Azoreductase activity of dye-decolorizing bacteria isolated from the human gut microbiota

Sequence similarity network analysis of drug- and dye-modifying azoreductase enzymes found in the human gut microbiome

Drug metabolism by human gut microbes is often exemplified by azo bond reduction in the anticolitic prodrug sulfasalazine. Azoreductase activity is often found in incubations with cell cultures or ex vivo gut microbiome samples and contributes to the xenobiotic metabolism of drugs and food additives. Applying metagenomic studies to personalized medicine requires knowledge of the genes responsible for sulfasalazine and other drug metabolism, and candidate genes and proteins for drug modifications are understudied. A representative gut-abundant azoreductase from Anaerotignum lactatifermentan DSM 14214 efficiently reduces sulfasalazine and another drug, phenazopyridine, but could not reduce all azo-bonded drugs in this class. We used enzyme kinetics to characterize this enzyme for its NADH-dependent reduction of these drugs and food additives and performed computational docking to provide the groundwork for understanding substrate specificity in this family. We performed an analysis of the Flavodoxin-like fold InterPro family (IPR003680) by computing a sequence similarity network to classify distinct subgroups of the family and then performed chemically-guided functional profiling to identify proteins that are abundant in the NIH Human Microbiome Project dataset. This strategy aims to reduce the number of unique azoreductases needed to characterize one protein family in the diverse set of potential drug- and dye-modifying activities found in the human gut microbiome.

Isolation, molecular identification, and genomic analysis of Mangrovibacter phragmitis strain ASIOC01 from activated sludge harboring the bioremediation prowess of glycerol and organic pollutants in high-salinity

The physiological and genotypic characteristics of Mangrovibacter (MGB) remain largely unexplored, including their distribution and abundance within ecosystems. M. phragmitis (MPH) ASIOC01 was successfully isolated from activated sludge (AS), which was pre-enriched by adding 1,3-dichloro-2-propanol and 3-chloro-1,2-propanediol as carbon sources. The new isolate, MPH ASIOC01, exhibited resilience in a medium containing sodium chloride concentration up to 11% (with optimal growth observed at 3%) and effectively utilizing glycerol as their sole carbon source. However, species delimitation of MGBs remains challenging due to high 16S rRNA sequence similarity (greater than 99% ANI) among different MGBs. In contrast, among the housekeeping gene discrepancies, the tryptophan synthase beta chain gene can serve as a robust marker for fast species delimitation among MGBs. Furthermore, the complete genome of MPH ASIOC01 was fully sequenced and circlized as a single contig using the PacBio HiFi sequencing method. Comparative genomics revealed genes potentially associated with various phenotypic features of MGBs, such as nitrogen-fixing, phosphate-solubilizing, cellulose-digesting, Cr-reducing, and salt tolerance. Computational analysis suggested that MPH ASIOC01 may have undergone horizontal gene transfer events, possibly contributing unique traits such as antibiotic resistance. Finally, our findings also disclosed that the introduction of MPH ASIOC01 into AS can assist in the remediation of wastewater chemical oxygen demand, which was evaluated using gas chromatograph-mass spectrometry. To the best of our knowledge, this study offers the most comprehensive understanding of the phenotypic and genotypic features of MGBs to date.

Gut microbial β-glucuronidases influence endobiotic homeostasis and are modulated by diverse therapeutics

Hormones and neurotransmitters are essential to homeostasis, and their disruptions are connected to diseases ranging from cancer to anxiety. The differential reactivation of endobiotic glucuronides by gut microbial β-glucuronidase (GUS) enzymes may influence interindividual differences in the onset and treatment of disease. Using multi-omic, in vitro, and in vivo approaches, we show that germ-free mice have reduced levels of active endobiotics and that distinct gut microbial Loop 1 and FMN GUS enzymes drive hormone and neurotransmitter reactivation. We demonstrate that a range of FDA-approved drugs prevent this reactivation by intercepting the catalytic cycle of the enzymes in a conserved fashion. Finally, we find that inhibiting GUS in conventional mice reduces free serotonin and increases its inactive glucuronide in the serum and intestines. Our results illuminate the indispensability of gut microbial enzymes in sustaining endobiotic homeostasis and indicate that therapeutic disruptions of this metabolism promote interindividual response variabilities.

Hues of risk: investigating genotoxicity and environmental impacts of azo textile dyes

The textile industry, with its extensive use of dyes and chemicals, stands out as a significant source of water pollution. Exposure to certain textile dyes, such as azo dyes and their breakdown products like aromatic amines, has been associated with health concerns like skin sensitization, allergic reactions, and even cancer in humans. Annually, the worldwide production of synthetic dyes approximates 7 × 107 tons, of which the textile industry accounts for over 10,000 tons. Inefficient dyeing procedures result in the discharge of 15-50% of azo dyes, which do not adequately bind to fibers, into wastewater. This review delves into the genotoxic impact of azo dyes, prevalent in the textile industry, on aquatic ecosystems and human health. Examining different families of textile dye which contain azo group in their structure such as Sudan I and Sudan III Sudan IV, Basic Red 51, Basic Violet 14, Disperse Yellow 7, Congo Red, Acid Red 26, and Acid Blue 113 reveals their carcinogenic potential, which may affect both industrial workers and aquatic life. Genotoxic and carcinogenic characteristics, chromosomal abnormalities, induced physiological and neurobehavioral changes, and disruptions to spermatogenesis are evident, underscoring the harmful effects of these dyes. The review calls for comprehensive investigations into the toxic profile of azo dyes, providing essential insights to safeguard the aquatic ecosystem and human well-being. The importance of effective effluent treatment systems is underscored to mitigate adverse impacts on agricultural lands, water resources, and the environment, particularly in regions heavily reliant on wastewater irrigation for food production.

Sunset Yellow dye effects on gut microbiota, intestinal integrity, and the induction of inflammasomopathy with pyroptotic signaling in male Wistar rats

Although concern persists regarding possible adverse effects of consumption of synthetic azo food dyes, the mechanisms of any such effects remain unclear. We have tested the hypothesis that chronic consumption of the food dye Sunset Yellow (SY) perturbs the composition of the gut microbiota and alters gut integrity. Male rats were administered SY orally for 12 weeks. Analysis of fecal samples before and after dye administration demonstrated SY-induced microbiome dysbiosis. SY treatment reduced the abundance of beneficial taxa such as Treponema 2, Anaerobiospirillum, Helicobacter, Rikenellaceae RC9 gut group, and Prevotellaceae UCG-003, while increasing the abundance of the potentially pathogenic microorganisms Prevotella 2 and Oribacterium. Dysbiosis disrupted gut integrity, altering the jejunal adherens junction complex E-cadherin/β-catenin and decreasing Trefoil Factor (TFF)-3. SY administration elevated LPS serum levels, activated the inflammatory inflammasome cascade TLR4/NLRP3/ASC/cleaved-activated caspase-1 to mature IL-1β and IL-18, and activated caspase-11 and gasdermin-N, indicating pyroptosis and increased intestinal permeability. The possibility that consumption of SY by humans could have effects similar to those that we have observed in rats should be examined.

Biodegradation of commercial textile reactive dye mixtures by industrial effluent adapted bacterial consortium VITPBC6: a potential technique for treating textile effluents

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; Vmax and Km values of the enzyme catalyzed five-dye decolorization were 128.88 mg L-1 day-1 and 1003.226 mg L-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Dual stimuli-responsive delivery system for self-regulated colon-targeted delivery of poorly water-soluble drugs

Inflammatory bowel disease (IBD) are chronic inflammatory conditions which cause significant patient morbidity. Local drug delivery to the colon can improve treatment efficacy and reduce side effects associated with IBD treatment. Smart drug delivery systems are designed to regulate the release of therapeutic agents at the desired site of action. pH-responsive drug carriers have been previously utilised for improved oral drug delivery beyond stomach harsh conditions. Additionally, the colon possesses a diverse microbiome secreting bioactive molecules e.g., enzymes, that can be exploited for targeted drug delivery. We herein synthesised and characterised a 2-hydroxyethyl methacrylate and methacrylic acid copolymer, crosslinked with an azobenzyl crosslinker, that displayed pH- and enzyme-responsive properties. The swelling and drug release from hydrogel were analysed in pH 1.2, 6.5 and 7.4 buffers, and in the presence of rat caecal matter using metronidazole and mesalamine as model BCS Class I and IV drugs, respectively. Swelling studies displayed pH-responsive swelling behaviour, where swelling was maximum at pH 7.4 and minimum at pH 1.2 (69 % versus 32 %). Consequently, drug release was limited in gastric and small intestinal conditions but increased significantly when exposed to colonic conditions containing caecal matter. This system displays promising capacity for achieving colon-targeted drug delivery with enhanced dissolution of poorly water-soluble drugs for local treatment of IBD and other colon-targeted therapies.

Microbial metabolites as modulators of host physiology

The gut microbiota is increasingly recognised as a key player in influencing human health and changes in the gut microbiota have been strongly linked with many non-communicable conditions in humans such as type 2 diabetes, obesity and cardiovascular disease. However, characterising the molecular mechanisms that underpin these associations remains an important challenge for researchers. The gut microbiota is a complex microbial community that acts as a metabolic interface to transform ingested food (and other xenobiotics) into metabolites that are detected in the host faeces, urine and blood. Many of these metabolites are only produced by microbes and there is accumulating evidence to suggest that these microbe-specific metabolites do act as effectors to influence human physiology. For example, the gut microbiota can digest dietary complex polysaccharides (such as fibre) into short-chain fatty acids (SCFA) such as acetate, propionate and butyrate that have a pervasive role in host physiology from nutrition to immune function. In this review we will outline our current understanding of the role of some key microbial metabolites, such as SCFA, indole and bile acids, in human health. Whilst many studies linking microbial metabolites with human health are correlative we will try to highlight examples where genetic evidence is available to support a specific role for a microbial metabolite in host health and well-being.

Advances from conventional to biochar enhanced biotreatment of dyeing wastewater: A critical review

DW (Dyeing wastewater) contains a large amount of dye organic compounds. A considerable proportion of dye itself or its intermediate products generated during wastewater treatment process exhibits CMR (Carcinogenic/Mutagenic/Toxic to Reproduction) toxicity. Compared with physicochemical methods, biological treatment is advantageous in terms of operating costs and greenhouse gas emissions, and has become the indispensable mainstream technology for DW treatment. This article reviews the adsorption and degradation mechanisms of dye organic compounds in wastewater and analyzed different biological processes, ranging from traditional methods to processes enhanced by biochar (BC). For traditional biological processes, microbial characteristics and communities were discussed, as well as the removal efficiency of different bioreactors. BC has adsorption and redox electron mediated effects, and coupling with biological treatment can further enhance the process of biosorption and degradation. Although BC coupled biological treatment shows promising dye removal, further research is still needed to optimize the treatment process, especially in terms of technical and economic competitiveness.

Decolorization, degradation and detoxification of mutagenic dye Methyl orange by novel biofilm producing plant growth-promoting rhizobacteria

Discharge of untreated dyeing wastewater nearby water-bodies is one of major causes of water pollution. Generally, bacterial strains isolated from industrial effluents and/or contaminated soils are used for the bioremediation of Methyl orange (MO), a mutagenic recalcitrant mono-azo dye, used in textiles and biomedical. However, MO degradation by biofilm producing plant growth-promoting rhizobacteria (BPPGPR) was not studied yet. In this study, 19 out of 21 BPPGPR strains decolorized 96.3-99.9% and 89.5-96.3% MO under microaerophilic and aerobic conditions, respectively from Luria-Bertani broth (LBB) followed by yeast-extract peptone and salt-optimized broth plus glycerol media within 120 h of incubation at 28 °C. Only selected BPPGPR including Pseudomonas fluorescens ESR7, P. veronii ESR13, Stenotrophomonas maltophilia ESR20, Staphylococcus saprophyticus ESD8, and P. parafulva ESB18 were examined for process optimization of MO decolorization using a single factor optimization method. This study showed that under optimal conditions (e.g., LBB, 100 mg L-1 MO, pH 7, incubation of 96 h, 28 °C), these strains could remove 99.1-99.8% and 97.6-99.5% MO under microaerophilic and aerobic conditions, respectively. Total azoreductase and laccase activities responsible for biodegradation were also remarkably activated in the biodegraded samples under optimal conditions, while these activities were repressed under unfavorable conditions (e.g., 40 °C and 7.5% NaCl). This study confirmed that MO was degraded and detoxified by these bacterial strains through breakage of azo bond. So far, this is the first report on bioremediation of MO by the BPPGPR strains. These BPPGPR strains are highly promising to be utilized for the bioremediation of dyeing wastewater in future.

The global anaerobic metabolism regulator fnr is necessary for the degradation of food dyes and drugs by Escherichia coli

IMPORTANCE

This work has broad relevance due to the ubiquity of dyes containing azo bonds in food and drugs. We report that azo dyes can be degraded by human gut bacteria through both enzymatic and nonenzymatic mechanisms, even from a single gut bacterial species. Furthermore, we revealed that environmental factors, oxygen, and L-Cysteine control the ability of E. coli to degrade azo dyes due to their impacts on bacterial transcription and metabolism. These results open up new opportunities to manipulate the azoreductase activity of the gut microbiome through the manipulation of host diet, suggest that azoreductase potential may be altered in patients suffering from gastrointestinal disease, and highlight the importance of studying bacterial enzymes for drug metabolism in their natural cellular and ecological context.

Molecular characterization of azoreductase and its potential for the decolorization of Remazol Red R and Acid Blue 29

Azoreductase is a reductive enzyme that efficiently biotransformed textile azo dyes. This study demonstrated the heterologous overexpression of the azoreductase gene in Escherichia coli for the effective degradation of Remazol Red-R and Acid-Blue 29 dyes. The AzK gene of Klebsiella pneumoniae encoding a ≈22 kDa azoreductase enzyme was cloned into the pET21+C expression vector. The inoculum size of 1.5%, IPTG concentration of 0.5 mM, and incubation time of 6 h were optimized by response surface methodology a statistical tool. The crude extract showed 76% and 74%, while the purified enzyme achieved 94% and 93% decolorization of RRR and AB-29, respectively in 0.3 h. The reaction kinetics showed that RRR had a Km and Vmax value of 0.058 mM and 1416 U mg-1, respectively at an NADH concentration of 10 mM. HPLC and GC-MS analyses showed that RRR was effectively bio-transformed by azoreductase to 2-[3-(hydroxy-amino) benzene-1-sulfonyl and AB-29 to aniline and 3-nitrosoaniline. This study explored the potential of recombinant azoreductase isolated from K. pneumoniae in the degradation of toxic textile azo dyes into less toxic metabolites.

Influence of Different Diets on the Degradation of Sulfasalazine by Colon Bacteria Determined Using MimiCol3

The microbiome of the colon is characterized by its great diversity. This varies not only intra- but also interindividually and is influenced by endogenous and exogenous factors, such as dietary and lifestyle factors. The aim of this work was to investigate the extent to which the degradation of the drug sulfasalazine is influenced by different microbiota. Therefore, the in vitro model MimiCol3 was used, which represents the physiological conditions of the ascending colon. In addition to a representative physiological volume, the pH value, redox potential and an anaerobic atmosphere are important to provide the bacteria with the best possible growth conditions. Stool samples were taken from three healthy subjects, comparing omnivorous, vegetarian and meat-rich diets, and cultured for 24 h. However, the nutrient medium used for cultivation led to the alignment of the bacterial composition of the microbiota. The previously observed differences between the diets could not be maintained. Nevertheless, the similar degradation of sulfasalazine was observed in all microbiota studied in MimiCol3. This makes MimiCol3 a suitable in vitro model for metabolism studies in the gut microbiome.

Toxic effects of Arianor Ebony hair dye on human cells

To evaluate the risks of hair dye exposure, we investigated cellular and molecular effects of Arianor Ebony dye, which is a mixture of azo and anthraquinone dyes, used in the composition of the black color. Cytotoxicity, genotoxicity, and gene expression of relevant molecules of apoptotic and oxidative stress mechanisms were investigated in HepG2 cells exposed to Arianor Ebony. Results showed that the dye did not induce cytotoxicity to exposed cells at a concentration up to 50 µg/mL compared to the negative control. However, genotoxic assays indicated that the dye was able to damage the genetic material at a concentration of 25 µg/mL, with induction factor values of exposed cells two- to five-fold higher than those recorded for the negative control. Moreover, the lowest observed effect concentration was 12.5 µg/mL. For gene expression, relevant changes were observed in cytochrome c and caspase 9, which decreased in cells incubated with the dye in a dose-dependent manner when compared with the negative control. In parallel, the expression of genes for antioxidant enzymes was increased in exposed cells, suggesting the presence of metabolic routes that protect cells against the toxic effect of the dye, avoiding exacerbated cellular death. Results suggested that the dye disrupted cellular homeostasis through mitochondrial dysfunction, which may be hazardous to human health. Thus, further investigations are necessary to deeply understand the mechanisms of action of the dye, considering its toxic potential found in our ex vivo assays.

Bactericidal and biocatalytic temperature responsive microgel based self-cleaning membranes for water purification

The present study focuses on creating an antimicrobial and biocatalytic smart gating membrane by synthesizing unique core-shell microgels. The core-shell microgels are synthesized by grafting short chains of poly(ethylenimine) (PEI) onto a poly((N-isopropyl acrylamide)-co-glycidyl methacrylate)) (P(NIPAm-co-GMA)) core. Subsequently, the produced microgels are utilized as a substrate for synthesizing and stabilizing silver nanoparticles (Ag NPs) through an in-situ approach. These Ag NPs immobilized microgels are then suction filtered over a polyethylene terephthalate (PET) track-etched support to create cross-linked composite microgel membranes (CMMs). After structural and permeation characterization of the prepared CMMs, the laccase enzyme is then covalently grafted to the surface of the membrane and tested for its effectiveness in degrading Reactive red-120 dye. The laccase immobilized biocatalytic CMMs show effective degradation of the Reactive red-120 by 71%, 48%, and 34% at pH 3, 4, and 5, respectively. Furthermore, the immobilized laccase enzyme showed better activity and stability in terms of thermal, pH, and storage compared to the free laccase, leading to increased reusability. The unique combination of Ag NPs and laccase on a thermoresponsive microgel support resulted in a responsive self-cleaning membrane with excellent antimicrobial and dye degradation capabilities for environmentally friendly separation technology.

Heterogeneous biocatalytic system for effective decolorization of textile dye effluent

The current physicochemical methods for decolorizing toxic synthetic dyes are not sustainable to halt the environmental damage as they are expensive and often produce concentrated sludge, which may lead to secondary disposal problems. Biocatalysis (microbes and/or their enzymes) is a cost-effective, versatile, energy-saving and clean alternative. The most common enzymes involved in dye degradation are laccases, azoreductases and peroxidases. Toxic dyes could be converted into less harmful byproducts through the combined action of many enzymes or the utilization of whole cells. The action of whole cells to treat dye effluents is either by biosorption or degradation (aerobic or anaerobic). Using immobilized cells or enzymes will offer advantages such as superior stability, persistence against harsh environmental conditions, reusability and longer half-lives. This review envisages the recent strategies of immobilization and bioreactor considerations with the immobilized system as the effective treatment of textile dye effluents. Packed bed reactors are the most popular heterogeneous biocatalytic reactors for dye decolorization due to their efficiency and cost-effectiveness.

Investigating Bio-Inspired Degradation of Toxic Dyes Using Potential Multi-Enzyme Producing Extremophiles

Biological treatment methods overcome many of the drawbacks of physicochemical strategies and play a significant role in removing dye contamination for environmental sustainability. Numerous microorganisms have been investigated as promising dye-degrading candidates because of their high metabolic potential. However, few can be applied on a large scale because of the extremely harsh conditions in effluents polluted with multiple dyes, such as alkaline pH, high salinity/heavy metals/dye concentration, high temperature, and oxidative stress. Therefore, extremophilic microorganisms offer enormous opportunities for practical biodegradation processes as they are naturally adapted to multi-stress conditions due to the special structure of their cell wall, capsule, S-layer proteins, extracellular polymer substances (EPS), and siderophores structural and functional properties such as poly-enzymes produced. This review provides scientific information for a broader understanding of general dyes, their toxicity, and their harmful effects. The advantages and disadvantages of physicochemical methods are also highlighted and compared to those of microbial strategies. New techniques and methodologies used in recent studies are briefly summarized and discussed. In particular, this study addresses the key adaptation mechanisms, whole-cell, enzymatic degradation, and non-enzymatic pathways in aerobic, anaerobic, and combination conditions of extremophiles in dye degradation and decolorization. Furthermore, they have special metabolic pathways and protein frameworks that contribute significantly to the complete mineralization and decolorization of the dye when all functions are turned on. The high potential efficiency of microbial degradation by unculturable and multi-enzyme-producing extremophiles remains a question that needs to be answered in practical research.

Construction of bacterial consortium for efficient degradation of mixed pharmaceutical dyes

Synthetic dyes are established colorants in the pharmaceutical industries for the coating and coloration of tablets, capsules, etc. to mark the specific formulation and dosage, improve the stability, and esthetic value. The pharmaceuticals manufacturing process releases large volumes of dye-containing wastewaters, contributing to eco-toxic concerns related to different health risks. In this study, biodegradation of amaranth, sunset yellow, tartrazine, indigo carmine, and quinoline yellow dyes was investigated in the mixed environment. Initially, 24 tolerant bacterial strains were isolated from pharmaceutical wastewater samples, among which 19 strains were found to be non-virulent. Five different consortia were constructed by considering the 19 strains among which C1 consisting of strains DY7, 10, 11, and 18 was found to be the most potential consortium with an overall efficiency of 96.65% dye degradation in the presence of glucose after 15 days. The strains DY7, 10, 11, and 18 were identified as members of the Klebsiella genus by 16S rRNA partial sequencing. The cell wall structure, carbohydrate utilization profile, and metabolic characterization were conducted on the selected strains of C1. Among the 25 different antibiotics, DY7 and DY11 exhibited the highest zone of growth inhibition in the presence of cefixime, and DY10 was restricted by chloramphenicol whereas DY18 was found sensitive to ceftazidime/tazobactam.

The Impact of Food Additives on the Abundance and Composition of Gut Microbiota

The gut microbiota has been confirmed as an important part in human health, and is even take as an 'organ'. The interaction between the gut microbiota and host intestinal environment plays a key role in digestion, metabolism, immunity, inflammation, and diseases. The dietary component is a major factor that affects the composition and function of gut microbiota. Food additives have been widely used to improve the color, taste, aroma, texture, and nutritional quality of processed food. The increasing variety and quantity of processed food in diets lead to increased frequency and dose of food additives exposure, especially artificial food additives, which has become a concern of consumers. There are studies focusing on the impact of food additives on the gut microbiota, as long-term exposure to food additives could induce changes in the microbes, and the gut microbiota is related to human health and disease. Therefore, the aim of this review is to summarize the interaction between the gut microbiota and food additives.

Diverse but desolate landscape of gut microbial azoreductases: A rationale for idiopathic IBD drug response

Prodrugs reliant on microbial activation are widely used but exhibit a range of efficacies that remain poorly understood. The anti-inflammatory compound 5-aminosalicylic acid (5-ASA), which is packaged in a variety of azo-linked prodrugs provided to most Ulcerative Colitis (UC) patients, shows confounding inter-individual variabilities in response. Such prodrugs must be activated by azo-bond reduction to form 5-ASA, a process that has been attributed to both enzymatic and non-enzymatic catalysis. Gut microbial azoreductases (AzoRs) are the first catalysts shown to activate azo-linked drugs and to metabolize toxic azo-chemicals. Here, we chart the scope of the structural and functional diversity of AzoRs in health and in patients with the inflammatory bowel diseases (IBDs) UC and Crohn's Disease (CD). Using structural metagenomics, we define the landscape of gut microbial AzoRs in 413 healthy donor and 1059 IBD patient fecal samples. Firmicutes encode a significantly higher number of unique AzoRs compared to other phyla. However, structural and biochemical analyses of distinct AzoRs from the human microbiome reveal significant differences between prevalent orthologs in the processing of toxic azo-dyes, and their generally poor activation of IBD prodrugs. Furthermore, while individuals with IBD show higher abundances of AzoR-encoding gut microbial taxa than healthy controls, the overall abundance of AzoR-encoding microbes is markedly low in both disease and health. Together, these results establish that gut microbial AzoRs are functionally diverse but sparse in both health and disease, factors that may contribute to non-optimal processing of azo-linked prodrugs and idiopathic IBD drug responses.

Multi-omic analysis of host-microbial interactions central to the gut-brain axis

The gut microbiota impact numerous aspects of human physiology, including the central nervous system (CNS). Emerging work is now focusing on the microbial factors underlying the bi-directional communication network linking host and microbial systems within the gastrointestinal tract to the CNS, the "gut-brain axis". Neurotransmitters are key coordinators of this network, and their dysregulation has been linked to numerous neurological disease states. As the bioavailability of neurotransmitters is modified by gut microbes, it is critical to unravel the influence of the microbiota on neurotransmitters in the context of the gut-brain axis. Here we review foundational studies that defined molecular relationships between the microbiota, neurotransmitters, and the gut-brain axis. We examine links between the gut microbiome, behavior, and neurological diseases, as well as microbial influences on neurotransmitter bioavailability and physiology. Finally, we review multi-omics technologies uniquely applicable to this area, including high-throughput genetics, modern metabolomics, structure-guided metagenomics, targeted proteomics, and chemogenetics. Interdisciplinary studies will continue to drive the discovery of molecular mechanisms linking the gut microbiota to clinical manifestations of neurobiology.

Biofilm-mediated decolorization, degradation and detoxification of synthetic effluent by novel biofilm-producing bacteria isolated from textile dyeing effluent

Biofilm-mediated bioremediation of xenobiotic pollutants is an environmental friendly biological technique. In this study, 36 out of 55 bacterial isolates developed biofilms in glass test tubes containing salt-optimized broth plus 2% glycerol (SOBG). Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and Congo red- and Calcofluor binding results showed biofilm matrices contain proteins, curli, nanocellulose-rich polysaccharides, nucleic acids, lipids, and peptidoglycans. Several functional groups including -OH, N-H, C-H, CO, COO^-, -NH_2, PO, C-O, and C-C were also predicted. By sequencing, ten novel biofilm-producing bacteria (BPB) were identified, including Exiguobacterium indicum ES31G, Kurthia gibsonii ES43G, Kluyvera cryocrescens ES45G, Cedecea lapagei ES48G, Enterobacter wuhouensis ES49G, Aeromonas caviae ES50G, Lysinibacillus sphaericus ES51G, Acinetobacter haemolyticus ES52G, Enterobacter soli ES53G, and Comamonas aquatica ES54G. The Direct Red (DR) 28 (a carcinogenic and mutagenic dye used in dyeing and biomedical processes) decolorization process was optimized in selected bacterial isolates. Under optimum conditions (SOBG medium, 75 mg L^-1 dye, pH 7, 28 °C, microaerophilic condition and within 72 h of incubation), five of the bacteria tested could decolorize 97.8% ± 0.56-99.7% ± 0.45 of DR 28 dye. Azoreductase and laccase enzymes responsible for biodegradation were produced under the optimum condition. UV-Vis spectral analysis revealed that the azo (-NN-) bond peak at 476 nm had almost disappeared in all of the decolorized samples. FTIR data revealed that the foremost characteristic peaks had either partly or entirely vanished or were malformed or stretched. The chemical oxygen demand decreased by 83.3-91.3% in the decolorized samples, while plant probiotic bacterial growth was indistinguishable in the biodegraded metabolites and the original dye. Furthermore, seed germination (%) was higher in the biodegraded metabolites than the parent dye. Thus, examined BPB could provide potential solutions for the bioremediation of industrial dyes in wastewater.

Biodegradation of Congo Red Using Co-Culture Anode Inoculum in a Microbial Fuel Cell

Congo red is an azo dye widely used as a colouring agent in textile industries. It is a serious threat due to its carcinogenic effects. Its degradation has been challenging due to its complex yet stable structure. The present study was aimed to investigate the effective degradation of Congo red by bioremediating bacteria isolated from different environments. To investigate predominant microorganisms that degrade Congo red and its functions in microbial fuel cells (MFCs), strains isolated from cow dung (Enterococcus faecalis SUCR1) and soil (Pseudomonas aeruginosa PA1_NCHU) were used as a co-culture inocula. The remarkable results establish that E. faecalis as an excellent microbial source for the biological degradation of dye-contaminated wastewater treatment alongside bioactive treating wastewater with varied concentrations of congo red dye. The highest efficiency percentage of dye degradation was 98% after 3 days of incubation at pH 7 and 37 °C, whereas findings have shown that the decolorization at pH 5 and 6 was lower at 66% and 83.3%, respectively, under the same incubation conditions. Furthermore, the co-culture of E. faecalis SUCR1 and P. aeruginosa at a 1:1 ratio demonstrated improved power generation in MFCs. The maximum power density of 7.4 W/m3 was recorded at a 150 mg L−1 concentration of Congo red, indicating that the symbiotic relation between these bacterium resulted in improved MFCs performance simultaneous to dye degradation.

Iron-dependent mutualism between Chlorella sorokiniana and Ralstonia pickettii forms the basis for a sustainable bioremediation system

Phototrophic communities of autotrophic microalgae and heterotrophic bacteria perform complex tasks of nutrient acquisition and tackling environmental stress but remain underexplored as a basis for the bioremediation of emerging pollutants. In industrial monoculture designs, poor iron uptake by microalgae limits their productivity and biotechnological efficacy. Iron supplementation is expensive and ineffective because iron remains insoluble in an aqueous medium and is biologically unavailable. However, microalgae develop complex interkingdom associations with siderophore-producing bacteria that help solubilize iron and increase its bioavailability. Using dye degradation as a model, we combined environmental isolations and synthetic ecology as a workflow to design a simplified microbial community based on iron and carbon exchange. We established a mutualism between the previously non-associated alga Chlorella sorokiniana and siderophore-producing bacterium Ralstonia pickettii. Siderophore-mediated increase in iron bioavailability alleviated Fe stress for algae and increased the reductive iron uptake mechanism and bioremediation potential. In exchange, C. sorokiniana produced galactose, glucose, and mannose as major extracellular monosaccharides, supporting bacterial growth. We propose that extracellular iron reduction by ferrireductase is crucial for azoreductase-mediated dye degradation in microalgae. These results demonstrate that iron bioavailability, often overlooked in cultivation, governs microalgal growth, enzymatic processes, and bioremediation potential. Our results suggest that phototrophic communities with an active association for iron and carbon exchange have the potential to overcome challenges associated with micronutrient availability, while scaling up bioremediation designs.

Biodegradation of Reactive Yellow-145 azo dye using bacterial consortium: A deterministic analysis based on degradable Metabolite, phytotoxicity and genotoxicity study

Azo dyes are used at larger-scale as coloring agent in the textile industry. It generates a huge amount of dye containing wastewater and its toxicity threatens all kinds of life and also impacts human beings. At present, more impetus is being given to the biological treatment of dye effluent because of its azoreductase enzyme action to break down azo bond which leads to decolorization and degradation of dye. Bacterial consortium of E. asburiae and E. cloacae (1:1 ratio) was used for degradation and decolorization of Reactive Yellow-145 (RY-145) dye. The optimization of dye concentration, temperature, pH, and media has been carried out to determine the conditions required for maximum degradation and decolorization. The mixed consortium (10%) has shown 98.78% decolorization of RY-145 dye under static condition at 500 mgL^-1 concentration, 35 °C and pH 7.0 at 12 h contact period. FTIR analysis showed formation of new functional groups in the treated dye, such as O-H stretch at 1361 cm^-1, C-H stretch at 890 cm^-1, N-H stretch at 1598 cm^-1 and aromatic C-H at 671 cm^-1 revealing degradation of dye. Biodegraded metabolites of RY-145 dye were identified through GC-MS analysis that includes 2-Cyclohexen-1-ol, 5-Nitroso-2, 4, 6-triaminopyrimidine, Octahydroquinoline-9-hydroxyperoxide, Tetramethyl-2-hexadecen-1-ol, 9-Octadecanoic acid, methyl ester and Hexadecanoic acid, methyl ester, respectively which have industrial applications. Cyclohexane was used in gasoline and adhesive while Octahydroquinoline-9-hydroxyperoxide and 5-Nitroso-2, 4, 6-triaminopyrimidine were used in manufacturing drugs. Tetramethyl-2-hexadecen-1-ol, 9-Octadecanoic acid, methyl ester and Hexadecanoic acid, methyl ester are antimicrobial and antioxidant. Phytotoxicity test also showed non-toxic effects of treated dye on germination of Cicer arietinum and Vigna radiata seeds. Similarly, genotoxicity study indicated less toxic effects of biodegraded dye products on Mitotic index (MI) and cell division of Allium cepa.

Efficient removal of azo dyes by Enterococcus faecalis R1107 and its application in simulated textile effluent treatment

This study aimed to exploit the potential of Enterococcus faecalis R1107 in the bioremediation of azo dyes. The maximal decolorization of Congo Red (CR), Reactive Black 5 (RB5), and Direct Black 38 (DB38) were 90.17%, 96.82%, and 81.95%, respectively, with the bacterial treatment for 48 h. 65.57% of CR and 72.64% of RB5 could be decolorized by E. faecalis R1107 within 48 h when the concentration of azo dyes increased up to 1000 mg/L. FTIR analysis confirmed that E. faecalis R1107 could effectively break down the chemical structures of three azo dyes. E. faecalis R1107 alleviated the phytotoxicity of azo dyes and improved seed germination, which contributed to the increase in the lengths of roots, stems, and leaves of Vigna radiata seedlings. Transcriptomic analysis suggested that the gene regulatory networks in E. faecalis R1107 synergistically improved the degradation and detoxification of RB5, including the major metabolic pathways, the secondary metabolism, the transport system, the amino acid metabolic pathways, and the signal transduction systems. Simulated textile effluent (STE) was used to mimic real textile effluent to evaluate the bioremediation potential of E. faecalis R1107, and 72.79% STE can be decolorized after E. faecalis R1107 treatment for 48 h. In summary, our study demonstrated that E. faecalis R1107 might be well suitable for potential applications in the bioremediation of textile effluent.

Biodegradation and Detoxification of Azo Dyes by Halophilic/Halotolerant Microflora Isolated From the Salt Fields of Tibet Autonomous Region China

This study aimed to decolorize azo dyes in high-salt industrial wastewater under high-salt and low oxygen conditions using extreme halophilic/halotolerant bacteria screened from the salt fields of Tibet, which consisted of Enterococcus, unclassified Enterobacteriaceae, Staphylococcus, Bacillus, and Kosakonia. Under the optimal conditions, 600 mg/l Congo red, Direct Black G (DBG), Amaranth, methyl red, and methyl orange could be completely decolorized in 24, 8, 8, 12, and 12 h, respectively. When the DBG concentration was 600 mg/l, NADH–DCIP, laccase, and azo reductase were confirmed to be the primary reductase and oxidase during the degradation process, and the degradation pathways were verified. The microflora could not only tolerate changes in salt concentrations of 0–80 g/l, but also displayed strong degradative ability. Under high-salt concentrations (≥ 60 g/l NaCl), NADH–DCIP reductase was primarily used to decolorize the azo dye. However, under low salt concentrations (≤ 40 g/l NaCl), azo reductase began to function, and manganese peroxidase and lignin peroxidase could cooperate to participate in DBG degradation. Additionally, the halophilic/halophilic microflora was shown to convert the toxic DBG dye to metabolites of low toxicity based on phytotoxicity analysis, and a new mechanism for the microflora to degrade DBG was proposed based on intermediates identified by liquid chromatography-mass spectrometry (LC–MS). This study revealed that the halophilic/halophilic microflora has effective ecological and industrial value for treating wastewater from the textile industry.

Pharmacomicrobiomics: Influence of gut microbiota on drug and xenobiotic metabolism

Gut microbiota is the most diverse and complex biological ecosystem, which is estimated to consist of greater than 5 million distinct genes and 100 trillion cells which are in constant communication with the host environment. The interaction between the gut microbiota and drugs and other xenobiotic compounds is bidirectional, quite complicated, and not fully understood yet. The impact of xenobiotics from pollution, manufacturing processes or from the environment is harmful to human health at varying degrees and this needs to be recognized and addressed. The gut microbiota is capable of biotransforming/metabolizing of various drugs and xenobiotic compounds as well as altering the activity and toxicity of these substances, thereby influencing how a host responds to drugs and xenobiotics and this emerging field is known as pharmacomicrobiomics. In this review, we discussed different mechanisms of drug-gut microbiota interaction and highlighted the influence of drug-gut microbiome interactions on the clinical response in humans.

Biodegradation, Decolorization, and Detoxification of Di-Azo Dye Direct Red 81 by Halotolerant, Alkali-Thermo-Tolerant Bacterial Mixed Cultures

Azo dyes impact the environment and deserve attention due to their widespread use in textile and tanning industries and challenging degradation. The high temperature, pH, and salinity used in these industries render industrial effluent decolorization and detoxification a challenging process. An enrichment technique was employed to screen for cost-effective biodegraders of Direct Red 81 (DR81) as a model for diazo dye recalcitrant to degradation. Our results showed that three mixed bacterial cultures achieved ≥80% decolorization within 8 h of 40 mg/L dye in a minimal salt medium with 0.1% yeast extract (MSM-Y) and real wastewater. Moreover, these mixed cultures showed ≥70% decolorization within 24 h when challenged with dye up to 600 mg/L in real wastewater and tolerated temperatures up to 60 °C, pH 10, and 5% salinity in MSM-Y. Azoreductase was the main contributor to DR81 decolorization based on crude oxidative and reductive enzymatic activity of cell-free supernatants and was stable at a wide range of pH and temperatures. Molecular identification of azoreductase genes suggested multiple AzoR genes per mixed culture with a possible novel azoreductase gene. Metabolite analysis using hyphenated techniques suggested two reductive pathways for DR81 biodegradation involving symmetric and asymmetric azo-bond cleavage. The DR81 metabolites were non-toxic to Artemia salina nauplii and Lepidium sativum seeds. This study provided evidence for DR81 degradation using robust stress-tolerant mixed cultures with potential use in azo dye wastewater treatment.

Naphthalimide-Based Azo-Functionalized Supramolecular Vesicle in Hypoxia-Responsive Drug Delivery

Supramolecular materials that respond to external triggers are being extensively utilized in developing spatiotemporal control in biomedical applications ranging from drug delivery to diagnostics. The present article describes the development of self-assembled vesicles in 1:9 (v/v), tetrahydrofuran (THF)-water by naphthalimide-based azo moiety containing amphiphile (NI-Azo) where azo moiety would act as the stimuli-responsive junction. The self-assembly of NI-Azo took place through H-type of aggregation. Microscopic and spectroscopic analyses confirmed the formation of supramolecular vesicles with a dimension of 200-250 nm. Azo (-N═N-) moiety is known to get reduced to amine derivatives in the presence of the azoreductase enzyme, which is overexpressed in the hypoxic microenvironment. The absorbance intensity of this characteristic azo (-N═N-) moiety of NI-Azo (1:9 (v/v), THF-water) at 458 nm got diminished in the presence of both extracellular and intracellular bacterial azoreductase extracted from Escherichia coli bacteria. The same observation was noted in the presence of sodium dithionite (mimic of azoreductase), indicating that azoreductase/sodium dithionite induced azo bond cleavage of NI-Azo, which was confirmed by matrix-assisted laser desorption ionization time-of-flight spectrometric data of the corresponding aromatic amine fragments. The anticancer drug, curcumin, was encapsulated inside NI-Azo vesicles that successfully killed B16F10 cells (cancer cells) in CoCl₂-induced hypoxic environment owing to the azoreductase-responsive release of drug. The cancer cell killing efficiency by curcumin-loaded NI-Azo vesicles in the hypoxic condition was 2.15-fold higher than that of the normoxic environment and 2.4-fold higher compared to that of native curcumin in the hypoxic condition. Notably, cancer cell killing efficiency of curcumin-loaded NI-Azo vesicles was 4.5- and 1.9-fold higher than that of noncancerous NIH3T3 cells in normoxic and hypoxic environments, respectively. Cell killing was found to be primarily through the early apoptotic pathway.

Enzymatic biodegradation, kinetic study, and detoxification of Reactive Red-195 by Halomonas meridiana isolated from Marine Sediments of Andaman Sea, India

Azo dyes are a significant class of hazardous chemicals that are extensively utilised in diverse industries. Industries that manufacture and consume reactive azo dyes generate hyper-saline wastewater. The ability of halotolerant bacteria to thrive under extreme environmental conditions thus makes them a potential candidate for reactive azo dye degradation. An efficient halotolerant bacterium (isolate SAIBP-6) with the capability to degrade 87.15% of azo dye Reactive Red 195 (RR-195) was isolated from sea sediment and identified as Halomonas meridiana SAIBP-6. Strain SAIBP-6 maintained potential decolourisation under a wide range of environmental conditions viz. 35-45°C temperature, 50-450 mg/L RR-195, pH 7-9, and 50-150 g/L NaCl. However, maximum decolourisation occurred at 40°C, 200 mg/L RR-195 dye, pH 9, and 50 g/L NaCl, under static conditions. Tyrosinase and azoreductase were responsible for dye degradation. The reaction catalysed by these enzymes followed zero-order kinetics. The maximum velocity (Vmax) of the enzymatic reaction was 4.221 mg/(L.h) and the Michaelis constant (Km) was 517.982 mg/L. Strain SAIBP-6 also efficiently decolourised Reactive Black-5 and Reactive Yellow-160 dye. The biodegradation process was further studied with the help of UV-Vis spectral scan, ultra-high performance liquid chromatography (UPLC), fourier-transform infra-red spectroscopy (FT-IR), and proton nuclear magnetic resonance (¹H NMR) analysis. Finally, cytogenotoxicity assay conducted with the meristematic root tip cells of Allium cepa and phytotoxicity assay conducted with the seeds of Vigna mungo led to the inference that strain SAIBP-6 significantly reduced the toxicity of RR-195 after biodegradation.

Microbial approaches for sustainable remediation of dye-contaminated wastewater: a review

The coloured effluents produced from different industries, such as textile, plastics, printing, cosmetics, leather and paper, are extremely toxic and a tremendous threat to the aquatic organisms and human beings. The removal of coloured dye pollutants from the aqueous environment is a great challenge and a pressing task. The growing demand for low-cost and efficient treatment approaches has given rise to alternative and eco-friendly methods, such as biodegradation and microbial remediation. This work summarizes the overview and current research on the remediation of dye pollutants from the aqueous environment by microbial bio-sorbents, such as bacteria, fungi, algae, and yeast. In addition, dye degradation capabilities of microbial enzymes have been highlighted and discussed. Further, the influence of various experimental parameters, such as temperature, pH, and concentrations of nutrients, and dye, has been summarized. The proposed mechanism for dye removal by microorganisms is also discussed. The object of this review is to provide a state-of-the-art of microbial remediation technologies in eliminating dye pollutants from water resources.

Decolorization of reactive blue 13 by Sporotrichum sp. and cytotoxicity of biotreated dye solution

Wastewater from the textile industry contaminated with azo dyes affects the environment negatively, causes pollution, and threatens environmental balance. Among various methods for wastewater treatment, bioremediation emerges as an environmentally friendly, economical, and sustainable solution. In this study, white-rot fungus Sporotrichum sp. was employed to decolorize reactive blue 13 (RB13). The long-term decolorization capacity of the fungus was investigated by a sequential batch experiment under optimized conditions. The fungus showed high decolorization efficiency upon repeating usage, and its decolorization efficiency decreased from 97.4% to 87.09% after transferring to a freshly prepared medium seven times. The MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay) method using Chinese Hamster Lung V79 379A was performed to assess the cytotoxicity of treated water samples. This study revealed that Sporotrichum sp. has short-term enzymatic and long-term biosorption capacity on reactive blue 13 and the decolorization potential of the alive and dead cells is impressively high. PRACTITIONER POINTS: White-rot fungus Sporotrichum sp. is able to decolorize sulfonated azo-dye reactive blue 13 upon sequential incubation in freshly prepared dye solution. The decolorization mechanism of the fungus is estimated to be bioadsorption. Sporotrichum sp. can be considered for long-term usage and immobilization applications.

An Integrative Approach to Study Bacterial Enzymatic Degradation of Toxic Dyes

Synthetic dyes pose a large threat to the environment and consequently to human health. Various dyes are used in textile, cosmetics, and pharmaceutical industries, and are released into the environment without any treatment, thus adversely affecting both the environment and neighboring human populations. Several existing physical and chemical methods for dye degradation are effective but have many drawbacks. Biological methods over the years have gained importance in the decolorization and degradation of dye and have also overcome the disadvantages of physiochemical methods. Furthermore, biological methods are eco-friendly and lead to complete decolorization. The mechanism of decolorization and degradation by several bacterial enzymes are discussed in detail. For the identification of ecologically sustainable strains and their application at the field level, we have focused on bioaugmentation aspects. Furthermore, in silico studies such as molecular docking of bacterial enzymes with dyes can give a new insight into biological studies and provide an easy way to understand the interaction at the molecular level. This review mainly focuses on an integrative approach and its importance for the effective treatment and decolorization of dyes.

Biochemical characterization of a novel azo reductase named BVU5 from the bacterial flora DDMZ1: application for decolorization of azo dyes

One of the main mechanisms of bacterial decolorization and degradation of azo dyes is the use of biological enzymes to catalyze the breaking of azo bonds. This paper shows the expression and properties of a novel azo reductase (hybrid-cluster NAD(P)-dependent oxidoreductase, accession no. A0A1S1BVU5, named BVU5) from the bacterial flora DDMZ1 for degradation of azo dyes. The molecular weight of BVU5 is about 40.1 kDa, and it contains the prosthetic group flavin mononucleotide (FMN). It has the decolorization ability of 80.1 ± 2.5% within 3 min for a dye concentration of 20 mg L⁻¹, and 53.5 ± 1.8% even for a dye concentration of 200 mg L⁻¹ after 30 min. The optimum temperature of enzyme BVU5 is 30 °C and the optimum pH is 6. It is insensitive to salt concentration up to a salinity level of 10%. Furthermore, enzyme BVU5 has good tolerance toward some metal ions (2 mM) such as Mn²⁺, Ca²⁺, Mg²⁺ and Cu²⁺ and some organic solvents (20%) such as DMSO, methanol, isopentyl, ethylene glycol and N-hexane. However, the enzyme BVU5 has a low tolerance to high concentrations of denaturants. In particular, it is sensitive to the denaturants guanidine hydrochloride (GdmCl) (2 M) and urea (2 M). Analysis of the dye substrate specificity shows that enzyme BVU5 decolorizes most azo dyes, which is indicating that the enzyme is not strictly substrate specific, it is a functional enzyme for breaking the azo structure. Liquid chromatography/time-of-flight/mass spectrometry (LC-TOF-MS) revealed after the action of enzyme BVU5 that some intermediate products with relatively large molecular weights were produced; this illustrates a symmetric or an asymmetric rapid cleavage of the azo bonds by this enzyme. The potential degradation pathways and the enzyme-catalyzed degradation mechanism are deduced in the end of this paper. The results give insight into the potential of a rapid bio-pretreatment by enzyme BVU5 for processing azo dye wastewater.

The combination of BVU5 enzyme and coenzyme NADH can quickly degrade the azo dye RB5.

Structural diversity, functional aspects and future therapeutic applications of human gut microbiome

The research on human gut microbiome, regarded as the black box of the human body, is still at the stage of infancy as the functional properties of the complex gut microbiome have not yet been understood. Ongoing metagenomic studies have deciphered that the predominant microbial communities belong to eubacterial phyla Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, Cyanobacteria, Verrucomicrobia and archaebacterial phylum Euryarchaeota. The indigenous commensal microbial flora prevents opportunistic pathogenic infection and play undeniable roles in digestion, metabolite and signaling molecule production and controlling host's cellular health, immunity and neuropsychiatric behavior. Besides maintaining intestinal health via short-chain fatty acid (SCFA) production, gut microbes also aid in neuro-immuno-endocrine modulatory molecule production, immune cell differentiation and glucose and lipid metabolism. Interdependence of diet and intestinal microbial diversity suggests the effectiveness of pre- and pro-biotics in maintenance of gut and systemic health. Several companies worldwide have started potentially exploiting the microbial contribution to human health and have translated their use in disease management and therapeutic applications. The present review discusses the vast diversity of microorganisms playing intricate roles in human metabolism. The contribution of the intestinal microbiota to regulate systemic activities including gut-brain-immunity crosstalk has been focused. To the best of our knowledge, this review is the first of its kind to collate and discuss the companies worldwide translating the multi-therapeutic potential of human intestinal microbiota, based on the multi-omics studies, i.e. metagenomics and metabolomics, as ready solutions for several metabolic and systemic disorders.

Compositional variation of the human fecal microbiome in relation to azo-reducing activity: a pilot study

Background

Through an arsenal of microbial enzymes, the gut microbiota considerably contributes to human metabolic processes, affecting nutrients, drugs, and environmental poisons. Azoreductases are a predominant group of microbiota-derived enzymes involved in xenobiotic metabolism and drug activation, but little is known about how compositional changes in the gut microbiota correlate with its azo-reducing activity.

Results

To this end, we used high-throughput 16S rRNA amplicon sequencing, with Illumina MiSeq, to determine the microbial community composition of stool samples from 16 adults with different azo-reducing activity. High azo-reducing activity positively correlated with the relative abundance of phylum Firmicutes (especially genera Streptococcus and Coprococcus) but negatively with phylum Bacteroidetes (especially genus Bacteroides). Typical variations in the Firmicutes-to-Bacteroidetes and Prevotella-to-Bacteroides ratios were observed among samples. Multivariate analysis of the relative abundance of key microbial taxa and other diversity parameters confirmed the Firmicutes proportion as a major variable differentiating high and non-azo-reducers, while Bacteroidetes relative abundance was correlated with azo-reduction, sex, and BMI.

Conclusions

This pilot study showed that stool samples with higher azo-reducing activity were enriched in Firmicutes but with relatively fewer Bacteroidetes. More samples and studies from different geographical areas are needed to bolster this conclusion. Better characterization of different azoreductase-producing gut microbes will increase our knowledge about the fate and differential human responses to azodye-containing drugs or orally consumed chemicals, thus contributing to efforts towards implementing microbiome testing in precision medicine and toxicology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00454-0.

The decolorization and degradation of azo dyes by two Stenotrophomonas strains isolated from textile effluent (Tepetitla, Mexico)

Stenotrophomonas' metabolic versatility plays important roles in the remediation of contaminated environment and plant growth promotion. We investigated two Stenotrophomonas strains isolated from textile polluted sewage for their ability to decolorize and degrade azo dyes. Two Stenotrophomonas strains (TepeL and TepeS) were isolated from textile effluents (Tepetitla, Mexico) using the selective agar Stenotrophomonas vancomycin, imipenem, amphotericin B agar (SVIA). Isolates' identity was determined by the sequencing of their partial 16S rRNA fragments. Their abilities to decolorize dyes were tested in a Luria broth supplemented with varying concentrations (50 mg/L-1 g/L) of textile dyes (acidic red, methyl orange, reactive green, acidic yellow, and reactive black). Fourier-transform infrared (FTIR) spectroscopy and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) metabolite analyses were used to determine the effect of the isolates' growth on the dyes (acidic red, methyl orange). We also identified the enzymes that may be involved in the degradation process. Phylogenetic analysis based on the 16S rDNA sequences showed that the isolates belong to the genus Stenotrophomonas. Stenotrophomonas sp. TepeL and TepeS respectively decolorize all the azo dyes at the tested concentration except at 1 g/L and degraded the azo dyes. The degradation resulted in the formation of N, N-dimethyl p-phenylenediamine, and sodium 4-amino-1-naphthalenesulfonate from methyl orange and acid red. TepeL and TepeS rapidly decolorized and degraded the azo dyes tested. This result showed that the two isolates have a good potential for the decontamination of textile effluents.

Environmental Influences on the Human Microbiome and Implications for Noncommunicable Disease

The human microbiome contributes metabolic functions, protects against pathogens, educates the immune system, and through these basic functions, directly or indirectly, affects most of our physiologic functions. Here, we consider the human microbiome and its relationship to several major noncommunicable human conditions, including orodigestive tract cancers, neurologic diseases, diabetes, and obesity. We also highlight the scope of contextual macroenvironmental factors (toxicological and chemical environment, built environment, and socioeconomic environment) and individual microenvironmental factors (smoking, alcohol, and diet) that may push the microbiota toward less healthy or more healthy conditions, influencing the development of these diseases. Last, we highlight current uncertainties and challenges in the study of environmental influences on the human microbiome and implications for understanding noncommunicable disease, suggesting a research agenda to strengthen the scientific evidence base.

Trends in small organic fluorescent scaffolds for detection of oxidoreductase

Oxidoreductases are diverse class of enzymes engaged in modulating the redox homeostasis and cellular signaling cascades. Abnormal expression of oxidoreductases including thioredoxin reductase, azoreductase, cytochrome oxidoreductase, tyrosinase and monoamine oxidase leads to the initiation of numerous disorders. Thus, enzymes are the promising biomarkers of the diseased cells and their accurate detection has utmost significance for clinical diagnosis. The detection method must be extremely selective, sensitive easy to use, long self-life, mass manufacturable and disposable. Fluorescence assay approach has been developed potential substitute to conventional techniques used in enzyme's quantification. The fluorescent probes possess excellent stability, high spatiotemporal ratio and reproducibility represent applications in real sample analysis. Therefore, the enzymatic transformations have been monitored by small activatable organic fluorescent probes. These probes are generally integrated with enzyme's substrate/inhibitors to improve their binding affinity toward the enzyme's catalytic site. As the recognition unit bio catalyzed, the signaling unit produces the readout signals and provides novel insights to understand the biochemical reactions for diagnosis and development of point of care devices. Several structural modifications are required in fluorogenic scaffolds to tune the selectivity for a particular enzyme. Hence, the fluorescent probes with their structural features and enzymatic reaction mechanism of oxidoreductase are the key points discussed in this review. The basic strategies to detect each enzyme are discussed. The selectivity, sensitivity and real-time applications are critically compared. The kinetic parameters and futuristic opportunities are present, which would be enormous benefits for chemists and biologists to understand the facts to design and develop unique fluorophore molecules for clinical applications.

Gut microbiota mediates the absorption of FLZ, a new drug for Parkinson's disease treatment

The gut microbiota plays an important role in regulating the pharmacokinetics and pharmacodynamics of many drugs. FLZ, a novel squamosamide derivative, has been shown to have neuroprotective effects on experimental Parkinson's disease (PD) models. FLZ is under phase Ⅰ clinical trial now, while the underlying mechanisms contributing to the absorption of FLZ are still not fully elucidated. Due to the main metabolite of FLZ was abundant in feces but rare in urine and bile of mice, we focused on the gut microbiota to address how FLZ was metabolized and absorbed. In vitro studies revealed that FLZ could be exclusively metabolized to its major metabolite M1 by the lanosterol 14 alpha-demethylase (CYP51) in the gut microbiota, but was almost not metabolized by any other metabolism-related organs, such as liver, kidney, and small intestine. M1 was quickly absorbed into the blood and then remethylated to FLZ by catechol O-methyltransferase (COMT). Notably, dysbacteriosis reduced the therapeutic efficacy of FLZ on the PD mouse model by inhibiting its absorption. The results show that the gut microbiota mediate the absorption of FLZ through a FLZ-M1-FLZ circulation. Our research elucidates the vital role of the gut microbiota in the absorption of FLZ and provides a theoretical basis for clinical pharmacokinetic studies and clinical application of FLZ in the treatment of PD.

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.

Mixed azo dyes degradation by an intracellular azoreductase enzyme from alkaliphilic Bacillus subtilis: a molecular docking study

The rise of pollution due to the dye industries and textile wastes are evolving rapidly every day. The dyes are used in different trade names by the textile industries. The actual chemistry of dye is vague and difficult to understand even today though we are equipped technically. The toxic effects of the dyes and the reasons behind the acute toxicity are also an undiscovered mystery; therefore, no effective measures can be employed to degrade dyes. Deploying physical or chemical methods to pre-treat the azo dyes are expensive, extremely energy-consuming, and are not environment friendly. Hence, the use of microbes for textile dye degradation will be eco-friendly and is probably a cost-effective alternative to physicochemical methods. The present study was conducted to investigate the degradation of azo dyes isolated from textile effluent contaminated soil by employing the bacterial strains for degradation. The bacterial strains could degrade the optimum concentration of mixed azo dyes (200 mg/L) with an incubation up to 5 days. The decolourization of the dyes was expressed in terms of percentage of decolourization, and was found that about 87.35% of degradation by Bacillus subtilis strain. The enzyme responsible was analyzed as intracellular azoreductase involved in the degradation of mixed azo dyes. The enzymatic pathway and 1-phenyl-2-4(4-methyl phenyl)-diazene 1-oxide was observed as the major metabolite by GC-MS analysis. The in silico study determined the binding of mixed azo dye with azoreductase and hypothesized that their linking could be the main reason for the degradation of mixed azo dye.

Current Trends on Role of Biological Treatment in Integrated Treatment Technologies of Textile Wastewater

Wastewater discharge is a matter of concern as it is the primary source of water pollution. Consequently, wastewater treatment plays a key role in reducing the negative impact that wastewater discharge produce into the environment. Particularly, the effluents produced by textile industry are composed of high concentration of hazardous compounds such as dyes, as well as having high levels of chemical and biological oxygen demand, suspended solids, variable pH, and high concentration of salt. Main efforts have been focused on the development of methods consuming less water or reusing it, and also on the development of dyes with a better fixation capacity. However, the problem of how to treat these harmful effluents is still pending. Different treatment technologies have been developed, such as coagulation-flocculation, adsorption, membrane filtration, reverse osmosis, advanced oxidation, and biological processes (activated sludge, anaerobic-aerobic treatment, and membrane bioreactor). Concerning to biological treatments, even though they are considered as the most environmentally friendly and economic methods, their industrial application is still uncertain. On the one hand, this is due to the costs of treatment plants installation and, on the other, to the fact that most of the studies are carried out with simulated or diluted effluents that do not represent what really happens in the industries. Integrated treatment technologies by combining the efficiency two or more methodologies used to be more efficient for the decontamination of textile wastewater, than treatments used separately. The elimination of hazardous compounds had been reported using combination of physical, chemical, and biological processes. On this way, as degradation products can sometimes be even more toxic than the parent compounds, effluent toxicity assessment is an essential feature in the development of these alternatives. This article provides a critical view on the state of art of biological treatment, the degree of advancement and the prospects for their application, also discussing the concept of integrated treatment and the importance of including toxicity assays to reach an integral approach to wastewater treatment.

Remediation of textile effluents for water reuse: Decolorization and desalination using Escherichia fergusonii followed by detoxification with activated charcoal

Textile effluents contain high levels of pollutants of different categories like dyes, metal salts, acids, bases and microorganisms. Remediation of textile effluents is often challenging because of its composition, which also varies between dyeing units. In this study, we demonstrate the novel use of a waste-water bacterium, Escherichia fergusonii, in the effective remediation of textile effluents. The bacteria application efficiently caused a reduction of color (98.4%), total dissolved solids (75%), sulphates (87%), bicarbonates (83%), chlorides (64%), calcium (84%), and chemical oxygen demand (81%) of the textile effluents. The bacteria-treated effluents were further disinfected and detoxified by treating with rice husk activated charcoal. After the charcoal treatment, the chemical oxygen demand decreased further by 11.5% and biochemical oxygen demand decreased by 85%. The effluents remediated using the two-step process were subjected to toxicity assays using zebrafish (Danio rerio) model. The textile effluents treated using Escherichia fergusonii, followed by activated charcoal were found to be non-toxic and suitable for reuse for domestic applications. Thus, we present here, a simple, less energy-intensive, economic, two-step process as a complete solution for textile effluent treatment. The results of this investigation can be used to simplify the remediation process of textile effluents in common treatment plants as well as the individual dyeing units.

Degradation and Toxicity Analysis of a Reactive Textile Diazo Dye-Direct Red 81 by Newly Isolated Bacillus sp. DMS2

An efficient diazo dye degrading bacterial strain, Bacillus sp. DMS2 was isolated from a long-term textile dye polluted environment. The strain was assessed for its innate ability to completely degrade and detoxify Direct Red 81 (DR81) textile dye under microaerophilic conditions. The degradation ability of strain showed significant results on optimizing the nutritional and environmental parameters. Based on statistical models, maximum efficiency of decolorization achieved within 24 h for 100 mg/l of dye supplemented with glucose (0.02%), MgSO₄ (0.002%) and urea (0.5%) at 30°C and pH (7.0). Moreover, a significant catabolic induction of a laccase and azoreductase suggested its vital role in degrading DR81 into three distinct metabolites (intermediates) as by-products. Further, toxicity analysis of intermediates were performed using seeds of common edible plants, aquatic plant (phytotoxicity) and the nematode model (animal toxicity), which confirmed the non-toxic nature of intermediates. Thus, the inclusive study of DMS2 showed promising efficiency in bioremediation approach for treating industrial effluents.

Ecofriendly biodegradation of Reactive Black 5 by newly isolated Sterigmatomyces halophilus SSA1575, valued for textile azo dye wastewater processing and detoxification

A total of seven yeast strains from 18 xylanolytic and/or xylose-fermenting yeast species isolated from the wood-feeding termite Reticulitermes chinenesis could efficiently decolorize various azo dyes under high-salt conditions. Of these strains, a novel and unique azo-degrading and halotolerant yeast, Sterigmatomyces halophilus SSA1575, has been investigated in this study. This strain could significantly decolorize four combinations of a mixture of dyes. It showed a high capability for decolorizing Reactive Black 5 (RB5) even at 1,500 mg L⁻¹. The strain SSA1575 still showed a high capability for decolorizing a 50 mg L⁻¹ RB5 with a salt mixing at a NaCl concentration of up to 80 g L⁻¹. It also exhibited significant ability to decolorize repeated additions of dye aliquots, with a reduction in time of up to 18 h. Most of the tested carbon and nitrogen sources could significantly enhance a RB5 decolorization. However, this process was inhibited by the addition of sucrose and sodium nitrate. NADH-dichlorophenol indophenol (NADH-DCIP) reductase and lignin peroxidase were determined as the key reductase and oxidase of S. halophilus SSA1575. Finally, strain SSA1575, can effectively detoxify RB5 into non-toxic products. Overall, S. halophilus SSA1575, might be a promising halotolerant yeast valued for the treatment of various textile effluents with high salinity.

Heterologous expression of azoreductase-encoding gene azrS of Bacillus sp. MR-1/2 for enhanced azo dye decolorization and wastewater treatment

In Pakistan, 55% of textile exports are contributed by textile-units of Faisalabad. The effluents of these textile units, being discharged without any treatment, contain the contamination of a huge amount of synthetic azo dyes. The objective of the current research was to evaluate the contribution of an azoreductase-encoding gene (azrS) from a pre-characterized azo dye decolorizing bacterial strain Bacillus sp. MR-1/2 in a high copy number host system (pUC19-T7-Top-T) of Escherichia coli strain DH5α followed by in-silico prediction of azoreductase enzyme (AzrS) function. The recombinant cells that contained azrS had a significantly higher rate of color removal in congo red and reactive black-5 dyes when compared to wild-type MR-1/2 and E. coli DH5α after 72 h of incubation. Moreover, we were able to show that the recombinant strain significantly reduced the values of all tested parameters (pH, EC, turbidity, TSS, and COD) in actual wastewater. In support of our results, it was also predicted through bioinformatics analysis that the deduced azoreductase protein of strain MR-1/2 is linked with the dye decolorization ability of the strain through NAD(P)H-ubiquinone: oxidoreductase activity. Furthermore, we also found that the deduced protein resembled closely related proteins of protein databank in many features, yet some unique features were predicted in the enzyme activity of strain MR-1/2. It was concluded that the recombinant strain could be examined in pilot-scale experiments for textile wastewater treatment.