Bioremediation Applications Research Articles

Surface displayed MerR increases mercury accumulation by green microalga Chlamydomonas reinhardtii

Mercury is a highly toxic trace metal that can accumulate in aquatic ecosystems and when resent at high concentrations can pose risks to both aquatic life and humans consuming contaminated fish. This research explores the use of the metalloregulatory protein MerR, known for its high affinity and selectivity toward mercury, in a novel application. Through a cell surface engineering approach, MerR was displayed on cells of green alga Chlamydomonas reinhardtii. A hydroxyproline-rich GP1 protein was used as an anchor to construct the engineered strains GP1-MerR that expresses the fluorescent protein mVenus. The surface engineered GP1-MerR strain led up to five folds higher Hg2+ accumulation compared to the WT strain at concentration range from 10-9 to 10-7 M Hg2+. The binding of Hg2+ via MerR was specific and did not get significantly affected by major freshwater water quality variables such as Ca2+ and dissolved organic matter. The presence of other trace metals (Zn2+, Cu2+, Ni2+, Pb2+, Cd2+) in a same concentration range even resulted in 30–40 % increase in the accumulated Hg. Further, the engineered cells also demonstrated the ability to accumulate Hg2+ from the water extracts of the Hg-contaminated sediment samples. These results demonstrate a novel approach utilizing the cell surface display system in C. reinhardtii for its potential application in bioremediation.

Microbial Biopolymers: From Production to Environmental Applications—A Review

Industrial evolution and agricultural expansion, explained by continuing population growth, have rendered enormous problems for the world throughout the past few decades, primarily because of waste generation. To reduce environmental impact and dependence on fossil fuels, scientists have explored replacing synthetic polymers with environmentally friendly and sustainable alternatives in many emergent applications. In this regard, microbial biopolymers have gained special attention. Many biopolymers originating from various strains of bacteria, fungi, and algae have been reported and their possible applications have increased rapidly. This review focuses on the wide range of microbial biopolymers, their characteristics, and factors influencing their production. The present study also describes the environmental applications of microbial biopolymers. The use of these biopolymers is very attractive as a value-added and sustainable approach to wastewater treatment. By acting as adsorbents, coagulants, and flocculants as well as filters in membrane processes, microbial biopolymers shine as promising solutions beyond conventional methods. They can be integrated into various stages of the treatment process, further enhancing the efficiency of wastewater treatment methods. Microbial biopolymer applications in bioremediation and soil stabilization are also reviewed. Several studies have demonstrated the strong potential of biopolymers in soil improvement due to their ability to minimize permeability, eliminate heavy metals, stabilize soil, and limit erosion. Challenges related to scaling up and the downstream processing of microbial biopolymers, as well as its future perspectives in environmental applications, are also discussed.

Efficient Chitin Extraction from Shrimp Exoskeletons through Single-Step Fermentation by Pseudomonas aeruginosa QF50 and Serratia sp. QCS23

Chitin, an abundant biopolymer with potential applications in agriculture, medicine, and bioremediation, is conventionally extracted using chemical methods that have environmental disadvantages. This study investigates the extraction of chitin from Litopenaeus vannamei shrimp waste by one-step fermentation using the bacterial strains Pseudomonas aeruginosa QF50 and Serratia sp. QCS23. A total of 4 kg of shrimp waste was treated by fermentation with culture media enriched with different concentrations of glucose (1, 5, and 10%) for 7 days at 25 °C, followed by purification and characterization processes using infrared spectroscopy and X-ray diffraction. The results demonstrated an increase in the yield of crude chitin proportional to the glucose concentration, reaching a maximum of 76.81 ± 7.64% for Pseudomonas aeruginosa QF50 and 71.30 ± 1.16% for Serratia sp. QCS23. Both strains showed high efficiencies in deproteinization (80–87%) and demineralization, with significant improvements especially shown at high glucose concentrations. Structural characterization confirmed the presence of the spectral characteristics of α-chitin, with crystallinity indices of 81% and 71% for chitins obtained with Pseudomonas aeruginosa QF50 and Serratia sp. QCS23, respectively. This study concludes that single-step fermentation with Pseudomonas aeruginosa QF50 and Serratia sp. QCS23 is an effective and sustainable method for the extraction of high-quality chitin from shrimp exoskeleton waste, offering a promising alternative to traditional chemical methods.

Proteomics of Penicillium chrysogenum for a Deeper Understanding of Lead (Pb) Metal Bioremediation.

Penicillium chrysogenum (P. chrysogenum), a ubiquitous filamentous fungus, has demonstrated remarkable potential in the bioremediation of lead-contaminated environments. Its inherent tolerance and bioaccumulation capacity for lead (Pb), coupled with its relatively rapid growth rate, make it an attractive candidate for bioremediation applications. This study aims to identify the proteomic changes in P. chrysogenuminduced by Pb metal stress and unravel the roles of identified proteins in molecular mechanisms and cellular responses. Untargeted proteomic analysis was carried out using a two-dimensional difference in gel electrophoresis (2D-DIGE) coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). This study reported the identification of 43 statistically significant proteins (24 upregulated and 19 downregulated, ANOVA, p ≤ 0.05; fold change ≥1.5) in P. chrysogenum as a consequence of Pb treatment. Proteins were grouped according to their function into 18 groups from which 13 proteins were related to metabolism, 11 were related to cellular process and signaling, and 19 proteins were related to information storage and processing. The current study is considered the first report about the proteomics study of P. chrysogenum under Pb stress conditions, where upregulated proteins could better explain the mechanism of tolerance and Pb toxicity removal. Our research has provided a thorough understanding of the molecular and cellular processes involved in fungal-metal interactions, paving the way for the development of innovative molecular markers for heavy metal myco-remediation. To the best of our knowledge, this study of P. chrysogenum provides valuable insights toward growing research in comprehending the metal-microbe interactions. This will facilitate development of novel molecular markers for metal bioremediation.

Beyond methane, new frontiers in anaerobic microbial hydrocarbon utilizing pathways.

Alkanes, single carbon methane to long-chain hydrocarbons (e.g. hexadecane and tetradecane), are important carbon sources to anaerobic microbial communities. In anoxic environments, archaea are known to utilize and produce methane via the methyl-coenzyme M reductase enzyme (MCR). Recent explorations of new environments, like deep sea sediments, that have coupled metagenomics and cultivation experiments revealed divergent MCRs, also referred to as alkyl-coenzyme M reductases (ACRs) in archaea, with similar mechanisms as the C1 utilizing canonical MCR mechanism. These ACR enzymes have been shown to activate other alkanes such as ethane, propane and butane for subsequent degradation. The reversibility of canonical MCRs suggests that these non-methane-activating homologues (ACRs) might have similar reversibility, perhaps mediated by undiscovered lineages that produce alkanes under certain conditions. The discovery of these alternative alkane utilization pathways holds significant promise for a breadth of potential biotechnological applications in bioremediation, energy production and climate change mitigation.

Sealing solid agar in serum bottles for rapid isolation and long-term preservation of chemoautotrophic ammonia-oxidizing bacteria

Ammonia-oxidizing bacteria (AOB) are ubiquitous on the earth and have broad applications in bioremediation. However, the number of their species with standing in nomenclature and deposited in Microbial Culture Collections still remains low. Moreover, only a few novel species have been reported over the last decades. In this study, we sealed agar in serum bottles to develop a kind of solid agar plate with the oxygen concentration in the headspace maintained at low levels. By using these plates, eight AOB isolates including two novel species were obtained. When AOB cells were grown on the sealed solid agar plates, the time to form visible colonies was largely reduced and the maximum diameter of colonies reached 2 mm, which makes the process of AOB isolation rapid and efficient. Based on five AOB isolates, the headspace oxygen concentration had a significant influence on AOB growth either on solid plate or in liquid culture. Especially, when grown under 21 % O2, the number of colonies formed on solid agar plates was very low and sometimes no visible colony formed. Besides the application on AOB isolation, the sealed solid agar plate was also effective for the enumeration and preservation of AOB cells. When preserved under room temperature for more than ten months, the AOB colonies on the plate could still be recovered. This method provides a feasible way to isolate more novel AOB species from the environment and deposit more species in Microbial Culture Collections.

Role of Lactic Acid Bacteria in Insecticide Residue Degradation.

Lactic acid bacteria are gaining global attention, especially due to their role as a probiotic. They are increasingly being used as a flavoring agent and food preservative. Besides their role in food processing, lactic acid bacteria also have a significant role in degrading insecticide residues in the environment. This review paper highlights the importance of lactic acid bacteria in degrading insecticide residues of various types, such as organochlorines, organophosphorus, synthetic pyrethroids, neonicotinoids, and diamides. The paper discusses the mechanisms employed by lactic acid bacteria to degrade these insecticides, as well as their potential applications in bioremediation. The key enzymes produced by lactic acid bacteria, such as phosphatase and esterase, play a vital role in breaking down insecticide molecules. Furthermore, the paper discusses the challenges and future directions in this field. However, more research is needed to optimize the utilization of lactic acid bacteria in insecticide residue degradation and to develop practical strategies for their implementation in real-world scenarios.

Phenotypic characterization for bioremediation suitability of isolates from Southern Tunisian tannery effluent

Effluents from the leather tanning industry contain diverse pollutants, including hazardous heavy metals, posing threats to public health and the surrounding environment. Indigenous bacterial isolates can represent an eco-friendly approach for tannery wastewater treatment; however, phenotypic characterization is necessary to determine whether these strains are suitable for bioremediation. In the present study, we analyzed seven new Enterococcus faecium strains and two new Bacillus subtillis strains isolated from effluents from the Southern Tunisian Tannery (ESTT). We evaluated phenotypic features beneficial for bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities. Additionally, we examined characteristics naturally occurring in environmental bacteria but less desirable in strains selected for bioremediation, such as antibiotic resistances and pathogenicity indicators. The observed phenotypes were then compared with whole-genome analysis. We observed biofilm production in two slime-producing bacteria, B. licheniformis RLT6, and E. faecium RLT8. Hydrophobicity of E. faecium strains RLT1, RLT5, RLT8, and RLT9, as well as B. licheniformis RLT6 correlated positively with increasing ESTT concentration. Exoenzyme activities were detected in E. faecium strains RLT2, RLT4, and RLT7, as well as B. licheniformis RLT6. As anticipated, all strains exhibited common resistances to antibiotics and hemolysis, which are widespread in nature and do not hinder their application for bioremediation. Importantly, none of the strains exhibited the pathogenic hypermucoviscosity phenotype. To the best of our knowledge, this is the first report consolidating all these phenotypic characteristics concurrently, providing a complete overview of strains suitability for bioremediation. ImportanceThe study evaluates the bioremediation potential of seven Enterococcus faecium strains and two Bacillus subtillis strains isolated from the effluents from the Southern Tunisian tannery (ESTT), which pose threats to public health and environmental integrity. The analysis primarily examines the phenotypic traits crucial to bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities, as well as characteristics naturally occurring in environmental bacteria related to heavy metal resistance, such as antibiotic resistances. Several strains were found to have high bioremediation potential and exhibit only antibiotic resistances commonly found in nature, ensuring their application for bioremediation remains uncompromised. The results of the exhaustive phenotypic analysis are contrasted with the whole genome sequences of the nine strains, underscoring the appropriateness of these bacterial strains for eco-friendly interventions in tannery wastewater treatment.

The Role of Nitrate Supply in Bioactive Compound Synthesis and Antioxidant Activity in the Cultivation of Porphyra linearis (Rhodophyta, Bangiales) for Future Cosmeceutical and Bioremediation Applications.

Porphyra sensu lato has economic importance for food and pharmaceutical industries due to its significant physiological activities resulting from its bioactive compounds (BACs). This study aimed to determine the optimal nitrate dosage required in short-term cultivation to achieve substantial BAC production. A nitrate experiment using varied concentrations (0 to 6.5 mM) revealed optimal nitrate uptake at 0.5 mM in the first two days and at 3 and 5 mM in the last five days. Polyphenols and carbohydrates showed no differences between treatments, while soluble proteins peaked at 1.5 and 3 mM. Total mycosporine-like amino acids (MAAs) were highest in algae incubated at 5 and 6.5 mM, and the highest antioxidant activity was observed in the 5 mM, potentially related to the MAAs amount. Total carbon and sulfur did not differ between treatments, while nitrogen decreased at higher nitrate. This discovery highlights the nuanced role of nitrate in algal physiology, suggesting that biological and chemical responses to nitrate supplementation can optimize an organism's health and its commercially significant bioactive potential. Furthermore, given its ability to absorb high doses of nitrate, this alga can be cultivated in eutrophic zones or even in out-/indoor tanks, becoming an excellent option for integrated multi-trophic aquaculture (IMTA) and bioremediation.

Machine learning approach for the effectual production of a novel esterase and its application in bioremediation of dairy effluent

The present work intends to maximize the production of an industrially important novel esterase from Trichoderma harzianum using both machine learning and statistical approaches and its application in the bioremediation of dairy effluent. Significant medium compounds, such as almond oil, casein, NaH2PO4, and trace elements, were screened from a pool of carbon, nitrogen, oil and surfactant sources along with other micronutrients using a first order statistical design. The optimum value of screened parameters was found using response surface methodology that resulted in the maximum esterase production of 2985.31 U/L. Artificial neural network trained with the experimental response of RSM experiments coupled with genetic algorithm optimization technique has resulted in the maximum esterase production of 3256.73 U/L, which is 150-folds higher as compared to the unoptimized condition and also found to be the higher than the outcome of statistical optimization. Dairy effluent was used for the production of esterase as well as for its bioremediation. At 50% load, the maximum reduction in chemical oxygen demand and the production of esterase were observed to be 46.84% and 34.12 U/L, respectively. The COD reduction of diary effluent was modelled using Michaelis-Menten kinetics and the kinetic parameters, half saturation constant (Km) and maximum reaction rate (rmax) value were evaluated as 286.88 mg/L and 26.04 mg/L/d, respectively.

Biomolecular condensates of Chlorocatechol 1,2-Dioxygenase as prototypes of enzymatic microreactors for the degradation of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are molecules with two or more fused aromatic rings that occur naturally in the environment due to incomplete combustion of organic substances. However, the increased demand for fossil fuels in recent years has increased anthropogenic activity, contributing to the environmental concentration of PAHs. The enzyme chlorocatechol 1,2-dioxygenase from Pseudomonas putida (Pp 1,2-CCD) is responsible for the breakdown of the aromatic ring of catechol, making it a potential player in bioremediation strategies. Pp 1,2-CCD can tolerate a broader range of substrates, including halogenated compounds, than other dioxygenases. Here, we report the construction of a chimera protein able to form biomolecular condensates with potential application in bioremediation. The chimera protein was built by conjugating Pp 1,2-CCD to low complex domains (LCDs) derived from the DEAD-box protein Dhh1. We showed that the chimera could undergo liquid-liquid phase separation (LLPS), forming a protein-rich liquid droplet under different conditions (variable protein and PEG8000 concentrations and pH values), in which the protein maintained its structure and main biophysical properties. The condensates were active against 4-chlorocatechol, showing that the chimera droplets preserved the enzymatic activity of the native protein. Therefore, it constitutes a prototype of a microreactor with potential use in bioremediation.

Endophytic Microbial Diversity, Heavy Metal Accumulation, and Antimicrobial Properties of Avicennia marina from Saudi Arabia

This study comprehensively examined the Avicennia marina plant, a key species along the Red Sea coast of the Saudi Arabian Kingdom, focusing on its microbial, biochemical, and ecological aspects. Specimens, including leaves, seeds, and seedlings of Avicennia marina plant, were collected during the summer of 2021 from two distinct mangrove-abundant regions in Yanbu Governorate, Kingdom of Saudi Arabia. Analysis of the plant revealed significant heavy metal concentrations in its sediment, leaves, and seeds, with the sediment from region 1 recording metals such as Cr (40.202 ppm) and Se (30.522 ppm). Additionally, the plant’s extracts exhibited notable antimicrobial properties, inhibiting growth of several pathogenic bacteria, with ethyl acetate extracts from leaves being especially potent against strains like P. aeruginosa and S. aureus. Moreover, from the leaves collected in the Yanbu region, 10 unique endophytic bacterial species were identified. Utilizing genomic analysis tools, two of these bacteria were closely characterized, revealing more than 99% similarity to known bacterial species; Mixta and Cytobacillus species, emphasizing the microbial diversity within the mangrove leaves. In sum, Avicennia marina emerges as ecologically significant, with potential implications for bio-remediation and antimicrobial applications, and as a reservoir of diverse microbial species. With mounting global challenges, such as climate change, understanding these microbial-plant interactions is pivotal for both conservation and biotechnological pursuits in the future.

Reduction of selenite to selenium nanoparticles by highly selenite-tolerant bacteria isolated from seleniferous soil

The microbial reduction of selenite to elemental selenium nanoparticles (SeNPs) is thought to be an effective detoxification process of selenite for many bacteria. In this study, Metasolibacillus sp. ES129 and Oceanobacillus sp. ES111 with high selenite reduction efficiency or tolerance were selected for systematic and comparative studies on their performance in selenite removal and valuable SeNPs recovery. The kinetic monitoring of selenite reduction showed that the highest transformation efficiency of selenite to SeNPs was achieved at a concentration of 4.24 mM for ES129 and 4.88 mM for ES111. Ultramicroscopic analysis suggested that the SeNPs produced by ES111 and ES129 had been formed in cytoplasm and subsequently released to extracellular space through cell lysis process. Furthermore, the transcriptome analysis indicated that the expression of genes involved in bacillithiol biosynthesis, selenocompound metabolism and proline metabolism were significantly up-regulated during selenite reduction, suggesting that the transformation of selenite to Se0 may involve multiple pathways. Besides, the up-regulation of genes associated with nucleotide excision repair and antioxidation-related enzymes may enhance the tolerance of bacteria to selenite. Generally, the exploration of selenite reduction and tolerance mechanisms of the highly selenite-tolerant bacteria is of great significance for the effective utilization of microorganisms for environmental remediation.

Mechanisms of Toxicity of Heavy Metals and the Microbial Strategies for their Mitigation: A Review

Heavy metals toxicity is a major concern worldwide, especially in areas where untreated industrial effluents are released in the environment. Most important heavy metals in this context are arsenic, cadmium, chromium, copper, cobalt, lead, mercury, nickel, selenium and zinc. Some of these are also essential trace elements and play crucial roles in different biological processes. Exposure to high concentration of heavy metals is hazardous for life and can lead to various medical conditions including different types of cancers. The remediation strategies to treat these contaminants involve physical, chemical as well as biological techniques, the latter of which is considered most environment friendly and inexpensive. Bioremediation is the process of removal and detoxification of toxic pollutants using microorganisms. Many microorganisms have evolved different strategies to resist and detoxify such heavy metals. This may include excluding the metals out of the cell, binding of the metals to metal binding proteins to sequester it, conversion of metals into less or non-toxic form by enzymes and alternation of cell components to reduce metal sensitivity. Different genes and proteins are involved in these processes which can be explored for biotechnological interventions and practical applications of bioremediation. This review article discusses the mechanisms of heavy metals’ toxicity, different remediation technologies available, and the various strategies that microorganisms employ to detoxify them.

Bioremediation of Pb contaminated water using a novel Bacillus sp. strain MHSD_36 isolated from Solanum nigrum.

The Pb bioremediation mechanism of a multi-metal resistant endophytic bacteria Bacillus sp. strain MHSD_36, isolated from Solanum nigrum, was characterised. The strain tested positive for the presence of plant growth promoters such as indoleacetic acid, 1-aminocyclopropane-1-carboxylate deaminase, siderophores, and phosphate solubilization. The experimental data illustrated that exopolysaccharides and cell hydrophobicity played a role in Pb uptake. The data further showed that the cell wall biosorbed a significant amount (71%) of the total Pb (equivalent to 4 mg/L) removed from contaminated water, compared to the cell membrane (11%). As much as 11% of the Pb was recovered from the cytoplasmic fraction, demonstrating the ability of the strain to control the influx of toxic heavy metals into the cell and minimize their negative impacts. Pb biosorption was significantly influenced by the pH and the initial concentration of the toxic ions. Furthermore, the presence of siderophores and biosurfactants, when the strain was growing under Pb stress, was detected through liquid chromatography mass spectrometry. The strain demonstrated a multi-component based Pb biosorption mechanism and thus, has a great potential for application in heavy metal bioremediation.

Isolation and Electrochemical Analysis of a Facultative Anaerobic Electrogenic Strain Klebsiella sp. SQ-1.

Electricigens decompose organic matter and convert stored chemical energy into electrical energy through extracellular electron transfer. They are significant biocatalysts for microbial fuel cells with practical applications in green energy generation, effluent treatment, and bioremediation. A facultative anaerobic electrogenic strain SQ-1 is isolated from sludge in a biotechnology factory. The strain SQ-1 is a close relative of Klebsiella variicola. Multilayered biofilms form on the surface of a carbon electrode after the isolated bacteria are inoculated into a microbial fuel cell device. This strain produces high current densities of 625 μA cm-2 by using acetate as the carbon source in a three-electrode configuration. The electricity generation performance is also analyzed in a dual-chamber microbial fuel cell. It reaches a maximum power density of 560 mW m-2 when the corresponding output voltage is 0.59 V. The facultative strain SQ-1 utilizes hydrous ferric oxide as an electron acceptor to perform extracellular electricigenic respiration in anaerobic conditions. Since facultative strains possess better properties than anaerobic strains, Klebsiella sp. SQ-1 may be a promising exoelectrogenic strain for applications in microbial electrochemistry.

Exploring the Metatranscriptome of Bacterial Communities of Two Moss Species Thriving in Different Environments-Terrestrial and Aquatic.

Mosses host diverse bacterial communities essential for their fitness, nutrient acquisition, stress tolerance, and pathogen defense. Understanding the microbiome's taxonomic composition is the first step, but unraveling their functional capabilities is crucial for grasping their ecological significance. Metagenomics characterizes microbial communities by composition, while metatranscriptomics explores gene expression, providing insights into microbiome functionality beyond the structure. Here, we present for the first time a metatranscriptomic study of two moss species, Hypnum cupressiforme (Hedw.) and Platyhypnidium riparioides (Hedw.) Dixon., renowned as key biomonitors of atmospheric and water pollution. Our investigation extends beyond taxonomic profiling and offers a profound exploration of moss bacterial communities. Pseudomonadota and Actinobacteria are the dominant bacterial phyla in both moss species, but their proportions differ. In H. cupressiforme, Actinobacteria make up 62.45% and Pseudomonadota 32.48%, while in P. riparioides, Actinobacteria account for only 25.67% and Pseudomonadota 69.08%. This phylum-level contrast is reflected in genus-level differences. Our study also shows the expression of most genes related to nitrogen cycling across both microbiomes. Additionally, functional annotation highlights disparities in pathway prevalence, including carbon dioxide fixation, photosynthesis, and fatty acid biosynthesis, among others. These findings hint at potential metabolic distinctions between microbial communities associated with different moss species, influenced by their specific genotypes and habitats. The integration of metatranscriptomic data holds promise for enhancing our understanding of bryophyte-microbe partnerships, opening avenues for novel applications in conservation, bioremediation, and sustainable agriculture.

Analyzing microbial communities and metabolic functions in estuaries affected by human activity to uncover bioelectrochemical system potential

In the context of bioelectrochemical systems (BES), a profound understanding of the taxonomic composition within indigenous microbial communities is crucial. Their metabolic versatility assumes a foundational role in dictating the functionality of BES, yielding diverse applications for bioenergy production and bioremediation in anthropogenically impacted estuaries. Employing high-throughput sequencing of the V3-V4 region of 16S rRNA and predictive metagenomic analyses of three different estuaries samples (eutrophicated urban reservoir, mud volcano impacted river, and its river mouth), this study delves into the intricate interplay between these communities and their metabolic functions in response to human-induced perturbations, with a specific focus on their applicability to BES. Our findings illuminate remarkable distinctions among the three samples, manifesting in variations in microbial composition and functional metabolic pathways within the respective ecosystems. The mud volcano-affected river, characterized by the highest microbial diversity, exhibited the most diverse array of functional metabolic processes, prominently dominated by chemoheterotrophy (67.43%). In contrast, the river mouth displayed a distinct penchant for autotrophy (33.33%). The eutrophicated urban reservoir showcased a balanced coexistence of chemoheterotrophy (41.18%) and autotrophy (35.29%). Regarding metabolic potential for BES application, most of metabolism potential were associated with anodic activity, while cathodic activity was restricted to autotrophy and its relatives. The results suggested that the microbial communities anthropogenically impacted estuaries were potentially used for anodic and cathodic reactions in BES as electrogens to generate bioelectricity and reduce of pollutants.

Comparison of three unionid mussel species in removing green microalgae grown in recirculating aquaculture system effluent

Global increase in aquaculture production has created a need to reduce its environmental impacts. Nutrients could be recycled especially at land-based recirculating aquaculture systems (RAS) by cultivating green microalgae in aquaculture effluent. However, microalgae are difficult to harvest. As a multi-trophic solution, mussels could be used in harvesting microalgae. We tested three European freshwater mussels (duck mussel Anodonta anatina, swan mussel A. cygnea, and swollen river mussel Unio tumidus) for filtering two common green microalgae (Monoraphidium griffithii and Selenastrum sp.) grown in RAS effluent. Mussels decreased microalgal concentrations in the tanks 42–83% over three consecutive trials. Algal concentrations at the end of each trial were lowest for both microalgae in tanks containing Anodonta mussels. Clearance rates were higher for Anodonta mussels than for U. tumidus. Mussels biodeposited more microalgae to tank bottoms when M. griffithii was filtered. Ammonium concentration decreased or did not change in tanks with M. griffithii, but increased in tanks containing Selenastrum sp. These results suggest that of the tested species Anodonta mussels and M. griffithii show best potential for RAS effluent bioremediation application. We conclude that a co-culture of microalgae and unionid mussels could be used for recycling nutrients in aquaculture.

Methanotrophy: A Biological Method to Mitigate Global Methane Emission

Methanotrophy is a biological process that effectively reduces global methane emissions by utilizing microorganisms that can utilize methane as a source of energy under both oxic and anoxic conditions, using a variety of different electron acceptors. Methanotrophic microbes, which utilize methane as their primary source of carbon and energy, are microorganisms found in various environments, such as soil, sediments, freshwater, and marine ecosystems. These microbes play a significant role in the global carbon cycle by consuming methane, a potent greenhouse gas, and converting it into carbon dioxide, which is less harmful. However, methane is known to be the primary contributor to ozone formation and is considered a major greenhouse gas. Methane alone contributes to 30% of global warming; its emissions increased by over 32% over the last three decades and thus affect humans, animals, and vegetation adversely. There are different sources of methane emissions, like agricultural activities, wastewater management, landfills, coal mining, wetlands, and certain industrial processes. In view of the adverse effects of methane, urgent measures are required to reduce emissions. Methanotrophs have attracted attention as multifunctional bacteria with potential applications in biological methane mitigation and environmental bioremediation. Methanotrophs utilize methane as a carbon and energy source and play significant roles in biogeochemical cycles by oxidizing methane, which is coupled to the reduction of various electron acceptors. Methanotrophy, a natural process that converts methane into carbon dioxide, presents a promising solution to mitigate global methane emissions and reduce their impact on climate change. Nonetheless, additional research is necessary to enhance and expand these approaches for extensive use. In this review, we summarize the key sources of methane, mitigation strategies, microbial aspects, and the application of methanotrophs in global methane sinks with increasing anthropogenic methane emissions.