Advances in exopolysaccharides based bioremediation of heavy metals in soil and water: A critical review

Synchronous bioremediation of vanadium(V) and chromium(VI) using straw in a continuous-flow reactor

Vanadium (V) and chromium (Cr) are key resources widely used in industrial production. However, mining causes V(V) and Cr(VI) contamination in groundwater, posing health and environmental risks. Straw is an important byproduct and considered waste, however, it could be a solid carbon source. Therefore, the feasibility of V(V) and Cr(VI) bioremediation in groundwater was determined using straw as the carbon source in this study. A continuous-flow reactor able to resist fluctuations in pollutant concentrations in groundwater was constructed. V(V) and Cr(VI) were completely removed (100%, 10-34 d) in the reactor, and the maximum Cr(VI) removal rate from effluent was 1.19 mg/(L·h) (34-64 d). After long-term reactor operation (114 d), the V(V) and Cr(VI) removal rates reached almost 100%. Moreover, the formation of humus and tryptophan contributed to V(V) and Cr(VI) bioremediation. The extracellular polymeric substance content increased from 108.28 to 113.98 mg/g VSS, and combined with V(V) and Cr(VI) to reduce their concentrations. Moreover, functional microbes associated with heavy metal removal (Bacillus and Pseudobacteroides) and straw decomposition (Paludibacter) were found. The findings of this study offer empirical evidence that support the utilization of straw for mitigating composite heavy metal pollution, thereby laying a foundation for its practical engineering applications.

Herbicide-treated soil as a reservoir of beneficial bacteria: microbiome analysis and PGP bioinoculants in maize

BACKGROUND

Herbicides are integral to agricultural weed management but can adversely affect non-target organisms, soil health, and microbiome. We investigated the effects of herbicides on the total soil bacterial community composition using 16S rRNA gene amplicon community profiling. Further, we aimed to identify herbicide-tolerant bacteria with plant growth-promoting (PGP) capabilities as a mitigative strategy for these negative effects, thereby promoting sustainable agricultural practices.

RESULTS

A bacterial community analysis explored the effects of long-term S-metolachlor application on soil bacterial diversity, revealing that the herbicide's impact on microbial communities is less significant than the effects of temporal factors (summer vs. winter) or agricultural practices (continuous maize cultivation vs. maize-winter wheat rotation). Although S-metolachlor did not markedly alter the overall bacteriome structure in our environmental context, the application of enrichment techniques enabled the selection of genera such as Pseudomonas, Serratia, and Brucella, which were rare in metagenome analysis of soil samples. Strain isolation revealed a rich source of herbicide-tolerant PGP bacteria within the culturable microbiome fraction, termed the high herbicide concentration tolerant (HHCT) bacterial culture collection. Within the HHCT collection, we isolated 120 strains that demonstrated significant in vitro PGP and biocontrol potential, and soil quality improvement abilities. The most promising HHCT isolates were combined into three consortia, each exhibiting a comprehensive range of plant-beneficial traits. We evaluated the efficacy and persistence of these multi-strain consortia during 4-week in pot experiments on maize using both agronomic parameters and 16S rRNA gene community analysis assessing early-stage plant development, root colonization, and rhizosphere persistence. Notably, 7 out of 10 inoculated consortia partners successfully established themselves and persisted in the maize root microbiome without significantly altering host root biodiversity. Our results further evidenced that all three consortia positively impacted both seed germination and early-stage plant development, increasing shoot biomass by up to 47%.

CONCLUSIONS

Herbicide-treated soil bacterial community analysis revealed that integrative agricultural practices can suppress the effects of continuous S-metolachlor application on soil microbial diversity and stabilize microbiome fluctuations. The HHCT bacterial collection holds promise as a source of beneficial bacteria that promote plant fitness while maintaining herbicide tolerance.

Isolating and Identifying One Strain with Lead-Tolerant Fungus and Preliminary Study on Its Capability of Biosorption to Pb2

To obtain lead-resistant microorganisms as potential strains for bioremediation, in this study, a strain of fungus with high resistance to lead was isolated and domesticated from lead-contaminated soil, which was cultured and molecularly biologically identified as the genus Sarocladium Pb-9 (GenBank No. MK372219). The optimal incubation time of strain Pb-9 was 96 h, the optimal incubation temperature was 25 °C, and the optimal incubation pH was 7. The strain Pb-9 had a good adsorption effect on Pb2+ at a lead concentration of 2000 mg/L; scanning electron microscopy (SEM) observed that the spores of the Pb-9 strain appeared to be wrinkled and deformed under Pb2+ stress, and XRD analysis showed that the mycelium of Pb-9 adsorbed Pb2+; Fourier transform infrared spectroscopy (FTIR) analysis showed that the Pb-9 strain might produce substances such as esters and polysaccharides under the treatment of different Pb2+ concentrations. The above results showed that strain Pb-9 has good resistance and adsorption capacity to lead. Therefore, it has potential application value in the bioremediation of environmental heavy metal pollution, and this study provides a fundamental basis for the bioremediation of lead pollution in the environment.

Interaction of biochar with extracellular polymers of resistant bacteria restrains Pb(II) adsorption onto their composite: Macro and micro scale investigations

Pb(II) sequestration in extracellular polymers-biochar composites (EPS-BC) was explored using macroscopic models and microscopic technology. The results showed that the actual adsorption capacity of EPS-BC was 52.2% lower than the calculated capacity based on adsorption onto pure components due to the interaction of polysaccharide and amide group in extracellular polymers with biochar, which masked the reactive sites related to Pb(II) in EPS-BC. The bond of Pb-O (40.8%) and Pb-OOC (31.5%) mainly contributed to Pb(II) speciation on the EPS-BC surfaces. Furthermore, each Pb atom coordinated with 6O atoms in the first shell and with 0.5C atoms in the second shell, indicating that the carboxyl group in composite was complexed with Pb(II) as a monodentate inner-sphere structure. The findings provide an in-depth understanding of the adsorption mechanism of heavy metals by extracellular polymers coupled with biochar at molecular scale, guiding bioremediation with respect to heavy metal contamination.

Overexpression of PsMYB62 from Potentilla sericea confers cadmium tolerance in tobacco

Excessive cadmium (Cd) content in soil poses serious hazard to the survival and development of various organisms. Potentilla sericea, characterized by strong resistance and high utility value, is an excellent choice for urban ecological greening. Plant MYB transcription factors can participate in respondind to a variety of abiotic stresses such as heavy metals and salinity. In this study, PsMYB62 was transformed into tobacco by leaf disc infestation to obtain PsMYB62 overexpressing tobacco lines, and its mechanism in response to Cd stress was further investigated. The results showed that with Cd treatment, PsMYB62 overexpressing tobacco exhibited significantly higher net photosynthetic rate, stomatal conductance, transpiration rate, intercellular CO2 concentration, chlorophyll content, as well as enhanced activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase enzymes, along with increased levels of reduced glutathione, proline, and soluble protein compared to the control. Conversely, levels of O2- and H2O2, and malondialdehyde were markedly lower than those in the control(P<0.05). Moreover, the aboveground Cd content was notably higher in the control than in the transgenic lines, whereas the control was much lower than the transgenic lines in the belowground fraction, with Cd subcellular distribution ratios ranking as follows: cell wall fraction > soluble fraction > organelle fraction (P<0.05). The expression of NtHMA3, NtYSL, NtPDR4 and NtPDR5B were much lower in transgenic lines compared to the control, while NtNAS3, NtSOD, and NtGSH2 exhibited significantly higher expression. Consequently, this study provides genetic resources for molecular breeding of Cd-tolerant plants through genetic engineering and lays a theoretical foundation for the remediation of heavy metal-contaminated soil.

Types, synthesis pathways, purification, characterization, and agroecological physiological functions of microbial exopolysaccharides: A review

Exopolysaccharides (EPS), originating from various microbes, are essential bioproducts with widespread applications including packaging, biomedicine, wastewater treatment, cosmetics, agriculture, and food industries. Particularly, in the field of sustainable agriculture, microbial EPS have positive effects on plant growth and have gained considerable interest among agriculturists. However, few studies have elucidated the mechanisms of action of EPS in soil-microbe-plant interactions in agroecosystems. This review focuses on the sources and types of EPS, biosynthetic processes, factors affecting EPS yield, extraction and purification methods employed to produce microbial EPS, and structural characterization methods for EPS. Moreover, the agroecological physiological functions of microbial EPS with respect to promoting soil health (e.g., improving soil structure and fertility and repairing contaminated soil) and plant growth (e.g., plant growth and physiological metabolism under normal and stress conditions, such as salt, drought, heavy metals, and extreme temperatures) are critically highlighted. Furthermore, existing challenges and prospects for agricultural applications are discussed. This review demonstrates that the application of microbial EPS in agriculture provides a new type of green material for agricultural producers to improve soil quality, increase agricultural productivity, and provide new ideas for sustainable agricultural development.

Exopolysaccharide-Producing Bacteria Regulate Soil Aggregates and Bacterial Communities to Inhibit the Uptake of Cadmium and Lead by Lettuce

The accumulation of heavy metals in the soil not only causes serious damage to the soil ecosystem, but also threatens human health through the food chain. Exopolysaccharides have the functions of adsorbing and chelating heavy metals and reducing their bioavailability in the soil. In our study, exopolysaccharide-producing bacteria with a high efficiency in adsorbing cadmium (Cd) and lead (Pb) were screened from heavy metal-contaminated farmland. Through pot experiments, the influence of functional strains on the size distribution, heavy metal content, and bacterial community structure of soil aggregates in lettuce was studied using high-throughput sequencing technology. The results show that 11 strains secreting exopolysaccharides were initially screened from heavy metal-contaminated soil. Among them, strain Z23 had a removal rate of 88.6% for Cd and 93.2% for Pb. The rate at which Cd was removed by strain Z39 was 92.3%, and the rate at which Pb was removed was 94.4%. Both strains belong to Bacillus sp. Strains Z23 and Z39 induced the formation of Fe2Pb(PO4)2, Cd2(PO4)2, and Pb2O3 in the solution. The pot experiments showed that strains Z23 and Z39 increased (19.1~23.9%) the dry weight and antioxidant enzyme activity of lettuce roots and leaves, while reducing (40.1~61.7%) the content of Cd and Pb. Strains Z23 and Z39 increased the proportion of microaggregates (<0.25 mm) and the content of exopolysaccharides in rhizosphere soil and reduced (38.4-59.7%) the contents of available Cd and Pb in microaggregates, thus inhibiting the absorption of heavy metals by lettuce. In addition, the exopolysaccharide content and the bacterial community associated with heavy metal resistance and nitrogen (N) cycling (Patescibacteria, Saccharimonadales, Microvirga, and Pseudomonas) in microaggregates were key factors affecting the available heavy metal content in soil. These results show that the exopolysaccharide-producing bacteria Z23 and Z39 reduced the absorption of Cd and Pb by lettuce tissues, thus providing strain resources for the safe utilization of soils that exceed heavy metal standards for farmland and for reducing the heavy metal content in vegetables.

Mechanism and application of bacterial exopolysaccharides: An advanced approach for sustainable heavy metal abolition from soil

The escalation of heavy metal pollutants in soils and effluents, driven by industrialization and human activities, poses significant environmental and health risks. Conventional remediation methods are often costly and ineffective, prompting a shift towards sustainable alternatives such as biological treatments. Natural biosorbents, including microbial cells and their byproducts, have emerged as promising solutions. One such approach involves leveraging exopolysaccharides (EPS), complex high-molecular-weight biopolymers synthesized by microbes under environmental stress conditions. EPS are intricate organic macromolecules comprising proteins, polysaccharides, uronic acids, humic compounds, and lipids, either located within microbial cells or secreted into their surroundings. Their anionic functional groups enable efficient electrostatic binding of cationic heavy metals, making EPS effective biosorbents for soil remediation. This review thoroughly explores the pivotal role of bacterial EPS in the removal of heavy metals, focusing on EPS biosynthesis mechanisms, the dynamics of interaction with heavy metals, and case studies that illustrate their effectiveness in practical remediation strategies. By highlighting these aspects, the review underscores the innovation and practical implications of EPS-based bioremediation technologies, demonstrating their potential to address critical environmental challenges effectively while paving the way for sustainable environmental management practices. Key findings reveal that EPS exhibit robust metal-binding capacities, facilitated by their anionic functional groups, thereby offering a promising solution for mitigating metal pollution in diverse environmental matrices.

The Marine-Origin Exopolysaccharide-Producing Bacteria Micrococcus Antarcticus HZ Inhibits Pb Uptake in Pakchoi (Brassica chinensis L.) and Affects Rhizosphere Microbial Communities

Exopolysaccharides (EPSs) produced by microorganisms play an important role in biotolerance and reducing heavy metal (HM) contamination by limiting the migration of HMs into plants. However, research on the application of EPS-producing marine bacteria for soil heavy metal remediation remains limited, particularly regarding their mechanisms of HM immobilization in soil and impact on plant growth. In this study, the EPS-producing marine bacterium Micrococcus antarcticus HZ was investigated for its ability to immobilize Pb and produce EPSs in soil filtrate. The effects on the growth quality and biomass of pakchoi (Brassica chinensis L.), as well as bacterial communities in inter-root soil contaminated with Pb, were also investigated. The results indicated that HZ could reduce the Pb concentration in the soil filtrate, achieving a removal rate of 43.25-63.5%. The EPS content and pH levels increased in the presence of Pb. Pot experiments showed that adding HZ significantly increased the biomass of pakchoi (9.45-14.69%), vitamin C (Vc) (9.69-12.92%), and soluble protein content (22.58-49.7%). HZ reduced the Pb content in the roots (17.52-47.48%) and leaves (edible tissues) (43.82-52.83%) of pakchoi. HZ increased soil enzyme activities (alkaline phosphatase, dehydrogenase, and urease), and the contents of ammonium nitrogen and nitrate nitrogen. Additionally, HZ also increased the relative abundance of beneficial bacteria (e.g., Proteobacteria, Cyanobacteria, and Chlorobacteria) in the inter-root soil, which have prophylactic and heavy-metal fixation functions. In summary, HZ reduces effective Pb content in edible tissues, roots, and inter-root soil by regulating inter-root soil microbial community structure, increasing soil pH, nitrogen content, and soil enzyme activity, and altering dominant phylum abundance.

Evaluating the role of soil EPS in modifying the toxicity potential of the mixture of polystyrene nanoplastics and xenoestrogen, Bisphenol A (BPA) in Allium cepa L

The coexistence of emerging pollutants like nanoplastics and xenoestrogen chemicals such as Bisphenol A (BPA) raises significant environmental concerns. While the individual impacts of BPA and polystyrene nanoplastics (PSNPs) on plants have been studied, their combined effects are not well understood. This study examines the interactions between eco-corona formation, physicochemical properties, and cyto-genotoxic effects of PSNPs and BPA on onion (Allium cepa) root tip cells. Eco-corona formation was induced by exposing BPA-PSNP mixtures to soil extracellular polymeric substances (EPS), and changes were analyzed using 3D-EEM, TEM, FTIR, hydrodynamic diameter, and contact angle measurements. Onion roots were treated with BPA (2.5, 5, and 10 mgL-1) combined with plain, aminated, and carboxylated PSNPs (100 mgL-1), with and without EPS interaction. Toxicity was assessed via cell viability, oxidative stress markers (superoxide radical, total ROS, hydroxyl radical), lipid peroxidation, SOD and catalase activity, mitotic index, and chromosomal abnormalities. BPA alone increased cytotoxic and genotoxic parameters in a dose-dependent manner. BPA with aminated PSNPs exhibited the highest toxicity among the pristine mixtures, revealing increased chromosomal abnormalities, oxidative stress, and cell mortality with rising BPA concentrations. In-silico experiments demonstrated the relationship between superoxide dismutase (SOD), catalase enzymes, PSNPs, BPA, and their mixtures. EPS adsorption notably reduced cyto-genotoxic effects, lipid peroxidation, and ROS levels, mitigating the toxicity of BPA-PSNP mixtures.

Structural Characterization and Biological Properties Analysis of Exopolysaccharides Produced by Weisella cibaria HDL-4

An exopolysaccharide (EPS)-producing strain, identified as Weissella cibaria HDL-4, was isolated from litchi. After separation and purification, the structure and properties of HDL-4 EPS were characterized. The molecular weight of HDL-4 EPS was determined to be 1.9 × 10⁶ Da, with glucose as its monosaccharide component. Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) analyses indicated that HDL-4 EPS was a D-glucan with α-(1→6) and α-(1→4) glycosidic bonds. X-ray diffraction (XRD) analysis revealed that HDL-4 EPS was amorphous. Scanning electron microscope (SEM) and atomic force microscope (AFM) observations showed that HDL-4 EPS possesses pores, irregular protrusions, and a smooth layered structure. Additionally, HDL-4 EPS demonstrated significant thermal stability, remaining stable below 288 °C. It exhibited a strong metal ion adsorption activity, emulsification activity, antioxidant activity, and water-retaining property. Therefore, HDL-4 EPS can be extensively utilized in the food and pharmaceutical industries as an additive and prebiotic.

Biomedical engineering utilizing living photosynthetic cyanobacteria and microalgae: Current status and future prospects

Cyanobacteria are the only prokaryotes capable of performing oxygenic photosynthesis on Earth. Besides their traditional roles serving as primary producers, cyanobacteria also synthesize abundant secondary metabolites including carotenoids, alkaloids, peptides, which have been reported to possess medicinal potentials. More importantly, the advancement of synthetic biology technology has further expanded their potential biomedical applications especially using living/engineered cyanobacteria, providing promising and attractive strategies for future disease treatments. To improve the understanding and to facilitate future applications, this review aims to discuss the current status and future prospects of cyanobacterial-based biomedical engineering. Firstly, specific properties of cyanobacteria related with biomedical applications like their natural products of bioactive compounds and heavy metal adsorption were concluded. Subsequently, based on these properties of cyanobacteria, we discussed the progress of their applications in various disease models like hypoxia microenvironment alleviation, wound healing, drug delivery, and so on. Finally, the future prospects including further exploration of cyanobacteria secondary metabolites, the integration of bioactive compounds synthesized by cyanobacteria in situ with medical diagnosis and treatment, and the optimization of in vivo application were critically presented. The review will promote the studies related with cyanobacteria-based biomedical engineering and its practical application in clinical trials in the future.

Efficacy of exopolysaccharide in dye-laden wastewater treatment: A comprehensive review

The discharge of dye-laden wastewater into the water streams causes severe water and soil pollution, which poses a global threat to aquatic ecosystems and humans. A diverse array of microorganisms such as bacteria, fungi, and algae produce exopolysaccharides (EPS) of different compositions and exhibit great bioflocculation potency to sustainably eradicate dyes from water bodies. Nanomodified chemical composites of EPS enable their recyclability during dye-laden wastewater treatment. Nevertheless, the selection of potent EPS-producing strains and physiological parameters of microbial growth and the remediation process could influence the removal efficiency of EPS. This review will intrinsically discuss the fundamental importance of EPS from diverse microbial origins and their nanomodified chemical composites, the mechanisms in EPS-mediated bioremediation of dyes, and the parametric influences on EPS-mediated dye removal through sorption/bioflocculation. This review will pave the way for designing and adopting futuristic green and sustainable EPS-based bioremediation strategies for dye-laden wastewater in situ and ex situ.

Comprehensive review on recent trends and perspectives of natural exo-polysaccharides: Pioneering nano-biotechnological tools

Exopolysaccharides (EPSs), originating from various microbes, and mushrooms, excel in their conventional role in bioremediation to showcase diverse applications emphasizing nanobiotechnology including nano-drug carriers, nano-excipients, medication and/or cell encapsulation, gene delivery, tissue engineering, diagnostics, and associated treatments. Acknowledged for contributions to adsorption, nutrition, and biomedicine, EPSs are emerging as appealing alternatives to traditional polymers, for biodegradability and biocompatibility. This article shifts away from the conventional utility to delve deeply into the expansive landscape of EPS applications, particularly highlighting their integration into cutting-edge nanobiotechnological methods. Exploring EPS synthesis, extraction, composition, and properties, the discussion emphasizes their structural diversity with molecular weight and heteropolymer compositions. Their role as raw materials for value-added products takes center stage, with critical insights into recent applications in nanobiotechnology. The multifaceted potential, biological relevance, and commercial applicability of EPSs in contemporary research and industry align with the nanotechnological advancements coupled with biotechnological nano-cleansing agents are highlighted. EPS-based nanostructures for biological applications have a bright future ahead of them. Providing crucial information for present and future practices, this review sheds light on how eco-friendly EPSs derived from microbial biomass of terrestrial and aquatic environments can be used to better understand contemporary nanobiotechnology for the benefit of society.

Metagenomic assembled genomes indicated the potential application of hypersaline microbiome for plant growth promotion and stress alleviation in salinized soils

Climate change is causing unpredictable seasonal variations globally. Due to the continuously increasing earth's surface temperature, the rate of water evaporation is enhanced, conceiving a problem of soil salinization, especially in arid and semi-arid regions. The accumulation of salt degrades soil quality, impairs plant growth, and reduces agricultural yields. Salt-tolerant, plant-growth-promoting microorganisms may offer a solution, enhancing crop productivity and soil fertility in salinized areas. In the current study, genome-resolved metagenomic analysis has been performed to investigate the salt-tolerating and plant growth-promoting potential of two hypersaline ecosystems, Sambhar Lake and Drang Mine. The samples were co-assembled independently by Megahit, MetaSpades, and IDBA-UD tools. A total of 67 metagenomic assembled genomes (MAGs) were reconstructed following the binning process, including 15 from Megahit, 26 from MetaSpades, and 26 from IDBA_UD assembly tools. As compared to other assemblers, the MAGs obtained by MetaSpades were of superior quality, with a completeness range of 12.95%-96.56% and a contamination range of 0%-8.65%. The medium and high-quality MAGs from MetaSpades, upon functional annotation, revealed properties such as salt tolerance (91.3%), heavy metal tolerance (95.6%), exopolysaccharide (95.6%), and antioxidant (60.86%) biosynthesis. Several plant growth-promoting attributes, including phosphate solubilization and indole-3-acetic acid (IAA) production, were consistently identified across all obtained MAGs. Conversely, characteristics such as iron acquisition and potassium solubilization were observed in a substantial majority, specifically 91.3%, of the MAGs. The present study indicates that hypersaline microflora can be used as bio-fertilizing agents for agricultural practices in salinized areas by alleviating prevalent stresses.

IMPORTANCE

The strategic implementation of metagenomic assembled genomes (MAGs) in exploring the properties and harnessing microorganisms from ecosystems like hypersaline niches has transformative potential in agriculture. This approach promises to redefine our comprehension of microbial diversity and its ecosystem roles. Recovery and decoding of MAGs unlock genetic resources, enabling the development of new solutions for agricultural challenges. Enhanced understanding of these microbial communities can lead to more efficient nutrient cycling, pest control, and soil health maintenance. Consequently, traditional agricultural practices can be improved, resulting in increased yields, reduced environmental impacts, and heightened sustainability. MAGs offer a promising avenue for sustainable agriculture, bridging the gap between cutting-edge genomics and practical field applications.

Isolation and identification of metallotolerant bacteria with a potential biotechnological application

Mining has led to severe environmental pollution in countries with exhaustive mining production and inadequate industrial waste regulation. Microorganisms in contaminated sites, like mine tailings, have adapted to high concentrations of heavy metals, developing the capacity of reducing or removing them from these environments. Therefore, it is essential to thoroughly characterize bacteria present in these sites to find different ways of bioremediation. In this regard, in this study, an enrichment and isolation procedure were performed to isolate bacteria with lower nutritional requirements and high tolerance to Cu(II) and Fe(II) from two Sonoran River basin mining tails. Two Staphylococcus species and a Microbacterium ginsengisoli strain were isolated and identified from the San Felipe de Jesús mining tail. Also, three strains were isolated from the Nacozari de García mining tail: Burkholderia cenocepacia, Sphingomonas sp. and Staphylococcus warneri. Significant microbiological differences were found between the two sites. All these species exhibited tolerance up to 300 mg/L for Cu (II)-Fe (II) solutions, indicating their capacity to grow in these conditions. Moreover, a consortium of isolated bacteria was immobilized in two different biocomposites and the biocomposite with larger pore size achieved greater bacterial immobilization showcasing the potential of these bacteria in biotechnological applications.

Advanced oxidation process for the treatment of industrial wastewater: A review on strategies, mechanisms, bottlenecks and prospects

Due to its complex and, often, highly contaminated nature, treating industrial wastewater poses a significant environmental problem. Many of the persistent pollutants found in industrial effluents cannot be effectively removed by conventional treatment procedures. Advanced Oxidation Processes (AOPs) have emerged as a promising solution, offering versatile and effective means of pollutant removal and mineralization. This comprehensive review explores the application of various AOP strategies in industrial wastewater treatment, focusing on their mechanisms and effectiveness. Ozonation (O3): Ozonation, leveraging ozone (O3), represents a well-established AOP for industrial waste water treatment. Ozone's formidable oxidative potential enables the breakdown of a broad spectrum of organic and inorganic contaminants. This paper provides an in-depth examination of ozone reactions, practical applications, and considerations involved in implementing ozonation. UV/Hydrogen Peroxide (UV/H2O2): The combination of ultraviolet (UV) light and hydrogen peroxide (H2O2) has gained prominence as an AOP due to its ability to generate hydroxyl radicals (ȮH), highly efficient in pollutant degradation. The review explores factors influencing the efficiency of UV/H2O2 processes, including H2O2 dosage and UV radiation intensity. Fenton and Photo-Fenton Processes: Fenton's reagent and Photo-Fenton processes employ iron ions and hydrogen peroxide to generate hydroxyl radicals for pollutant oxidation. The paper delves into the mechanisms, catalyst selection, and the role of photoactivation in enhancing degradation rates within the context of industrial wastewater treatment. Electrochemical Advanced Oxidation Processes (EAOPs): EAOPs encompass a range of techniques, such as electro-Fenton and anodic oxidation, which employ electrode reactions to produce ȮH radicals. This review explores the electrochemical principles, electrode materials, and operational parameters critical for optimizing EAOPs in industrial wastewater treatment. TiO2 Photocatalysis (UV/TiO2): Titanium dioxide (TiO2) photocatalysis, driven by UV light, is examined for its potential in industrial wastewater treatment. The review investigates TiO2 catalyst properties, reaction mechanisms, and the influence of parameters like catalyst loading and UV intensity on pollutant removal. Sonolysis (Ultrasonic Irradiation): High-frequency ultrasound-induced sonolysis represents a unique AOP, generating ȮH radicals during the formation and collapse of cavitation bubbles. This paper delves into the physics of cavitation, sonolytic reactions, and optimization strategies for industrial wastewater treatment. This review offers a critical assessment of the applicability, advantages, and limitations of these AOP strategies in addressing the diverse challenges posed by industrial wastewater. It emphasizes the importance of selecting AOPs tailored to the specific characteristics of industrial effluents and outlines potential directions for future research and practical implementation. The integrated use of these AOPs, when appropriately adapted, holds the potential to achieve sustainable and efficient treatment of industrial wastewater, contributing significantly to environmental preservation and regulatory compliance.

Alpha-glucan: a novel bacterial polysaccharide and its application as a biosorbent for heavy metals

This study identified an extracellular bacterial polysaccharide produced by Bacillus velezensis strain 40B that contains more than 90% of the monosaccharide glucose as alpha-glucan. A prominent peak at 1074 cm-1, a characteristic of glycoside couplings, was visible in the FTIR spectrum. There were traces of xylose, sucrose, and lactose, according to the HPLC study. The ability of this bacterial glucan to operate as a biosorbent of the heavy metals cobalt, chromium, copper, and lead from aqueous solutions was investigated in conjunction with Ca-alginate beads. It proved that glucan 40B has a low affinity for chromium ions and is selective for lead. Initial concentration measurements showed an inverse relationship between concentration and the amount of metal ions eliminated. Lead and chromium removal increased as the glucan dose was increased. It was shown that as the pH of the starting solution is elevated, there is an increase in the sorption of metal ions onto the glucan. It was clear that when the temperature increased, the fraction of metal ion sorption slightly increased. Glucan has a wide range of industrial applications, from food and medicine to health and nutrition. As a result, the investigation's scope was expanded to include heavy metal removal.

A mini-review on indigenous microbial biofilm from various wastewater for heavy-metal removal - new trends

Biofilm, as a form of the microbial community in nature, represents an evolutionary adaptation to the influence of various environmental conditions. In nature, the largest number of microorganisms occur in the form of multispecies biofilms. The ability of microorganisms to form a biofilm is one of the reasons for antibiotic resistance. The creation of biofilms resistant to various contaminants, on the other hand, improves the biological treatment process in wastewater treatment plants. Heavy metals cannot be degraded, but they can be transformed into non-reactive and less toxic forms. In this process, microorganisms are irreplaceable as they interact with the metals in a variety of ways. The environment polluted by heavy metals, such as wastewater, is also a source of undiscovered microbial diversity and specific microbial strains. Numerous studies show that biofilm is an irreplaceable strategy for heavy metal removal. In this review, we systematize recent findings regarding the bioremediation potential of biofilm-forming microbial species isolated from diverse wastewaters for heavy metal removal. In addition, we include some mechanisms of action, application possibilities, practical issues, and future prospects.

Exopolysaccharides of Serratia fonticola CPSE11 can alleviate the toxic effect of Cd2+ on Codonopsis pilosula

In order to study the detoxification effect of microbial exopolysaccharides (EPS) on the heavy metal cadmium (Cd2+), this study took an EPS-producing Serratia fonticola CPSE11 (NZ_CP050171.1) isolated from Codonopsis pilosula root as the research object. The whole genome and EPS synthesis gene clusters of this strain were predicted and analyzed, the adsorption kinetics of EPS on Cd2+ were studied by using pseudo-first-order and second-order kinetic equations, the isothermal adsorption curves were simulated and analyzed by using the Langmuir isothermal adsorption equation, and the effects of Cd2+ and EPS on the growth of C. pilosula were explored by seed germination experiment and hydroponic experiment. The analysis revealed that this strain contained three gene clusters related to EPS synthesis, and the metabolic pathway for EPS synthesis was obtained on the basis of the whole genome analysis and microbial physiological metabolism. The molecular weight and monosaccharide composition of EPS were determined by HPLC analysis, which showed that EPS consisted of mannose, glucosamine, rhamnose, galactosamine, glucose, and galactose with a molar ratio of 1:1.74:4.57:3.96:14.04:10.28, with the molecular weight of 366,316.09 kDa. The adsorption process of EPS on Cd2+ was in accordance with the second-order kinetic model, and the results of seed germination experiments showed that EPS could promote seed germination and improve seed activity. In the hydroponic experiment, high concentration of Cd2+ (15 mg/L) caused toxic symptoms in C. pilosula, while the addition of EPS reduced the toxic effect of Cd2+ on C. pilosula, and the plant growth was significantly improved.

Insight into the roles of soluble, loosely bound and tightly bound extracellular polymeric substances produced by Enterobacter sp. in the Cd2+ and Pb2+ biosorption process: Characterization and mechanism

Extracellular polymeric substances (EPSs) are macromolecular polymers formed by metabolic secretion, and they have great potential for removing heavy metal (HM) ions from the aquatic phase. In this study, the contributions of soluble EPSs (S-EPSs), loosely bound EPSs (LB-EPSs) and tightly bound EPSs (TB-EPSs) secreted by Enterobacter sp. to Cd²⁺ and Pb²⁺ adsorption were analyzed. The results indicated that in a solution containing both Cd²⁺ and Pb²⁺, pH= 6.0 was best suited for the adsorption process, and adsorption equilibrium was reached in approximately 120 min. Moreover, the mechanism for adsorption of Cd²⁺ and Pb²⁺ by the different layers of EPSs involved spontaneous chemical processes. However, Cd²⁺ adsorption by the three layers of the EPSs was an exothermic process (∆H⁰ <0), but Pb²⁺ adsorption by the three layers of the EPSs was an endothermic process (∆H⁰ >0). The variations in zeta potentials indicated that ion exchange occurred during Cd²⁺ and Pb²⁺ adsorption. FT-IR, XPS and 3D-EEM analyses indicated that the functional groups of the EPSs involved in adsorption were mainly the CO, C-O and C-O-C groups of the polysaccharides; furthermore, fulvic acid-like substances, humic-like substances and tyrosine-like proteins played important roles in the adsorption of Cd²⁺ and Pb²⁺ by the different EPS layers.

Culturable heterotrophic bacterial diversity study from an Indian lignite mine habitat

Diversity lifts the productivity of any ecosystem as all the species have a vital role to play that is present within the ecosystem. The characterization is essential to delve into the ecological functions of microbial communities and discover the type of microorganisms present within the ecosystem. As microbial diversity in ecosystems responds to environmental disturbances, it functions as a marker to indicate the change in such ecosystems. Mine ecology differs significantly from other habitats due to the presence of acidic runoff. This paper provides insight into the diversity of cultivable bacteria isolated from lignite mines located in south Gujarat. A total of 67 heterotrophic isolates were successfully cultivated from the collected solid and water samples of the Rajpardi and Tadkeshwar Lignite mine sites. The isolates were characterized morphologically and biochemically, and intra- and extracellular enzyme synthesis were studied. Moreover, the relative density and frequency of cultivated isolates from the samples were calculated. The similarity and evenness of the heterotrophic isolated were studied by calculating diversity indices such as Shannon and Simpson. Alpha diversity was calculated in PAST software to analyse the similarity between the selected two mine sites. This research also explored the relationship between the variance in heterotrophic microbial diversity and substrate utilization richness of the studied lignite mines of Gujarat.

Breeding, Biosorption Characteristics, and Mechanism of a Lead-Resistant Strain

To effectively carry out the bioremediation of a Pb²⁺ polluted environment, a lead-tolerant strain named D1 was screened from the activated sludge of a factory in Hefei, and its lead removal in a solution with Pb²⁺ concentration of 200 mg/L could reach 91% under optimal culture conditions. Morphological observation and 16S rRNA gene sequencing were used to identify D1 accurately, and its cultural characteristics and lead removal mechanism were also preliminarily studied. The results showed that the D1 strain was preliminarily identified as the Sphingobacterium mizutaii strain. The experiments conducted via orthogonal test showed that the optimal conditions for the growth of strain D1 were pH 7, inoculum volume 6%, 35 °C, and rotational speed 150 r/min. According to the results of scanning electron microscopy and energy spectrum analysis before and after the D1 exposure to lead, it is believed that the lead removal mechanism of D1 is surface adsorption. The Fourier transform infrared spectroscopy (FTIR) results revealed that multiple functional groups on the surface of the bacterial cells are involved in the Pb adsorption process. In conclusion, the D1 strain has excellent application prospects in the bioremediation of lead-contaminated environments.

Biological activities and applications of exopolysaccharides produced by lactic acid bacteria: a mini-review

Exopolysaccharides (EPSs) are naturally occurring high-molecular-weight carbohydrates that have been widely studied for their biological activities, including antioxidant, immunomodulatory, anticancer and gut microbiota regulation activities. Polysaccharides are abundant in nature and can be derived from animals, plants, algae, and microorganisms, but among polysaccharides with potential uses, EPSs from microorganisms have the advantages of a short production cycle, high yield, and independence of production from season and climate and thus have broad prospects. While the safety of the producing microorganism can represent a problem in application of microbial EPSs, lactic acid bacteria (LAB) have been used by humans for thousands of years, and they and their products are generally recognized as safe. This makes LAB excellent sources for exopolysaccharides. EPS-producing LAB are readily found in nature. Through screening of strains, optimization of culture conditions, and improvement of the growth medium, the yield of EPSs from LAB can be increased and the scope of application broadened. This review summarizes EPSs from LAB in terms of structure, function and applications, as well as yield optimization, and introduces recent research on the biological activities and practical applications of LAB EPSs, aiming to provide references for researchers in related areas.

Critical review on biogeochemical dynamics of mercury (Hg) and its abatement strategies

Mercury (Hg) is among the naturally occurring heavy metal with elemental, organic, and inorganic distributions in the environment. Being considered a global pollutant, high pools of Hg-emissions ranging from >6000 to 8000 Mg Hg/year get accumulated by the natural and anthropogenic activities in the atmosphere. These toxicants have high persistence, toxicity, and widespread contamination in the soil, water, and air resources. Hg accumulation inside the plant parts amplifies the traces of toxic elements in the linking food chains, leads to Hg exposure to humans, and acts as a potential genotoxic, neurotoxic and carcinogenic entity. However, excessive Hg levels are equally toxic to the plant system and severely disrupt the physiological and metabolic processes in plants. Thus, a plausible link between Hg-concentration and its biogeochemical behavior is highly imperative to analyze the plant-soil interactions. Therefore, it is requisite to bring these toxic contaminants in between the acceptable limits to safeguard the environment. Plants efficiently incorporate or absorb the bioavailable Hg from the soil thus a constructive understanding of Hg uptake, translocation/sequestration involving specific heavy metal transporters, and detoxification mechanisms are drawn. Whereas recent investigations in biological remediation of Hg provide insights into the potential associations between the plants and microbes. Furthermore, intense research on Hg-induced antioxidants, protein networks, metabolic mechanisms, and signaling pathways is required to understand these bioremediations techniques. This review sheds light on the mercury (Hg) sources, pollution, biogeochemical cycles, its uptake, translocation, and detoxification methods with respect to its molecular approaches in plants.

Production and characterization of exopolysaccharides from salinity-induced Auxenochlorella protothecoides and the analysis of anti-inflammatory activity

The set scenario of this work was to investigate the production, physicochemical characteristics, and anti-inflammatory activities of exopolysaccharides from salinity-induced Auxenochlorella protothecoides. The results demonstrated that 10 ‰ salinity manipulation endowed preferable exopolysaccharide production by A. protothecoides. Under this salinity stress, ACPEPS1A and ACPEPS2A were purified from exopolysaccharide production by anion chromatography and molecular exclusion chromatography. ACPEPS1A exhibited a molecular weight (Mw) of 132 kDa and mainly consisted of galactose. ACPEPS2A was a heteropolysaccharide with an Mw of 170 kDa and the main monosaccharides of galactose and rhamnose with separate molar percents of 42.41 % and 35.29 %, respectively. FTIR, ¹H and ¹³C NMR supported that monosaccharide components of ACPEPS1A and ACPEPS2A possessed both α- and β-configuration pyranose rings. Further evidence indicated that ACPEPS1A and ACPEPS2A could effectively inhibit the inflammatory response in lipopolysaccharide (LPS) induced RAW264.7 cells by quenching inflammatory factor levels such as ROS, iNOS, TNF-α, and IL-6. The potential anti-inflammatory possibilities were that the monosaccharides of ACPEPS1A and ACPEPS2A possessed higher affinity with receptors on the macrophage surface than LPS and hampered LPS-induced inflammation. The findings of this work would favor innovative applications of exopolysaccharides from microalgae in complementary medicines or functional foods.

Pb0 flue gas biosorption in denitrifying MBfR: Characteristics and binding ability of extracellular polymeric substances

Pb⁰ in flue gas which is ubiquitous in the environment, poses a certain threat to human and ecology, but the study on EPS-dependent stabilization of lead to remove Pb⁰ from flue gas remains insufficient. In this investigation, the characteristics and heavy metals-binding ability of four EPS fractions were evaluated. The EPS were extracted from denitrifying membrane biofilm reactor (MBfR) and divided into slime EPS (S-EPS), loosely-bound EPS (LB-EPS), tightly-bound EPS (TB-EPS) and EPS in circulating flow (Y-EPS). The S, LB, TB-EPS related to Pb stabilization on biofilm need more attention. Compared to Pb-S-EPS (0.013 mg g^-1) and Pb-LB-EPS (0.13 mg g^-1), the Pb-TB-EPS (0.26 mg g^-1) was mainly stable form of vapor Pb⁰, since TB-EPS's higher content (30.67-82.44 mg g^-1 VSS), proteins (13.47-36.32 mg g^-1 VSS) and polysaccharides (9.37-32.48 mg g^-1 VSS) concentration. Particularly, proteins related ligands were more effective in S, LB, TB-EPS dependent adsorption of Pb, complexing with hydrophobic acid ligands further strengthened in TB-EPS adsorption. The Pb-EPS complex formed via binding with functional groups (such as O-H, N-H, C-H and CC) on EPS, also facilitated by loose structure of proteins. This study enlightens the researchers on the bio-treatment and EPS-dependent biosorption of Pb⁰ in flue gas in denitrifying MBfR.

Recent advancements in cadmium-microbe interactive relations and their application for environmental remediation: a mechanistic overview

The toxic and persistent nature of cadmium (Cd) in the environment has become a matter of concern with its drastic increase in the concentrations over past few decades. Among the various techniques, the microbial remediation has been accepted as an effective decontamination tool for environmental applications, which is sustainable over a period of time. The Cd decontamination potential of the microbes depends on various internal and external factors that play a crucial role in selection of the microbes for application in a particular environment. Thus, it is important to understand the role of these factors for optimal application of the microbes. This study provides an insight into the mechanisms involved between the microbes and the environmental Cd. The study also briefly reviews the mathematical models that have been used to predict the remediation potential of the microbes and the kinetics involved during the process. A critical analysis of the recent advancements in the techniques for use of bacteria, fungi, and algal cells to remove Cd has been also presented in the manuscript.

Bioremediation of copper using indigenous fungi Aspergillus species isolated from an abandoned copper mine soil

Bioremediation of mining soils using metal tolerant fungi is widely considered as a promising cost-effective and ecofriendly approach. This study assessed the copper removal efficiency and bioaccumulation ability of the indigenous species Aspergillus hiratsukae LF1 and Aspergillus terreus LF2 isolated from the soils of an abandoned copper mine in Oman. Nutrient medium containing five different Cu (II) levels (0 - control, 100, 200, 300 and 500 mg/L) was employed for assessing both parameters. The removal efficiency from nutrient medium (100-500 mg Cu per L) ranged from 57% to 21% for A. hiratsukae LF1, and from 69% to 24% for A. terreus LF2. A. hiratsukae LF1 and A. terreus LF2 accumulated a maximum of 4.63 and 5.95 mg Cu/g,espectively, at 500 mg/L of Cu (II) concentration. The compositional analysis of extracellular polymeric substances excreted by both species revealed a hormetic response by A. hiratsukae LF1 at 100 mg/L; whereas increasing media Cu levels induced carbohydrates production in A. terreus LF2. These results hint at the involvement of carbohydrates in the Cu-tolerance mechanism of the latter. Copper accumulation in both species was further demonstrated through scanning electron microscopy and energy dispersive spectrometry. In line with the pertaining literature, our results are somewhat inconclusive concerning whether proteins or carbohydrates play a more pivotal role in copper complexation in both species; yet, FTIR analysis showed the participation of different functional groups in Cu sorption. Overall, although additional research is required to advance the knowledge about both Aspergillus species, our findings suggest that A. terreus LF2 presents greater promise for copper bioremediation due to enhanced tolerance and accumulation capacity.

Efficient Lead Pb(II) Removal with Chemically Modified Nostoc commune Biomass

A new biosorbent based on Nostoc commune (NC) cyanobacteria, chemically modified with NaOH (NCM), has been prepared, characterized and tested as an effective biomass to remove Pb(II) in aqueous media. The adsorption capacity of NCM was determined to be qe = 384.6 mg g−1. It is higher than several other biosorbents reported in the literature. Structural and morphological characterization were performed by FTIR, SEM/EDX and point zero of charge pH (pHPZC) measurements. NCM biosorbent showed more porous surfaces than those NC with heterogeneous plates including functional adsorption groups such as OH, C = O, COO−, COH or NH. Optimal Pb(II) adsorption occurred at pH 4.5 and 5.5 with a biomass dose of 0.5 g L−1. The experimental data of the adsorption process were well fitted with the Freundlich-isotherm model and pseudo-2nd order kinetics, which indicated that Pb(II) adsorption was a chemisorption process on heterogeneous surfaces of NCM. According to the thermodynamic parameters, this process was exothermic (∆H0 < 0), feasible and spontaneous (∆G0 < 0). NCM can be regenerated and efficiently reused up to 4 times (%D > 92%). NCM was also tested to remove Pb (%R~98%) and Ca (%R~64%) from real wastewater.

Mycosynthesis of Metal-Containing Nanoparticles-Fungal Metal Resistance and Mechanisms of Synthesis

In the 21st century, nanomaterials play an increasingly important role in our lives with applications in many sectors, including agriculture, biomedicine, and biosensors. Over the last two decades, extensive research has been conducted to find ways to synthesise nanoparticles (NPs) via mediation with fungi or fungal extracts. Mycosynthesis can potentially be an energy-efficient, highly adjustable, environmentally benign alternative to conventional physico-chemical procedures. This review investigates the role of metal toxicity in fungi on cell growth and biochemical levels, and how their strategies of resistance, i.e., metal chelation, biomineral formation, biosorption, bioaccumulation, compartmentalisation, and efflux of metals from cells, contribute to the synthesis of metal-containing NPs used in different applications, e.g., biomedical, antimicrobial, catalytic, biosensing, and precision agriculture. The role of different synthesis conditions, including that of fungal biomolecules serving as nucleation centres or templates for NP synthesis, reducing agents, or capping agents in the synthesis process, is also discussed. The authors believe that future studies need to focus on the mechanism of NP synthesis, as well as on the influence of such conditions as pH, temperature, biomass, the concentration of the precursors, and volume of the fungal extracts on the efficiency of the mycosynthesis of NPs.

A viable bioremediation strategy for treating paper and pulp industry effluents and assessing the prospect of resulted bacterial biomass as single cell protein (SCP) using indigenous bacterial species

Aim of this research was to treat the organics enriched Paper and Pulp Industry (PPI) effluents using multi-metal tolerant predominant indigenous bacterial species. In addition, assessing the potential of treated bacterial biomass as a single cell protein (SCP). The multi-metal tolerant Streptomyces tuirus OS1 was enumerated from the Paper and Pulp Industry (PPI) effluents was identified through standard molecular characterization. S. tuirus OS1 proficiently ameliorated organic contaminants in PPI effluent in the in study at 35 °C, 45 °C, and 25 °C. Fortunately, the S. tuirus OS1 considerably increased the dissolved oxygen level in treated PPI effluent in 30 days of bioremediation process. Interestingly, at 35 °C of bioremediation process the S. tuirus OS1 demonstrated increased dried biomass (7.1 g L^-1) with the total crude protein (SCP) as 5.3 g L^-1 (78.79%) in 30 days of bioremediation process. These findings suggest that S. tuirus OS1 is capable of reducing organic pollutants in PPI effluents and producing biomass with enriched protein content.

Longitudinal physiological and transcriptomic analyses reveal the short term and long term response of Synechocystis sp. PCC6803 to cadmium stress

Due to the bioaccumulation and non-biodegradability of cadmium, Cd can pose a serious threat to ecosystem even at low concentration. Microalgae is widely distributed photosynthetic organisms in nature, which is a promising heavy metal remover and an effective industrial sewage cleaner. However, there are few detailed reports on the short-term and long-term molecular mechanisms of microalgae under Cd stress. In this study, the adsorption behavior (growth curve, Cd removal efficiency, scanning electron microscope, Fourier transform infrared spectroscopy, and dynamic change of extracellular polymeric substances), cytotoxicity (photosynthetic pigment, MDA, GSH, H₂O₂, O₂^-) and stress response mechanism of microalgae were discussed under EC50. RNA-seq detected 1413 DEGs in 4 treatment groups. These genes were related to ribosome, nitrogen metabolism, sulfur transporter, and photosynthesis, and which been proved to be Cd-responsive DEGs. WGCNA (weighted gene co-expression network analysis) revealed two main gene expression patterns, short-term stress (381 genes) and long-term stress (364 genes). The enrichment analysis of DEGs showed that the expression of genes involved in N metabolism, sulfur transporter, and aminoacyl-tRNA biosynthesis were significantly up-regulated. This provided raw material for the synthesis of the important component (cysteine) of metal chelate protein, resistant metalloprotein and transporter (ABC transporter) in the initial stage, which was also the short-term response mechanism. Cd adsorption of the first 15 min was primary dependent on membrane transporter and beforehand accumulated EPS. Simultaneously, the up-regulated glutathione S-transferase (GSTs) family proteins played a role in the initial resistance to exogenous Cd. The damaged photosynthetic system was repaired at the later stage, the expressions of glycolysis and gluconeogenesis were up-regulated, to meet the energy and substances of physiological metabolic activities. The study is the first to provide detailed short-term and long-term genomic information on microalgae responding to Cd stress. Meanwhile, the key genes in this study can be used as potential targets for algae-mediated genetic engineering.

Microalgae as Potential Sources of Bioactive Compounds for Functional Foods and Pharmaceuticals

Microalgae are an untapped source of bioactive compounds with various biotechnological applications. Several species are industrially produced and commercialized for the feed or cosmetic industries, however, other applications in the functional food and pharmaceutical markets can be foreseen. In this study, nine industrial/commercial species were evaluated for in vitro antioxidant, calcium-chelating, anti-tumoral, and anti-inflammatory activities. The most promising extracts were fractionated yielding several promising fractions namely, of Tetraselmis striata CTP4 with anti-inflammatory activity (99.0 ± 0.8% reduction in TNF-α production in LPS stimulated human macrophages at 50 µg/mL), of Phaeodactylum Tricornutum with cytotoxicity towards cancerous cell lines (IC50 = 22.3 ± 1.8 μg/mL and 27.5 ± 1.6 μg/mL for THP-1 and HepG2, respectively) and of Porphyridium sp. and Skeletonema sp. with good chelating activity for iron, copper and calcium (IC50 = 0.047, 0.272, 0.0663 mg/mL and IC50 = 0.055, 0.240, 0.0850 mg/mL, respectively). These fractions were chemically characterized by GC–MS after derivatization and in all, fatty acids at various degrees of unsaturation were the most abundant compounds. Some of the species under study proved to be potentially valuable sources of antioxidant, metal chelators, anti-tumoral and anti-inflammatory compounds with possible application in the functional food and pharmaceutical industries.

The role of microplastics biofilm in accumulation of trace metals in aquatic environments

Microplastics are one of the major contaminants of aquatic nature where they can interact with organic and inorganic pollutants, including trace metals, and adsorb them. At the same time, after the microplastics have entered the aquatic environments, they are quickly covered with a biofilm - microorganisms which are able to produce extracellular polymeric substances (EPS) that can facilitate sorption of trace metals from surrounding water. The microbial community of biofilm contains bacteria which synthesizes EPS with antimicrobial activity making them more competitive than other microbial inhabitants. The trace metal trapping by bacterial EPS can inhibit the development of certain microorganisms, therefore, a single microparticle participates in complex interactions of the diverse elements surrounding it. The presented review aims to consider the variety of interactions associated with the adsorption of trace metal ions on the surface of microplastics covered with biofilm, the fate of such microplastics and the ever-increasing risk to the environment caused by the combination of these large-scale pollutants - microplastics and trace metals. Since aquatic pollution problems affect the entire planet, strict regulation of the production, use, and disposal of plastic materials is needed to mitigate the effects of this emerging pollutant and its complexes could have on the environment and human health.

Natural Polymers and Their Nanocomposites Used for Environmental Applications

The aim of this review is to bring together the main natural polymer applications for environmental remediation, as a class of nexus materials with advanced properties that offer the opportunity of integration in single or simultaneous decontamination processes. By identifying the main natural polymers derived from agro-industrial sources or monomers converted by biotechnology into sustainable polymers, the paper offers the main performances identified in the literature for: (i) the treatment of water contaminated with heavy metals and emerging pollutants such as dyes and organics, (ii) the decontamination and remediation of soils, and (iii) the reduction in the number of suspended solids of a particulate matter (PM) type in the atmosphere. Because nanotechnology offers new horizons in materials science, nanocomposite tunable polymers are also studied and presented as promising materials in the context of developing sustainable and integrated products in society to ensure quality of life. As a class of future smart materials, the natural polymers and their nanocomposites are obtained from renewable resources, which are inexpensive materials with high surface area, porosity, and high adsorption properties due to their various functional groups. The information gathered in this review paper is based on the publications in the field from the last two decades. The future perspectives of these fascinating materials should take into account the scale-up, the toxicity of nanoparticles, and the competition with food production, as well as the environmental regulations.

Hydrous ferric oxides (HFO's) precipitated from contaminated waters at several abandoned Sb deposits - Interdisciplinary assessment

The presented paper represents a comprehensive analysis of ochre sediments precipitated from Fe rich drainage waters contaminated by arsenic and antimony. Ochre samples from three abandoned Sb deposits were collected in three different seasons and were characterized from the mineralogical, geochemical, and microbiological point of view. They were formed mainly by poorly crystallized 2-line ferrihydrite, with the content of arsenic in samples ranging from 7 g·kg^-1 to 130 g·kg^-1 and content of antimony ranging from 0.25 g·kg^-1 up to 12 g·kg^-1. Next-generation sequencing approach with 16S RNA, 18S RNA and ITS markers was used to characterize bacterial, fungal, algal, metazoal and protozoal communities occurring in the HFOs. In the 16S RNA, the analysis dominated bacteria (96.2%) were mainly Proteobacteria (68.8%) and Bacteroidetes (10.2%) and to less extent also Acidobacteria, Actinobacteria, Cyanobacteria, Firmicutes, Nitrosprae and Chloroflexi. Alpha and beta diversity analysis revealed that the bacterial communities of individual sites do not differ significantly, and only subtle seasonal changes were observed. In this As and Sb rich, circumneutral microenvironment, rich in iron, sulfates and carbonates, methylotrophic bacteria (Methylobacter, Methylotenera), metal/reducing bacteria (Geobacter, Rhodoferax), metal-oxidizing and denitrifying bacteria (Gallionella, Azospira, Sphingopyxis, Leptothrix and Dechloromonas), sulfur-oxidizing bacteria (Sulfuricurvum, Desulphobulbaceae) and nitrifying bacteria (Nitrospira, Nitrosospira) accounted for the most dominant ecological groups and their impact over Fe, As, Sb, sulfur and nitrogen geocycles is discussed. This study provides evidence of diverse microbial communities that exist in drainage waters and are highly important in the process of mobilization or immobilization of the potentially toxic elements.

Native Hyperaccumulator Plants with Differential Phytoremediation Potential in an Artisanal Gold Mine of the Ecuadorian Amazon

In tropical forests of southern Ecuador, artisanal gold mining releases heavy metals that become xenobiotic with indefinite circulation and eventual bioaccumulation. Restoration and rehabilitation of degraded mining sites represent a major ecological, technological and economic issue. In this study, we estimate the capacity of two native woody plants to accumulate cadmium (Cd), lead (Pb), zinc (Zn) and mercury (Hg), with the goal of developing effective strategies for phytoremediation of mining sites. Individuals of Erato polymnioides and Miconia sp., as well as their rhizospheric soils, were sampled from a natural zone (NZ) of montane cloud forest, used as a control, and a polluted zone (PZ) subjected to active gold mining. Concentrations of the four heavy metals were analyzed using atomic absorption spectrophotometry. Cd, Zn and Hg concentrations were higher in soils of PZ than NZ. Bioaccumulation (BCF) and translocation factors (TF) showed that Miconia sp. has potential for Cd and Zn phytostabilization, E. polymnioides has potential for Cd and Zn phytoextraction, and both species have potential for Hg phytoextraction. Despite the low productivity of these species, their adaptability to the edaphoclimatic conditions of the region and the possibility of using amendments to increase their biomass could compensate for the effectiveness of these species in reclaiming soils contaminated by mining.

Up-recycling oil produced water as the media-base for the production of xanthan gum

Produced water (PW) and crude glycerin (CG) are compounds overproduced by the oil and biodiesel industry and significant scientific efforts are being applied for properly recycling them. The aim of this research is to combine such industrial byproducts for sustaining the production of xanthan by Xanthomonas campestris. Xanthan yields and viscosity on distinct PW ratios (0, 10, 15, 25, 50, 100) and on 100% dialyzed PW (DPW) in shaker batch testing identified DPW treatment as the best approach for further bioreactor experiments. Such experiments showed a xanthan yield of 17.3 g/L within 54 h and a viscosity of 512 mPa s. Physical-chemical characterization (energy dispersive X-ray spectroscopy, scanning electron microscopy and Raman spectroscopy) showed similarities between the produced gum and the experimental control. This research shows a clear alternative for upcycling high salinity PW and CG for the generation of a valued bioproduct for the oil industry.

Identification and Characterization of Peruvian Native Bacterial Strains as Bioremediation of Hg-Polluted Water and Soils Due to Artisanal and Small-Scale Gold Mining in the Secocha Annex, Arequipa

The water and soils pollution due to mercury emissions from mining industries represents a serious environmental problem and continuous risk to human health. Although many strategies have been designed for the recovery or elimination of this metal from environmental sources, microbial bioremediation has proven to be the most effective and environmentally friendly strategy and thus control heavy metal contamination. The main objective of this work, using native bacterial strains obtained from contaminated soils of the Peruvian region of Secocha, was to identify which of these strains would have growth capacity on mercury substrates to evaluate their adsorption behavior and mercury removal capacity. Through a DNA analysis (99.78% similarity) and atomic absorption spectrometry, the Gram-positive bacterium Zhihengliuella alba sp. T2.2 was identified as the strain with the highest mercury removal capacity from culture solutions with an initial mercury concentration of 162 mg·L−1. The removal capacity reached values close to 39.5% in a period of incubation time of 45 days, with maximum elimination efficiency in the first 48 h. These results are encouraging and show that this native strain may be the key to the bioremediation of water and soils contaminated with mercury.

Contribution, Composition, and Structure of EPS by In Vivo Exposure to Elucidate the Mechanisms of Nanoparticle-Enhanced Bioremediation to Metals

Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS-metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L^-1) for 72 h. Cd-IONPs produced the highest concentrations of EPS proteins (136.3 mg L^-1), while Cd induced the most production of polysaccharides (241.0 mg L^-1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd-IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP-metal-EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP-metal-EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.

An overview of wind energy development and policy initiatives in India

The Indian renewable energy sector has grown at a compounded annual growth rate of 15.51% in the last five years, where wind growth is about 8%. The Indian government has been adopting changes to create a safe, cheap, and sustainable energy system to fuel vigorous economic growth. The government has made significant efforts in ensuring universal access to energy, giving power to its residents. It is implementing a large-scale deployment of renewable energy, particularly solar and wind. This paper examines the country's wind sector in-depth, including the government policy, financial incentives, and accomplishments. The study goes on to discuss the prospects and problems of the wind sector, as well as solutions to overcome them to reach the estimated target of 140-150 GW by 2030. Wind power growth in the country has weakened in the last few years which may hamper the country's ambitious renewable energy targets. Wind industry is facing several hindrances ranging from discontinuation of incentives, land acquisition, DISCOM's poor health, change in bidding scheme, old wind sites, etc. Certain steps, such as repowering outdated wind farms, giving generation-based incentives, tax concessions, reassessing the country's wind potential, and constructing competitive renewable energy zones could aid in reviving the wind energy sector.

Biosorption of Pb2+ and Zn2+ by Ca-alginate immobilized and free extracellular polysaccharides produced by Leuconostoc citreum B-2

AIMS

Heavy metal pollution seriously threatens human health and ecological environment. Due to high efficiency and excellent development prospect, adsorption technology has attracted worldwide attention. It is significant to develop renewable adsorbents with excellent adsorption performance.

SCOPE

In this study, the Pb²⁺ and Zn²⁺ adsorption capacity of Ca-alginate immobilized and free (without immobilization) Leu. citreum B-2 extracellular polysaccharides (EPS) was investigated. Isotherm and kinetic models were used to evaluate the adsorption performance. The adsorbents were characterized by SEM, FT-IR and XPS spectroscopy.

CONCLUSIONS

The maximum biosorption of Pb²⁺ 269.54 and Zn²⁺ 49.88 mg/g was achieved with immobilized EPS. Thermodynamic studies showed that the adsorption of Pb²⁺ and Zn²⁺ on EPS was a spontaneous and feasible process, and the adsorption properties of EPS were exothermic for lead and endothermic for zinc. All the adsorption processes conformed to the pseudo-second-order model and Langmuir adsorption isotherm model, indicating that the adsorption was mainly chemisorption taken placed on single adsorption surface. SEM results showed that the surface of EPS become denser after adsorption. FTIR and XPS analysis indicated that the adsorption mechanism mainly involved the complexation reaction and ion exchange of functional groups such as CO, O-C-O, -COOH and C-OH.

Effect of nano-TiO2 on humic acid utilization from piggery biogas slurry by microalgae

Resource recovery from piggery biogas slurry has become an inevitable demand for sustainable development of pig industry. Microalgae show great potential in recovering nitrogen and phosphorus from piggery slurry, but struggle to utilize organic pollutants, as most of them are inert components (e.g., humic acids, HAs). In this study, nano-TiO₂ was used to enhance the utilization of HAs by microalgae from piggery biogas slurry. Results showed that the optimal conditions for microalgal growth and HAs removal by the microalgae-TiO₂ coupling system were TiO₂ dosage of 0.30 g/L, microalgal inoculation concentration of 0.40 g/L, light intensity of 360 µmol photon/(m²·s) and temperature of 30 °C, with the microalgal chlorophyll concentration of 6.51 mg/L and HAs removal efficiency of 50.14%. Analysis of HAs composition variations in the piggery biogas slurry indicated that the decrease of HAs was caused by their decomposition into small molecules under the photocatalytic reactions of TiO₂.

Extremophilic Exopolysaccharides: Biotechnologies and Wastewater Remediation

Various microorganisms thrive under extreme environments, like hot springs, hydrothermal vents, deep marine ecosystems, hyperacid lakes, acid mine drainage, high UV exposure, and more. To survive against the deleterious effect of these extreme circumstances, they form a network of biofilm where exopolysaccharides (EPSs) comprise a substantial part. The EPSs are often polyanionic due to different functional groups in their structural backbone, including uronic acids, sulfated units, and phosphate groups. Altogether, these chemical groups provide EPSs with a negative charge allowing them to (a) act as ligands toward dissolved cations as well as trace, and toxic metals; (b) be tolerant to the presence of salts, surfactants, and alpha-hydroxyl acids; and (c) interface the solubilization of hydrocarbons. Owing to their unique structural and functional characteristics, EPSs are anticipated to be utilized industrially to remediation of metals, crude oil, and hydrocarbons from contaminated wastewaters, mines, and oil spills. The biotechnological advantages of extremophilic EPSs are more diverse than traditional biopolymers. The present review aims at discussing the mechanisms and strategies for using EPSs from extremophiles in industries and environment bioremediation. Additionally, the potential of EPSs as fascinating biomaterials to mediate biogenic nanoparticles synthesis and treat multicomponent water contaminants is discussed.