to the textile effluents undoubtedly affects the flora and fauna as that untreated water is used for irrigation by local farmers. Many conventional and biological methods are in action for the treatment of wastewater. Physical and chemical processes are expensive as compared to microbial treatments. The use of microbial consortia generates efficient results. Wastewater is a valuable resource, however, up to 80% of wastewater is released to different water matrices. This discernment needs to change for a better tomorrow. In this context, herein, we present a robust microbial-assisted treatment and simultaneously reuse of the treated wastewater as an added value to induce plant growth. Thus, the microbial approach for textile waste treatment release by-product after degradation should be non-toxic for the environment. In the present study, the toxicity of synthetic textile dye named Reactive Red 120, Reactive Orange 122, Reactive Yellow 160, and Reactive Blue 19 was investigated using a bioassay method with plant species namely Sorghum bicolor. Plate and Pot experiment was conducted with respect to untreated Azo dyes, degraded metabolites obtained from single bacteria, and consortium. Efficient Seed germination (89%), shoot length (12.4 cm), root length (15.6 cm) of the plants were observed for bacterial consortium degraded metabolites exposed seeds after comparing with the control. The degraded metabolite also increases protein (45.56 mg/g) and sugar (3.15 mg/g) contents. Bioremediation of various textile industrial effluents saves the ecosystem from the harmful effects of hazardous dyes. The biological decolorization of the textile azo dyes was investigated under co-metabolic conditions. The degraded metabolites can be used to enhance crop productivity and for commercial application. This mandates the current and future research to develop economically feasible and environmentally sustainable wastewater treatment practices.

Biological detoxification and decolorization enhancement of azo dye by introducing natural electron mediators in MFCs

Reactive red 2 (RR2) is a highly recalcitrant and toxic azo dye that can cause the collapse of biological treatment system. Although MFC can decolorize RR2 effectively, its performance is still inevitably affected by toxicity. Anthraquinone can enhance MFCs' performance through mediating electron transfer. In this study, an anthraquinone-rich natural plants (B.rheum (Rheum offcinale Baill)) was extracted and then added to MFCs. The optimal dosage was selected and the enhanced effects were investigated. The results showed that adding 5%(V/V) extract resulted in the optimal performance elevation of MFC. When 5% extract was added together with RR2, 15.63% and 1.33-fold improvement in RR2 decolorization efficiency and rate were achieved compared with the control group. Meanwhile, higher power density (2.75 W/m³), coulombic efficiency (6.45%), and lower internal resistance (233.69 Ω) were also observed when 5% B.rheum extract and RR2 were added. B.rheum extract in MFCs enhanced microbial activity and enriched the dye-degrading microorganisms, such as Enterobacter, Raoultella, Comamonas and Shinella. B.rheum extract acts as "antidote" in alleviating the biotoxicity of RR2 was firstly illustrated in this study. The results provided a new strategy for using plant-source electron mediators to simultaneously improve biological detoxification, bioelectricity generation and dye decolorization in bioelectrochemical system.

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.

Cultivation of granules containing anaerobic decolorization and aerobic degradation cultures for the complete mineralization of azo dyes in wastewater

Granules which could efficiently mineralize azo dyes were cultivated through immobilization of aerobic degradation strains in a core composed of anaerobic decolorization cultures. The core was obtained in a up-flow anaerobic sludge blanket (UASB) reactor incubated with anaerobic decolorization bacteria. Aerobic degradation strains were then grown on the surface of the anaerobic core in a sequencing batch reactor (SBR). Three of the granules' surface layers demonstrated the occurrence of immobilization. The granulation process was monitored with 16S rDNA high throughput sequencing. Anaerobic decolorization cultures belonging to the genera of unclassified, Levilinea, and Petrimonas and the aerobic degradation genera of Thauera, unclassified, Thermomonas, and Ottowia were successfully fixed in the granules. The obtained granules were capable of decolorizing azo dyes under anaerobic situation, and the generated aromatic amines were then completely mineralized in aerated environment. Comparative studies on the relationship between removed contaminates and typical components concentrations in low to high strength azo dye wastewater showed that the granules have great potentials in treating wastewater with different complexity. The removal efficiency of COD and TOC was not restricted by loading concentrations.

Waste shrimp shell-derived hydrochar as an emergent material for methyl orange removal in aqueous solutions

Shrimp processing and consumption generate large amounts of waste shrimp shell (WSS) rich in chitin and protein. Herein, we successfully synthesized WSS-based hydrochar (WSH) adsorbent through deproteinization and deacetylation followed by hydrothermal carbonization (HTC) and acid washing. For comparison, another hydrochar (CCH) adsorbent was synthesized from HTC of commercial chitosan under identical conditions. Specifically, WSH contained rich nitrogen-containing functional groups with a long aliphatic chains structure. Acid etching of calcium carbonate in WSS led to a higher specific surface area of WSH (12.65 m²/g) which was nearly 6 times higher than that of CCH (2.13 m²/g). The lower deacetylation degree of WSH was responsible for higher amide I and amino groups retained therein. Under an optimal initial solution pH of 4.0, WSH could rapidly achieve a superb adsorption capacity of 755.08 mg/g for methyl orange molecule. Moreover, the adsorption process followed a pseudo-second-order kinetics model and was well described by a monolayer adsorption pattern based on the Langmuir isotherm model with correlation coefficients higher than 0.9989. Prominent adsorption performance of WSH for methyl orange was mainly attributed to electrostatic interactions, while steric hindrance effect had a detrimental impact on the adsorption capacity of CCH. Superb adsorption capacity and excellent regeneration performance suggest WSH could be a promising and affordable adsorbent candidate for anionic dye removal.

Microaerophilic biodegradation of raw textile effluent by synergistic activity of bacterial community DR4

Treatment of raw textile effluent (RTE) is very difficult, due to its inherent heterogeneous, low-biodegradable and toxic compositions. Pure and mixed microbial cultures have limited metabolic capabilities in effective mineralization of complex RTE. Therefore, in this study a novel bacterial community DR4 was enriched directly into a complex RTE consisting of 27 different dyes using textile dye polluted soil as an inoculum. The rigorous enrichment process resulted in acclimatization of a taxonomically distinct bacterial population, with an abundance of the genus Comamonas in the bacterial community DR4 as compared to the abundance of Pseudomonas in the RTE respectively, as revealed by high-throughput 16S rRNA gene (V3-V4 region) sequencing. Microaerophilic treatment of RTE by enriched bacterial community DR4, in the presence of optimized electron donor (sucrose) and nitrogen source (yeast extract) resulted in 88% of American Dye Manufacturer's Institute (ADMI) removal and 98% of Chemical oxygen demand (COD) reduction within 32 h at 37 °C. In silico prediction of the functional genes within bacterial community DR4 was made by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis. The PICRUSt analysis revealed high abundance of xenobiotic degradation and metabolism genes. The predicted functional genes and textile dye degradation pathways were further validated using Ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared (FTIR) spectroscopy and High Resolution Liquid Chromatography coupled with Mass Spectrometry (HR-LCMS) based characterization of textile dye degradation metabolites. The activity of azoreductases in the cell-free extracts (CFE) of the enriched bacterial community DR4 was induced by 1.83-7.81 folds in the presence of representative textile dyes as compared to uninduced samples, which confirmed their role in textile effluent decolourization. The degradation of four representative azo dyes present in RTE such as Disperse orange 30, Reactive red 152, Direct blue 2 and Acid brown 15 depicted symmetric degradation of azo bonds by bacterial community DR4.

Performances and structures of functional microbial communities in the mono azo dye decolorization and mineralization stages

Removal of azo dye from wastewater with biological method is a complicated process, including decolorization and mineralization. However, there is little understanding of the functional microbial community involved in the whole dye degradation process. In this study, a simplified model using anaerobic³-oxic²-sedimentaion reactor was proposed. Acid Orange and Methyl Orange were treated as model azo dyes. In each compartment, the degradation intermediates of azo dyes were identified with UV-Vis, FTIR, HPLC-MS and GC-MS, and the corresponding microorganisms were determined with 16S rDNA high throughput Miseq sequencing. Decolorization happened in anaerobic compartments, while mineralization of the resulted aromatic amines mainly occurred under aerobic circumstance. LEfSe analysis demonstrated that the microbial community compositions were significantly influenced by the chemical structures of substrates. With t-value biplot, the relationship between azo dye degradation and microbial community structure was proposed statistically. It was found that the functional microbial communities varied with the change of azo dye degradation intermediates. Besides, cleavage of benzene ring also happened under anaerobic circumstance. This may be due to the genera of Parabacteroides and Bacteroides, which exhibited significantly positive relationships with 1,4-Benzenediol. With the new model, the performances and structures of functional microbial communities for NN- reduction and aromatic amines mineralization were characterized and the reaction mechanism was explored.

Degradation of Chrysene by Enriched Bacterial Consortium

Chrysene is a high molecular weight (HMW), polycyclic aromatic hydrocarbon (PAH) known for its recalcitrance and carcinogenic properties and sparsely soluble (0.003 mg/L) in aqueous medium. Due to these refractory properties, bioavailability of chrysene is very low and therefore is persistence in the environment escaping the metabolism by microorganisms. However, few bacterial and fungal strains are reported to degrade chrysene, but with lower efficiency, requiring additional/extraneous carbon sources (co-substrates) for it’s complete mineralization. In this study, development, enrichment and characterization of bacterial consortium ASDC, consisting of Rhodococcus sp., ASDC1; Bacillus sp. ASDC2; and Burkholderia sp. ASDC3 were reported. Chrysene was utilized as a sole source of carbon and energy by the consortium, having maximum degradation rate of 1.5 mg/L/day and maximum growth rate of 0.125/h, under optimized conditions of pH 7.0, 37°C under aeration of 150 rpm on gyrating shaking. Chrysene degradation was unaffected in presence of other PAHs like pyrene, fluoranthene, naphthalene, phenanthrene, benzene, toluene and xylene, individually as well as in mixture. The results revealed that peptone, ammonium nitrate, sodium succinate have enhanced the chrysene degradation rate during first 24 h of experimentation, which was later on inhibited with increase in incubation time. The chrysene degradation was inhibited by mercury even at lower concentration (1 mM). The results also revealed that SDS has enhanced its degradation by 5.2-fold for initial 24 h of growth, but with increasing in the incubation period, it decreases by 1.2-fold on 7^th day of experimentation. The HPLC studies suggested that chrysene was degraded through phthalic acid pathway by the consortium ASDC and the stoichiometric measurements indicated the complete mineralization of chrysene. The flask scale results were validated at simulated microcosm models, where enriched consortium ASDC exhibited maximum degradation (96%) in polluted, non-sterile soil sediment, indicating that consortial strains along with indigenous metabolism showed synergistic metabolism for degradation of chrysene. Thus, the above study revealed the useful enrichment of bacterial community for synergistic degradation of PAHs (chrysene) which could be further exploited for in situ remediation of PAH contaminated sites.

Metabolism of pyrene through phthalic acid pathway by enriched bacterial consortium composed of Pseudomonas, Burkholderia, and Rhodococcus (PBR)

Polycyclic aromatic hydrocarbons (PAHs) are highly recalcitrant compounds due to their high hydrophobicity and tendency to partition in organic phase of soils. Pyrene is a high-molecular weight PAH, which has human health concerns. In the present study, a bacterial consortium, PBR, was developed from a long-term polluted site, viz., Amlakhadi, Ankleshwar, Gujarat, for effective degradation of pyrene. The consortium effectively metabolized pyrene as a sole source of carbon and energy. The consortium comprised three bacterial species, Pseudomonas sp. ASDP1, Burkholderia sp. ASDP2, and Rhodococcus sp. ASDP3. The maximum growth rate of consortium was 0.060/h and the maximum pyrene degradation rate was 16 mg/l/day. The organic and inorganic nutrients along with different surfactants did not affect pyrene degradation, but degradation rate moderately increased in the presence of sodium succinate. The significant characteristic of the consortium was that it possessed an ability to degrade six other hydrocarbons, both independently and simultaneously at 37 °C, in BHM (pH 7.0) under shaking conditions (150 rpm) and it showed resistance towards mercury at 10 mM concentration. Phthalic acid as one of the intermediates during pyrene degradation was detected through high-performance liquid chromatography (HPLC). The efficiency of consortium for pyrene degradation was validated in simulated microcosms’ study, which indicated that 99% of pyrene was metabolized by the consortium under ambient conditions.

Biodegradation of Navy N5RL1 carpet dye by Staphylococcus saprophyticus strain BHUSS X3

Biodegradation of Navy N5RL1, a widely used acidic azo dye in carpet industry, was studied by bacterial strain isolated from the dye-contaminated soil collected from a carpet industry premises located in Bhadohi, Sant Ravidas Nagar and Uttar Pradesh, India. The isolated strain was identified as Staphylococcus saprophyticus BHUSS X3 on the basis of morphological, biochemical and 16S rRNA gene sequencing analysis. The strain BHUSS X3 decolorized 95.7 % of dye (100 mg/l) within 6 h at optimum pH 8, temperature 35 °C, inoculum 4.0 % under static condition during 24 h incubation. The isolated bacterial strain BHUSS X3 can toralate dye concentration upto 1,000 mg/l. The dye degradation metabolites were confirmed by analysis of degraded products using UV-Vis spectrophotometric, HPLC and FTIR technique. The phytotoxicity analysis was also conducted on Phaseolus aureus and enhanced seed germination was recorded.

Co-metabolic degradation of diazo dye- reactive blue 160 by enriched mixed cultures BDN

Mixed cultures BDN (BDN) proficient in decolourizing diazo dye-reactive blue 160 (RB160) consist of eight bacterial strains, was developed through culture enrichment method from soil samples contaminated with anthropogenic activities. The synthrophic interactions of BDN have led to complete decolourization and degradation of RB160 (100mg/L) within 4h along with co-metabolism of yeast extract (0.5%) in minimal medium. BDN microaerophilicaly decolourized even 1500mg/L of RB160 under high saline conditions (20g/L NaCl) at 37°C and pH 7.0. BDN exhibited broad substrate specificity and decolourized 27 structurally different dyes. The reductase enzymes symmetrically cleaved RB160 and oxidative enzymes further metabolised the degraded products and five different intermediates were identified using FTIR, (1)HNMR and GC-MS. The phytotoxicity assay confirmed that intact RB160 was more toxic than dye degraded intermediates. The BDN was able to colonize and decolourized RB160 in soil model system in presence of indigenous miocroflora as well as in sterile soil without any amendment of additional nutrients, which signifies it useful and potential application in bioremediation.

Evaluation of in vitro efficacy for decolorization and degradation of commercial azo dye RB-B by Morganella sp. HK-1 isolated from dye contaminated industrial landfill

Reactive Black-B (RB-B) - one of the multi-sulphonated reactive azo dye - is being used extensively in textile as well as paper industries. Reactive azo dyes comprise of a significant group of synthetic compounds categorized as xenobiotics and its abatement from the environment still remains a challenge. In the present study, a newly isolated indigenous bacterial strain Morganella sp. HK-1 was exploited for its ability to decolorize and degrade RB-B dye. The isolate completely degraded RB-B (20 g L(-1)) within 24h under static conditions. Furthermore, the visible and FTIR spectral analysis established the bio-degradation of RB-B. The degraded metabolites of RB-B by Morganella sp. HK-1 were identified by GC-MS analysis as disodium 3,4,6-triamino-5-hydroxynaphthalene-2,7-disulfonate, 4-aminophenylsulfonylethyl hydrogen sulfate, naphthalene-1-ol, aniline and benzene. Based on this information, a putative pathway of degradation of RB-B by Morganella sp. HK-1 has been proposed. This study is the first report on elucidation of mechanism of bacterial degradation of RB-B dye. Furthermore, phytotoxicity, genotoxicity and aquatic acute toxicity studies of the parent dye and the bio-degraded dye products revealed drastic reduction in the toxicity of metabolites as compared to the parent dye. This implies that the biotreatment of the dye is of non-toxic nature. This study thus indicates the effectiveness of Morganella sp. HK-1 for the treatment of textile effluents containing sulphonated azo dyes.