Polyol synthesis of one-dimensional Ag nanowires for the photocatalytic degradation of textile dye and effective removal of microbes.

Due to the excess release of hazardous pollutants to the environment, the quest for the synthesis of effective nanomaterials for wastewater treatment is never-ending. Present study reports the polyol synthesis of Ag NWs of ~ 85 nm diameter and average length of 4.08 µm using PVP and ethylene glycol. The experimental data on the methylene blue dye degradation substantiated the photocatalytic efficiency of Ag NWs (88% degradation in 120 min). Furthermore, the Ag NWs exhibited microbial load reducing property in air conditioner condensate water (ACW) within a time period of 60 min. Also, the anti-bacterial effect of Ag NWs was estimated using two human pathogenic bacterial strains, namely Staphylococcus aureus and Bacillus cereus. The antibacterial potential of Ag NWs against Staphylococcus aureus and Bacillus cereus was revealed significant with an inhibition zone size of 14 ± 0.1 mm and 9 ± 0.1 mm, respectively. Hence, the present work validates the potential efficiency of Ag NWs in the degradation of textile dyes and reduction of microbial population.

Degradation and detoxification of reactive yellow dyes by Scedosporium apiospermum: a mycoremedial approach.

Textile industrial effluents have long enunciated the essentiality of ascertaining an efficient wastewater treatment for the removal of azo dyes given their potential disturbances on the ecosystem. Our study investigated the efficiency of the strain SKF2 among 14 other isolates, molecularly identified to be Scedosporium apiospermum, isolated by our research group from the textile effluent sludge in the degradation of two azo dyes, Reactive Yellow 145 and Remazol Yellow RR. Kinetic profiling of the degradation process revealed the decolourisation efficiency to be 94.8 and 86.9% for RY 145 and RYRR, respectively, during the declining growth phase. Laccase and polyphenol oxidase (RY 145-2.37 and RYRR-2.30 U/mL; RY 145-3.26 and RYRR-2.89 U/mL, respectively) were found to influence the biodegradation process in both the dyes than the other examined fungal degradative enzymes. The metabolic pathway predicted with the aid of GC-MS analysis identified the degraded metabolites to be smaller molecular weight non-toxic products. Assessment of toxicity via brine shrimp lethality assay (RY 145-23.3% and RYRR-16.7%, respectively) and seed germination assay (RY 145-96.7% and RYRR-83.3%) further solidified the detoxified status of both the dyes after biodegradation. The experimental data thus substantiated the expediency of S. apiospermum SKF2 in the degradation of textile azo dyes and its further employment in the bioremediation of textile wastewaters for agricultural applications and ecological recycling.

Biodegradation of Reactive Red 198 by textile effluent adapted microbial strains.

A sustainable technology to eliminate the persistent reactive dyes from the textile effluents discharged indiscriminately in the environment is highly desirous given the explosive growth of textile industries. The present study investigated the potential of two different bacterial strains, Bacillus cereus SKB12 and Enterobacter hormaechei SKB16 isolated from the dye house effluent sludge in the biotransformation of Reactive Red 198 (RR 198). Process variables such as temperature, pH, shaking conditions and contact time were optimized for the successful decolourization of RR 198. Maximum decolourization of 80% and 85% of RR 198 was achieved at pH 6 and 7, and 40 °C in microaerophilic conditions on treatment with B. cereus and E. hormaechei, respectively. High-Performance Liquid Chromatography (HPLC), and Gas Chromatography-Mass Spectrometry (GC-MS) analyses conducted further affirmed that the decolourization of RR 198 was rather due to biodegradation than biosorption through shift in wavenumbers, retention time variations and the appearance of lesser molecular weight peaks. Degradative pathway for RR 198 predicted based on the enzyme assay data and dye degraded metabolite peaks acquired through GC-MS analysis highlighted the significance of azoreductase and laccase in the degradation of RR 198 into smaller non-toxic compounds. In addition, toxicity assessment through zootoxicological and phytotoxicological experiments using brine shrimp and Vigna radiata validated the detoxified status of the metabolites thus proving the promising potentials of the bacterial strains in the remediation of azo dyes.

Microbial degradation of azo dyes by textile effluent adapted, Enterobacter hormaechei under microaerophilic condition.

Landmark and sustainable eco-friendly dye treatment processes are highly desirous to ameliorate their effect on the environment. The present study investigated the azo dye degradation efficiency of adapted Enterobacter hormaechei SKB 16 from textile effluent polluted soil in optimized culture conditions. The adapted bacteria strain was identified by standard microbiological and molecular techniques. E. hormaechei was tested individually for the decolourizing of Reactive Yellow 145 (RY 145) and Reactive Red F3B (RR 180) dyes under optimized conditions of pH, temperature and dye concentration on decolourization were studied. The adapted bacteria strain exhibited maximum decolourization (98 %) of Reactive yellow 145 and Reactive red 180 in 100 ppm concentration at pH 7, temperature 37 °C after 98 h of incubation. The enzyme analyses revealed that azo reductase and laccase played major roles in the cleavage of the azo bond and desulfonation respectively of both dyes during degradation. The metabolites were further characterized by Fourier Transform Infrared Spectroscopy (FT-IR), High-Performance Liquid Chromatography (HPLC), and Gas Chromatography-Mass Spectrometry (GCMS). Thereafter, degradation was deduced based on changes of the functional group, variation in retention times and mass/charge ratio and molecular weight. This study elucidated the promising potentials of adapted SKB 16 strain in the eco-friendly removal of textile azo dyes. In addition, repeatability and sustainability are enhanced due to effective management of time which would have been spent on rigorous and extensive screening process.

Biodegradation of textile azo dyes by textile effluent non-adapted and adapted Aeromonas hydrophila.

Textile effluent discharged in water and soil have severe effects on living beings as well as environs worldwide. Pioneering, ecologically sustainable and economically viable treatment systems are urgently desired. This study investigated decolorization along with degradation of three azo dyes by non-adapted Aeromonas hydrophila MTCC 1739 and textile-effluent adapted Aeromonas hydrophila SK16 bacteria under optimized physicochemical conditions. UV-visible analysis (for decolorization percentage calculated using absorbance), FTIR (fourier transform infrared spectroscopy for functional group identification), HPLC (high performance liquid chromatography for degraded metabolites analysis based on retention time) and GC-MS (gas chromatography-mass spectrometry for proposing degradative pathways based on mass/charge as well as molecular weight) supported efficient biodegradation of these dyes into simpler metabolites by both cultures. Time taken for decolorization by the adapted strain was less but both were equally efficient in mineralizing dyes, utilizing them as energy source. Enzyme assays revealed over-expression of dye degrading enzymes in presence of toxic azo dyes. Thus, it is suggested that both adapted and non-adapted bacteria act as azo dye degraders with potential use in efficient and lucrative effluent treatment curbing expansive preliminary screening of autochthonous strains for azo dye degradation.

Synergistic effect of biological and advanced oxidation process treatment in the biodegradation of Remazol yellow RR dye.

The current study investigated the efficiency of synergistic biological and Advanced Oxidation Process (AOPs) treatment (B-AOPs) using Aeromonas hydrophila SK16 and AOPs-H2O2 in the removal of Remazol Yellow RR dye. Singly, A. hydrophila and AOPs showed 90 and 63.07% decolourization of Remazol Yellow RR dye (100 mg L-1) at pH 6 and ambient temperature within 9 h respectively. However, the synergistic B-AOPs treatments showed maximum decolorization of Remazol Yellow RR dye within 4 h. Furthermore, the synergistic treatment significantly reduced BOD and COD of the textile wastewater by 84.88 and 82.76% respectively. Increased levels in laccase, tyrosinase, veratryl alcohol oxidase, lignin peroxidase and azo reductase activities further affirmed the role played by enzymes during degradation of the dye. UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS) confirmed the biotransformation of dye. A metabolic pathway was proposed based on enzyme activities and metabolites obtained after GC-MS analysis. Therefore, this study affirmed the efficiency of combined biological and AOPs in the treatment of dyes and textile wastewaters in comparison with other methods.

Legacy of a Pleistocene bacterial community: Patterns in community dynamics through changing ecosystems.

Bacterial communities are resilient to the environmental changes, yet the effect of long term ecological changes on bacterial communities remain poorly explored. To study the effect of prolonged environmental changes, a 25 m long sediment core was excavated from a paleo beach ridge located on the Cauvery delta, south east coast of India. Geological evidences suggested that the site has experienced multiple marine transgressions and regressions. The three paleosols from Vettaikaraniruppu (VKI) beach ridge, VKI-2 (2.8 m bgl; 3 kybp), VKI-5 (7.2 m bgl; 6 kybp) and VKI-14 (24.5 m bgl; 146 kybp) was chosen for bacterial community analysis based on their formation period. Bacterial community structure of paleosols was reconstructed using V3 hypervariable region of bacterial 16S rDNA targeted Illumina sequencing. The VKI-5 sediment layer which formed under marine environment contained highest bacterial diversity, and the community was a mix up of terrestrial and marine bacterial population. The final community VKI-2 exhibited an approximate structural pattern witnessed in the native bacterial community VKI-14 which formed during marine regression. Furthermore, marine transgression and regression experienced in VKI resulted in the formation of distinct biogeographic patterns.

Application of docking and active site analysis for enzyme linked biodegradation of textile dyes.

Growth of textile industries led to production of enormous dye varieties. These textile dyes are largely used, chemically stable and easy to synthesize. But they are recalcitrant and persist as less biodegradable pollutants when discharged into waterbodies. Potential use of enzyme-linked bioremediation of textile dyes will control their toxicity in waterbodies. Bioinformatics and Molecular docking tool provides an insight into remediation mechanism by predicting susceptibility of dye degradation using oxidoreductive enzymes. In this study, six dyes, Reactive Red F3B, Remazol Red RGB, Joyfix Red RB, Joyfix Yellow MR, Remazol Blue RGB and Turquoise CL-5B of azo, anthraquinone and phthalocyanine molecular class were identified as potential targets for degradation by laccase and azoreductase of Aeromonas hydrophila in addition to Lysinibacillus sphaericus through in silico docking tool BioSolveIT-FlexX. Azoreductase breaks azo bonds by ping-pong mechanism whereas laccase decolorizes dyes by free radical mechanism which is not specific in nature. Results were analyzed based on parameters like stability, catalytic action and selectivity for enzyme-dye interactions. Amino acids of enzymes interacted with several dyes substantiating variations in active site for enzyme-ligand binding affinity. This suggests the role of enzymes in decolorizing an extensive variety of textile dyes, thereby, aiding in understanding the enzyme mechanisms in Bioremediation.