Assessment upon species evolution of mixed consortia for azo dye decolorization

Evaluating the potential of thermo-alkaliphilic microbial consortia for azo dye biodegradation under anaerobic-aerobic conditions: Optimization and microbial diversity analysis

Wastewaters in textile industry are mainly characterized by higher pH, color, salt and chemical oxygen demand (COD) values, which are environmentally undesirable. Among these textile effluent characteristics, color removal is the most challenging task. In this study, the potential of Rift Valley halotolerant and thermo-alkaliphilic microbial consortia (collected from Shala hot spring located in Ethiopia) for azo dye biodegradation under anaerobic-aerobic conditions were evaluated. Optimization and microbial diversity analysis were done using Reactive Red 141. Under optimum conditions of pH (9), temperature (55 °C), salinity (0.5%), and nutrients, microbial consortia can remove >98% color and 92.7 ± 7.3% COD under anaerobic and aerobic conditions, respectively. In addition, the consortia was capable of decolorizing initial dye concentrations of 100-1000 mg/L, and various dye types including Everzol Blue LX, RY 84, RR 239, RB 198 and RY 700. The 16S rRNA gene sequence results showed that Bacteroidetes (25.3%) > Proteobacteria (21.0%) > Chloroflexi (18.5%) > Halobacterota (6.2%) dominant phyla. Based on the findings, non-color effluent adapted Rift Valley halotolerant and thermo-alkaliphilic bacterial consortia can be a potential candidate for bioremediation of textile and other industries characterized by higher salinity, temperature and pH.

Enhanced degradation of anthraquinone dyes by microbial monoculture and developed consortium through the production of specific enzymes

The current study investigates the decolorization of Indanthrene Blue RS dye and the optimization of process parameters needed for effective decolorization by the bacterial consortium. The pure culture of strain TS8, PMS, and NCH has been isolated from the textile wastewater sample collected from local textile processing units outlet and dye contaminated soil from Odisha, India. A bacterial consortium-BP of Bacillus flexus TS8 (BF), Proteus mirabilis PMS (PM), and Pseudomonas aeruginosa NCH (PA) were developed. The physicochemical parameters were optimized to attain maximum decolorization efficacy. Degradation of Indanthrene Blue RS and the formation of metabolites were confirmed through UV-vis spectroscopy, FT-IR, and GC-MS analysis. The developed consortium-BP showed an enhanced decolorization of Indanthrene Blue RS dye with an Average decolorization rate of 11,088 µg h^-1 within 9 h compared to the individual strains under aerobic conditions. The supplementation of agricultural residual wastes showed increased decolorization efficiency of consortium-BP. Higher reduction in TOC and COD removal (≥ 80%) determined the mineralization of Indanthrene Blue RS by consortium-BP. Significant induction of various oxidoreductive enzymes in consortium-BP compared to that of Individual strains indicates their involvement in the overall decolorization and degradation process, with the higher protein concentration in the intracellular enzymes. Studies on the phytotoxicity effect revealed the non-toxic nature of the degraded products formed on mineralization of Indanthrene Blue RS by consortium-BP. This study represents a new approach for enhanced biodegradation using consortium-BP in treating textile wastewaters containing anthraquinone dyes.

Microbial use for azo dye degradation-a strategy for dye bioremediation

Azo dyes are aromatic compounds with one to many -N=N- groups as well as the leading class of synthetic dyes utilised in commercial solicitations. Azo dyes, released in the environment through textile effluents, have hazardous effects on the aquatic as well as human life. Their persistence and discharge into the environment are becoming a global concern; thus, the remediation of these contaminants has acquired great attention. The current review comprehensively discusses some of the main aspects of biodegradation of azo dyes. A variety of physicochemical approaches has already been utilised for treatment of textile effluents counting filtration, coagulation and chemical flocculation. Though these conventional techniques are effective, yet they are lavish and also comprise formation of concentrated sludge that makes a secondary disposal problem. In this regard, microbial usage is an effective, economical, bio-friendly and ecologically benign approach.

The Comparative Study on the Rapid Decolorization of Azo, Anthraquinone and Triphenylmethane Dyes by Anaerobic Sludge

An anaerobic sludge (AS), capable of decolorizing a variety of synthetic dyes, was acclimated and is reported here. The sludge presented a much better dye decolorizing ability than that of different individual strains. A broad spectrum of dyes could be decolorized by the sludge. Continuous decolorization tests showed that the sludge exhibited the ability to decolorize repeated additions of dye. The chemical oxygen demand (COD) removal rate of the dye wastewater reached 52% after 12 h of incubation. Polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) profiles revealed that the microbial community changed as a result of varying initial concentrations of dyes. Phylogenetic analysis indicated that microbial populations in the sludge belonged to the phyla Acidobacteria, Firmicutes, Bacteroidetes, Chloroflexi and Proteobacteria. The degradation products of the three types of dye were identified. For azo dyes, the anaerobic sludge converted Methyl Orange to N,N-dimethylbenzene-1,4-diamine and 4-aminobenzenesulfonic acid; for triphenylmethane dyes, after Malachite Green was decolorized, the analyzed products were found to be a mixture of N,N-dimethylbenzenamine, 3-dimethyl-aminophenol and 4-dimethylaminobenzophenone; for anthraquinone dyes, two products (acetophenone and 2-methylbenzoic acid) were observed after Reactive Blue 19 decolorization. Together, these results suggest that the anaerobic sludge has promising potential for use in the treatment of industrial wastewater containing various types of dyes.

Decolorization of synthetic brilliant green carpet industry dye through fungal co-culture technology

Aim of the present study was to evaluate the efficiency of fungal co-culture for the decolorization of synthetic brilliant green carpet industry dye. For this purpose two lignocellulolytic fungi Pleurotus florida (PF) and Rhizoctonia solani (RS) were employed. The study includes determination of enzyme profiles (laccase and peroxidase), dye decolorization efficiency of co-culture and crude enzyme extracts. Both fungi produced laccase and Mn peroxidase and successfully decolorized solutions of different concentrations (2.0, 4.0, 6.0, & 8.0(w/v) of dye. The co-culture resulted highest 98.54% dye decolorization at 2% (w/v) of dye as compared to monocultures (82.12% with PF and 68.89% with RS) during 12 days of submerged fermentation. The lower levels of dyes were rapidly decolorized, while higher levels in slow order as 87.67% decolorization of 8% dye. The promising achievement of the study was remarkable decolorizing efficiency of co-culture over monocultures. The direct treatment of the mono and co-culture enzyme extracts to dye also influenced remarkable. The highest enzymatic decolorization was through combined (PF and RS) extracts, while lesser by monoculture extracts. Based on the observations and potentiality of co-culture technology; further it can be exploited for the bioremediation of areas contaminated with hazardous environmental pollutants including textile and other industry effluents.

Improved biodegradation of textile dye effluent by coculture

The present study demonstrates the de-colorization and degradation of textile effluent by coculture consisting of three bacterial species isolated from textile effluent contaminated environment with an aim to reduce the treatment time. The isolates were identified as Ochrobactrum sp., Pseudomonas aeruginosa and Providencia vermicola by 16S rRNA analysis. Their secondary structure was predicted and GC content of the sequence was found to be 54.39, 52.10, and 52.53%. The co-culture showed a prominent increase in the degradation activity due to the action of oxidoreductase enzymatic mechanism of laccase, NADH-DCIP reductase and azoreductase activity. The biodegradability index of 0.75 was achieved with 95% chemical oxygen demand (COD) reduction in 16 h and 78 and 85% reduction in total organic carbon (TOC) and total solids was observed. Bioaccumulation of metals was identified by X-ray diffraction (XRD) analysis. The effective decolorization was confirmed from the results of UV-vis spectroscopy, high performance liquid chromatography and Fourier transformed infrared spectrometer analyzes. The possible degradation pathway was obtained from the analysis of liquid chromatography-mass spectroscopy analysis and the metabolites such as 2-amino naphthalene and N-phenyl-1.3,5 triazine were observed. The toxic nature of the effluent was analyzed using phyto-toxicity, cell-death assay and geno-toxicity tests.

Decolorization of dye Reactive Black 5 by newly isolated thermophilic microorganisms from geothermal sites in Galicia (Spain)

In this study, thermophilic microbial strains from thermal spots in northwestern Spain displaying excellent decolorization capability were isolated. The research work tackled: (i) the ability of consortia to degrade a model di-azo dye Reactive Black at different pHs in flask cultures, obtaining that just neutral pHs licensed degradation levels near to 70%, (ii) the isolation of tree of the bacteria, which rendered possible reaching high levels of decolorization (80%) after just 24 h in aerobic conditions, and which were identified through 16S rRNA sequencing to possess high homology (99%) with Anoxybacillus pushchinoensis, Anoxybacillus kamchatkensis and Anoxybacillus flavithermus, and (iii) the cultivation of the isolates in a bench-scale bioreactor, which led to a decolorization rate two-fold higher than that obtained in flask cultures. Therefore, this work makes up the first time that a decolorization process of an azo dye by thermophilic microorganisms in aerobic conditions is investigated.

Decolorization and biodegradation of reactive dyes and dye wastewater by a developed bacterial consortium

A bacterial consortium (consortium GR) consisting of Proteus vulgaris NCIM-2027 and Micrococcus glutamicus NCIM-2168 could rapidly decolorize and degrade commonly-used sulfonated reactive dye Green HE4BD and many other reactive dyes. Consortium GR shows markedly higher decolorization activity than that of the individual strains. The preferable physicochemical parameters were identified to achieve higher dye degradation and decolorization efficiency. The supplementation of cheap co-substrates (e.g., extracts of agricultural wastes) could enhance the decolorization performance of consortium GR. Extent of mineralization was determined with TOC and COD measurements, showing nearly complete mineralization of Green HE4BD by consortium GR (up to 90% TOC and COD reduction) within 24 h. Oxidoreductive enzymes seemed to be involved in fast decolorization/degradation process with the evidence of enzymes induction in the bacterial consortium. Phytotoxicity and microbial toxicity studies confirm that the biodegraded products of Green HE4BD by consortium GR are non-toxic. Consortium GR also shows significant biodegradation and decolorization activities for mixture of reactive dyes as well as the effluent from actual dye manufacturing industry. This confers the possibility of applying consortium GR for the treatment of industrial wastewaters containing dye pollutants.