Halomonas sp. strain A55, a novel dye decolorizing bacterium from dye-uncontaminated Rift Valley Soda lake

Microbial diversity, transformation and toxicity of azo dye biodegradation using thermo-alkaliphilic microbial consortia

In this research, the transformation and toxicity of Reactive Red 141 and 239 biodegraded under anaerobic-aerobic conditions as well as metagenomic analysis of Reactive Red 239 degrading microbial consortia collected from Shala Hot spring were investigated. Toxicity of dyes before treatment and after treatment on three plants, fish and microorganisms were done. A halotolerant and thermo-alkaliphilic bacterial consortia decolorizing azo dyes (>98% RR 141 and > 96% RR 239 in 7 h) under optimum conditions of salt concentration (0.5%), temperature (55 °C) and pH (9), were used. Toxicity effect of untreated dyes and treated dyes in Tomato > Beetroot > Cabbage plants, while the effect was Leuconostoc mesenteroides > Lactobacillus plantarum > Escherichia coli in microorganisms. Among fishes, the toxicity effect was highest in Oreochromis niloticus followed by Cyprinus carpio and Clarias gariepinus. The three most dominant phyla that could be in charge of decolorizing RR 239 under anaerobic-aerobic systems were Bacteroidota (22.6-29.0%), Proteobacteria (13.5-29.0%), and Chloroflexi (8.8-23.5%). At class level microbial community structure determination, Bacteroidia (18.9-27.2%), Gammaproteobacteria (11.0-15.8%), Alphaproteobacteria (2.5-5.0%) and Anaerolineae (17.0-21.9%) were dominant classes. The transformation of RR 141 and RR 239 into amine compounds were proposed via high performance liquid chromatography-mass spectroscopy (HPLC/MS) and fourier transform infrared spectroscopy (FT-IR). Overall, dye containing wastewaters treated under anaerobic-aerobic systems using thermo-alkaliphilic microbial consortia were found to be safe to agricultural (fishes and vegetables) purposes.

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.

Evaluation of Osmotolerant Potential of Halomonas sulfidaeris MV-19 Isolated from a Mud Volcano

Salinity is one of the major challenges for cultivation of crops in a sustainable way because it severely affects plant growth and yield. Keeping this challenge in view, in the current study, a salt-tolerant Halomonas MV-19 was isolated from an extreme niche of mud volcano of Andaman Nicobar Island, India and identified on the basis of standard morphological, biochemical, and physiological tests and identified as Halomonas sulfidaeris strain MV-19 by 16S rRNA gene sequencing. The bacterium can grow on nutrient agar and nutrient broth supplemented with 3.5 M (≥ 20%) sodium chloride (NaCl). Sugar utilization assay revealed that H. sulfidaeris MV-19 utilizes only three sugars (dextrose, fructose, and mannose) from among twenty four tested sugars. The best growth of H. sulfidaeris MV-19 was observed in nutrient broth supplemented with 8% NaCl. When the broth was supplemented with dextrose, fructose, and mannose, the H. sulfidaeris MV-19 grew maximally in nutrient broth supplemented with 8% NaCl and 5% fructose. This strain produced exopolysaccharides (EPS) in nutrient broth supplemented with 8% NaCl and sugars (dextrose, fructose, and mannose). The EPS production was increased by 350% (three and half time) after addition of 5% fructose in nutrient broth compare with the EPS production in nutrient broth without supplemented with sugars. H. sulfidaeris MV-19 strain can produce EPS, which can help aggregate soil particle and reduced osmotic potential in soil, thus, be useful in alleviation of salinity stress in different crops cultivated in saline soils. The findings of the current investigation are expected to contribute towards effective abiotic stress management.

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.

Biomolecules from Serratia sp. CS1 indigenous to Ethiopian natural alkaline lakes: biosurfactant characteristics and assessment of compatibility in a laundry detergent

In this study, the biosurfactants (Bio-SFs) producing bacteria are screened from the selected alkaline lake of Ethiopia, and the potential bacterial strain and their produced Bio-SFs are further characterized. In an initial screening, 25 bacterial isolates were isolated, and among those, the bacterial isolate assigned as CS1 was identified as the most potent producer of Bio-SFs using a subsequent characterization process. The CS1 strain was identified as Serratia sp. via biochemical and molecular methods. An emulsion index (E₂₄) of 69.06 ± 0.11% was obtained for CS1 after 5 days of incubation time at 30 °C. The CS1-extracted Bio-SFs were characterized by Fourier transform infrared (FTIR), and it indicated that the type of biosurfactant produced was a glycolipid. The stability of the crude Bio-SFs was characterized, and the optimal conditions were found to be 80 °C, pH 8, and 3% NaCl, respectively. The extracted Bio-SFs were compatible with tested commercial detergents, and its efficiency increased from 12.2 ± 0.1% to 67.1 ± 0.17% and 70.43 ± 0.11% when combined with commercially available detergent brands in Ethiopia such as Taza and Largo, respectively. This study suggests that the isolated S. marcescens CS1 strain has the potential to produce Bio-SFs that are viable competence to replace the use of synthetic chemicals in the production of commercial detergents.

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.

Potential applications of halophilic microorganisms for biological treatment of industrial process brines contaminated with aromatics

Saline wastewater contaminated with aromatic compounds can be frequently found in various industrial sectors. Those compounds need to be degraded before reuse of wastewater in other process steps or release to the environment. Halophiles have been reported to efficiently degrade aromatics, but their application to treat industrial wastewater is rare. Halophilic processes for industrial wastewater treatment need to satisfy certain requirements: a continuous process mode, low operational expenditures, suitable reactor systems and a monitoring and control strategy. The aim of this review is to provide an overview of halophilic microorganisms, principles of aromatic biodegradation, and sources of saline wastewater containing aromatics and other contaminants. Finally, process examples for halophilic wastewater treatment and potential process monitoring strategies are discussed. To further illustrate the significant potential of halophiles for saline wastewater treatment and to facilitate development of ready-to-implement processes, future research should focus on scale-up and innovative process monitoring and control strategies.

Complete Genome Sequence of Halomonas sp. Strain SH5A2, a Dye-Degrading Halotolerant Bacterium Isolated from the Salinas and Aguada Blanca National Reserve in Peru

Halomonas sp. strain SH5A2 is a halotolerant bacterium isolated from Salinas Lake at 4,300 m above sea level in Peru. Here, we report its complete genome sequence with a length of 3,849,224 bp and highlight the presence of genes putatively related to dye degradation, such as NADPH-dependent oxidoreductases.

Halomonas sp. strain SH5A2 is a halotolerant bacterium isolated from Salinas Lake at 4,300 m above sea level in Peru. Here, we report its complete genome sequence with a length of 3,849,224 bp and highlight the presence of genes putatively related to dye degradation, such as NADPH-dependent oxidoreductases.

Decolorization and detoxification of azo dye by halo-alkaliphilic bacterial consortium: Systematic investigations of performance, pathway and metagenome

The high pH and salinity of textile wastewater is a major hindrance to azo dye decolorization. In this study, a mixed bacterial consortium ZW1 was enriched under saline (10% salinity) and alkaline (pH 10.0) conditions to decolorize Methanil Yellow G (MY-G). Consortium ZW1 was mainly composed of Halomonas (49.8%), Marinobacter (30.7%) and Clostridiisalibacter (19.2%). The effects of physicochemical factors were systematically investigated, along with the degradation pathway and metagenome analysis. The co-carbon source was found to be necessary, and the addition of yeast extract led to 93.3% decolorization of 100 mg/L MY-G within 16 h (compared with 1.12% for control). The optimum pH, salinity, temperature and initial dye concentration were 8.0, 5-10%, 40 °C and 100 mg/L, respectively. The typical dye-related degradation enzymes were most effective at 10% salinity. Consortium ZW1 was also able to differentially decolorize five other direct and acidic dyes in a short period. Phototoxicity tests revealed the detoxification of MY-G degradation products. Combining UV-vis, FTIR and GC-MS detection, the MY-G degradation pathway by consortium ZW1 was proposed. Furthermore, metagenomic approach was used to elucidate the functional potential of genes in MY-G biodegradation. These results signify the broad potential application of halo-alkaliphilic consortia in the bioremediation of dyeing wastewater.

Resuscitation, isolation and immobilization of bacterial species for efficient textile wastewater treatment: A critical review and update

Given highly complex and recalcitrant nature of synthetic dyes, textile wastewater poses a serious challenge on surrounding environments. Until now, biological treatment of textile wastewater using efficient bacterial species is still considered as an environmentally friendly and cost-effective approach. The advances in resuscitating viable but non-culturable (VBNC) bacteria via signaling compounds such as resuscitation-promoting factors (Rpfs) and quorum sensing (QS) autoinducers, provide a vast majority of potent microbial resources for biological wastewater treatment. So far, textile wastewater treatment from resuscitating and isolating VBNC state bacteria has not been critically reviewed. Thus, this review aims to provide a comprehensive picture of resuscitation, isolation and application of bacterial species with this new strategy, while the recent advances in synthetic dye decolorization were also elaborated together with the mechanisms involved. Discussion was further extended to immobilization methods to tackle its application. We concluded that the resuscitation of VBNC bacteria via signaling compounds, together with biochar-based immobilization technologies, may lead to an appealing biological treatment of textile wastewater. However, further development and optimization of the integrated process are still required for their wide applications.

Rift Valley Lake as a potential magnesium source to recover phosphorus from urine

Phosphorus recovery from urine is a sustainable approach. However, the challenge of this process is the accessibility of economically feasible magnesium sources. This study aimed to investigate the potential of low-cost Rift Valley Lake magnesium (RVL-Mg) source for phosphorus recovery from urine, where data is deficient in the source area. The effect of various operational conditions such as storage, Mg:P ratio (0.8-2.0), pH (5.5-10.5), mixing speed (30-180 rpm), urease enzyme addition (50-700 μL), urine dilution (0.11-9.0) and Ca:Mg ratio (0.3-2.5) was investigated. Under optimum operating conditions (M:P = 1.6, pH = 9, urease enzyme = 500 μL, mixing speed = 120 rpm, 60 min precipitation), the phosphorus removal efficiencies were >96% for actual and >98% for synthetic urine. During storage, spontaneous phosphorus losses were observed from synthetic (24.0%) and actual (32.0%) hydrolyzed urine due to precipitation with calcium and magnesium. The phosphorus recovery efficiency was reduced at higher (0.11:1) and lower (9:1) urine to RVL-Mg dilution, which is related to lower supersaturation of phosphorus and magnesium ions, respectively. Addition of calcium did not affect phosphorus removal efficiency, but the effect was significant on crystal product. With low (<1.0) Ca:Mg ratio, the crystal chemical analysis showed that the product has to be pure struvite (>99%), which was further identified by scanning electron microscope and X-ray diffraction to be quality struvite that might be used for agricultural purpose. Overall, low-cost magnesium ion collected from Rift Valley Lake can be a potentially candidate for sustainable phosphorus recovery from urine and any other phosphorus containing waste stream.

Azo dye decolorization by a halotolerant consortium under microaerophilic conditions

As a result of the use of a large amount of salt in dye industries, azo dye decolorization is often needed under hypersaline environments and low dissolved oxygen. Consortium GG-1, which is able to decolorize azo dyes in high salt concentrations and microaerophilic conditions, can be enriched using Metanil Yellow. Consortium GG-1 is mainly composed of Zobellella (62.25%), Rheinheimera (12.4%) and Marinobacterium (9.44%) and is able to decolorize azo dyes under 1%-10% salinity. The activities of azoreductase, laccase and lignin peroxidase were also measured. Together with the detected intermediates and the results obtained from FTIR, the decolorization process of Metanil Yellow was proposed. The influences of pH, initial concentration of azo dyes and concentration of yeast extract on the decolorization rate were also detected. Meanwhile, consortium GG-1 was identified with wide substrate specificity to dyes such as Direct Blue B, Acid Black ATT, and Acid Violet 7. Therefore, consortium GG-1 was identified with potential use in azo dye elimination.

Halomonas urmiana sp. nov., a moderately halophilic bacterium isolated from Urmia Lake in Iran

In the course of screening halophilic bacteria in Urmia Lake in Iran, which is being threatened by dryness, a novel Gram-negative, moderately halophilic, heterotrophic and short rod-shaped bacteria was isolated and characterized. The bacterium was isolated from a water specimen and designated as TBZ3^T. Colonies were found to be creamy yellow, with catalase- and oxidase-positive activities. The growth of strain TBZ3^T was observed to be at 10-45 °C (optimum, 30 °C), at pH 6.0-9.0 (optimum, pH 7.0) and in the presence of 0.5-20 % (w/v) NaCl (optimum, 7.5 %). Strain TBZ3^T contained C_16 : 0, cyclo-C_19 : 0  ω8c, summed feature 3 (comprising C_16 : 1  ω7c and/or C_16 : 1  ω6c) and summed feature 8 (comprising C_18 : 1  ω7c and/or C_18 : 1  ω6c) as major fatty acids and ubiquinone-9 as the only respiratory isoprenoid quinone. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, glycolipid, unidentified phospholipid and unidentified polar lipids were detected as the major polar lipids. Strain TBZ3^T was found to be most closely related to Halomonas saccharevitans AJ275^T , Halomonas denitrificans M29^T and Halomonas sediminicola CPS11^T with the 16S rRNA gene sequence similarities of 98.93, 98.15 and 97.60 % respectively and in phylogenetic analysis strain TBZ3^T grouped with Halomonas saccharevitans AJ275^T contained within a large cluster within the genus Halomonas. Based on phenotypic, chemotaxonomic and molecular properties, strain TBZ3^T represents a novel species of the Halomonas genus, for which the name Halomonas urmiana sp. nov. is proposed. The type strain is TBZ3^T (=DSM 22871^T=LMG 25416^T).

Hazardous waste treatment technologies

This is a review of the literature published in 2018 on topics related to hazardous waste management in water, soils, sediments, and air. The review covers treatment technologies applying physical, chemical, and biological principles for contaminated water, soils, sediments, and air. PRACTITIONER POINTS: The management of waters, wastewaters, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) was reviewed according to the technology applied, namely, physical, chemical and biological methods. Physical methods for the management of hazardous wastes including adsorption, coagulation (conventional and electrochemical), sand filtration, electrosorption (or CDI), electrodialysis, electrokinetics, membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, persulfate-based, Fenton and Fenton-like, and potassium permanganate processes for the management of hazardous were reviewed. Biological methods such as aerobic, anaerobic, bioreactor, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed.

Enhanced photoelectrocatalytic degradation of bisphenol A and simultaneous production of hydrogen peroxide in saline wastewater treatment

The degradation of organic pollutants in saline wastewater has been a challenge for environmental remediation. In this study, a two-chamber cell was structured to simultaneously degrade organic contaminants (bisphenol A, BPA) from saline wastewater and produce hydrogen peroxide (H₂O₂). In the anode chamber, a new solar-light-driven system was devised using chloride ions (Cl‾) as a medium and WO₃ photoanode as a radical initiator. Under solar light irradiation, photogenerated holes yielded at the WO₃ photoanode promoted the conversion of Cl‾ to reactive chlorine species, which could oxidize BPA more rapidly. The results indicated that the BPA removal can be significantly enhanced by increasing pH to 10.8 or increasing the Cl‾ concentration to 200 mM. At these conditions, 92% BPA was degraded into CO₂ and H₂O in 120 min. In the cathode chamber, a new dopamine modified carbon felt (CF-DPA) cathode was employed to produce H₂O₂, obtaining a high concentration of 5.4 mM under optimum conditions. The electrochemical analyses for CF-DPA revealed that dopamine modification promoted electron transfer and enhanced the two-electron oxygen reduction to increase H₂O₂ yields.

Treatments for color removal from wastewater: State of the art

It is evident from many recent papers that release of colored wastewater into the environment is source of pollution and this is a problem that particularly affect textile, dyeing and food industries. The review: (i) presents an analysis of various mechanisms involved in the different processes for color removal; (ii) describes conveniences and disadvantages that may exist in adopting one type of treatment in spite of another; (iii) reports the results of approximately 180 experimental tests. Both examples of treatments already widely applied to the real scale and still in the experimental phase are reported. This work focuses on different types of chemical/physical, chemical, electrochemical and biological processes applied in the field of color removal from industrial wastewater. Common chemical/physical treatments such as coagulation/flocculation, adsorption and membrane filtration as well as chemical-type processes are discussed, both those that exploit the traditional oxidizing chemical agents such as Ozone, H₂O₂ and reactive based on chlorine and those based on the principle of advanced chemical oxidation. In particular, both Hydroxyl radical based Advanced Oxidation Processes (AOPs) and Sulfate radical based AOPs are reported. The most commonly used Electrochemical processes for the removal of color are also presented as well as biological treatments. Based on more than 200 papers, this review provides important information on the use, effectiveness, advantages and downsides of the various treatments aimed at removing the color from the wastewater with a look at the technologies still under development.