Tool For Bioremediation Research Articles

The effect of biopolymer stabilisation on biostimulated or bioaugmented mine residue for potential technosol production

Mine waste can be transformed into technosol as an ecological strategy. Despite its importance to soil functions, biological activity is often overlooked. Biopolymers can serve as innovative tools for bioremediation, facilitating chemical reactions and creating networks to encapsulate contaminants. This work aims to assess the use of bioleached and stabilised residues from a tungsten mine for technosol production. The first objective was to evaluate mine tailings for their bioleaching potential by biostimulation or bioaugmentation with strain Diaphorobacter polyhydroxybutyrativorans B2A2W2. The second was to evaluate the effect of Portland cement or biopolymers such as Carboxymethyl Cellulose (CMC) or Xanthan Gum (XG) on the stabilisation of bioleached residues. The impact of biopolymers on residues’ characteristics, such as metal leaching, number of cultivable microorganisms, compression strength and ecotoxicity was evaluated using flow systems. Over time, bioleached metallic elements decreased, except for iron (Fe). Biostimulated and stabilised residues exhibited similar trends; both CMC and cement showed low leaching rates and viable microorganisms in the same order (106 CFU × ml−1). However, bioaugmented residue stabilised with XG showed 106 CFU × ml−1 viable microorganisms and increased 2.2-fold Fe leaching than BA_Control. CMC addition to bioaugmented residue reduced 5.9-fold Fe leaching and increased 100-fold viable microorganisms. By utilising both biological and engineering approaches to characterise the technosol, this study contributes to advancing knowledge of technosol production. The residues biostimulated and stabilised with CMC produced a material useful for bio-applications, with low toxicity and metal leaching, useful for bio-applications. XG was the best stabiliser for geotechnical engineering applications, with improved compression strength. In conclusion, the study demonstrates the usefulness of biopolymer treatment for residues and emphasises the importance of selecting the appropriate biopolymer for the intended function of technosols.

Unveiling six novel bacterial strains for fipronil and thiobencarb biodegradation: efficacy, metabolic pathways, and bioaugmentation potential in paddy soil.

Soil bacteria offer a promising approach to bioremediate pesticide contamination in agricultural ecosystems. This study investigated the potential of bacteria isolated from rice paddy soil for bioremediating fipronil and thiobencarb, common agricultural pesticides. Bacterial isolates capable of degrading fipronil and thiobencarb were enriched in a mineral salt medium. A response surface methodology with a Box-Behnken design was utilized to optimize pesticide degradation with the isolated bacteria. Bioaugmentation tests were performed in paddy soils with varying conditions. Six strains, including single isolates and their mixture, efficiently degraded these pesticides at high concentrations (up to 800 µg/mL). Enterobacter sp., Brucella sp. (alone and combined), and a mixture of Stenotrophomonas sp., Bordetella sp., and Citrobacter sp. effectively degraded fipronil and thiobencarb, respectively. Notably, a single Pseudomonas sp. strain degraded a mixture of both pesticides. Optimal degradation conditions were identified as a slightly acidic pH (6-7), moderate pesticide concentrations (20-50 µg/mL), and a specific inoculum size. Bioaugmentation assays in real-world paddy soils (sterile/non-sterile, varying moisture) demonstrated that these bacteria significantly increased degradation rates (up to 14.15-fold for fipronil and 5.13-fold for thiobencarb). The study identifies these novel bacterial strains as promising tools for bioremediation and bioaugmentation strategies to tackle fipronil and thiobencarb contamination in paddy ecosystems.

Sea cucumber, Neostichopus grammatus, density and tank cleaning frequency affect abalone, Haliotis midae, growth in integrated multitrophic aquaculture

AbstractThe integrated multitrophic aquaculture (IMTA) of sea cucumber and abalone has been proposed as a potential bioremediation tool that stimulates increased abalone growth. This study assessed the role of sea cucumber stocking density and frequency of tank cleaning in IMTA on growth, water, and sludge bioremediation. The study was conducted for 16 weeks and was made of four treatments and four replicates; abalone cocultured with sea cucumber (low density—27: 1 g [abalone (ab): sea cucumber (sc)]) with tanks cleaned once a week (L1); abalone cocultured with sea cucumber (low density) with tanks cleaned twice a week (L2); abalone cocultured with sea cucumber (high density—15:1 g [ab:sc]) with tanks cleaned once a week (H1) and abalone cocultured with sea cucumber (high density) with tanks cleaned twice a week (H2). Rearing water nitrite was significantly lower (p = 0.001) at high stocking density of sea cucumbers, but sludge was unaffected. Tanks cleaned once weekly had higher sludge organic matter (p = 0.015) and sludge sulfur content (p = 0.020) and lower sludge carbon (p = 0.003) and nitrogen content (p = 0.049). At the end of the experiment, the stocking density of sea cucumber and frequency of tank cleaning affected abalone mean weight [p = 0.047; p = 0.011, respectively] without a significant interaction (p = 0.517). Abalone in H1 had a higher mean weight and shell length than abalone in L2 and H2 but was similar to those in L1. The stocking density and frequency of cleaning used in this study had no effect on the growth of sea cucumbers [p = 0.150; p = 0.470, respectively]. This study has shown that in an abalone–sea cucumber IMTA system, the stocking density of sea cucumber and the frequency at which tanks are cleaned influence abalone growth and bioremediation of the rearing water. Our result suggests H1 as the best density (ab:sc) and cleaning frequency. The tank cleaning frequency alone affects the tank sludge quality; tanks need not be washed too frequently as, in addition to causing animal stress, cleaning markedly increased carbon and nitrogen level of tank sludge. Both these effects are likely to negatively impact abalone growth.

Mechanisms of efficient polyacrylamide degradation: From multi-omics analysis to structural characterization of two amidohydrolases

Polyacrylamide (PAM) is a high molecular weight polymer with extensive applications. However, inefficient natural degradation of PAM results in its environmental accumulation. Here, using multi-omics analysis, we constructed the PAM biodegradation pathway in Klebsiella sp. PCX, an efficient PAM-degrading bacterium. Subsequently, two unclassified amidohydrolases (PCX00451 and PCX04581) were identified as key factors for rapid PAM biodegradation, both of which possessed much higher hydrolysis efficiency for PAM than for small molecule amide compounds. Besides, crystal structures of PCX00451 and PCX04581 were solved. Both two amidohydrolases were consisted with a twisted triosephosphateisomerase (TIM)-barrel and a smaller β-sandwich domain. And their binding pockets were in the conserved metal center of TIM-barrel domain. Moreover, Asp267 of PCX00451 and Asp282 of PCX04581 were examined as active sites for acid/base catalysis. Our research characterized the molecular mechanisms of two efficient amidohydrolases, providing theoretical basis and valuable tools for PAM bioremediation.

Development and performance of microalgae-based symbiotic systems for high-strength chemical oxygen demand wastewater treatment from the sugar mills

Agricultural and agro-industrial activities have risen exponentially to meet the ever-growing demand for food, energy, and other important resources. High freshwater consumption occurs in these sectors and is discharged as effluent containing excessive organic loads that require treatment. In this study, microalgal, bacterial, and fungal (yeast) isolates native to the sugar industry effluent were screened for effective chemical oxygen demand (COD) removal from wastewater when co-cultured. The microalgae-bacteria consortium (MBC) comprised Chlorella sorokiniana A7 and three bacterial strains including Rhodococcus sp. B009, Bacillus sp. B010, and B013; whilst the microalgae-yeast consortium (MYC) consisted of Chlorella sorokiniana A7 and Saccharomyces cerevisiae Y2. When the Chlorella sorokiniana-based symbiotic systems were characterized in sugar industry wastewater, excellent COD removal efficiencies were achieved compared to the axenic Chlorella sorokiniana A7. The COD removal efficiencies were 86 %, and 71 % after 96 h of cultivation for MBC, and MYC, respectively. After 168 h of cultivation in wastewater, ≥90 % of COD removal efficiency was observed in both MBC and MYC systems. The MYC also showed improved chlorophyll-a content, photosynthesis, and respiration in Chlorella sorokiniana A7. This study has demonstrated the efficiency of Chlorella sorokiniana-based consortium systems that could be used as eco-friendly and sustainable bioremediation tools for high-strength COD wastewater streams. An insight into mechanisms of interactions between Chlorella sp., and co-cultured microbial strains grown in sugar industry wastewater still needs further studies.

Optimization of strontium removal by Tetraselmis chui grown in bubble column photobioreactors

Green microalgae of the class Chlorodendrophyceae have recently attracted the interest of researchers due to their ability to form micropearls (intracellular inclusions of amorphous calcium carbonate) highly enriched in Sr. The marine species Tetraselmis chui (included in the class Chlorodendrophyceae) shows high uptake of both stable and radioactive Sr isotopes and has been suggested as a potential candidate for the development of new bioremediation tools regarding radioactive 90Sr pollution. In this study, we optimized Sr removal from seawater by growing T. chui in 1-L bubble column photobioreactors (PBRs) with and without CO2 supply. Culturing T. chui in bubble column PBRs greatly improves cell production and Sr removal compared to previous studies. Furthermore, the addition of 10 mL L−1 h−1 CO2 further accelerates T. chui growth and results in better Sr removal rates. This study presents promising results for the development of new bioremediation methods to treat 90Sr pollution.

The seaweed Chaetomorpha linum cultivated in an integrated multitrophic aquaculture system: A new tool for microplastic bioremediation?

Microplastics (MPs) are emerging pollutants with detrimental impacts on ecosystems and human health. Due to their adverse effects, new strategies to mitigate MP pollution in the marine environment need to be developed urgently. In this context, the capability of the seaweed Chaetomorpha linum (Chlorophyta, Cladophorales) to trap MPs, as well as the effectiveness of a simple washing procedure to clean up the harvested seaweed biomass, were investigated. This algal species was grown in an integrated multitrophic aquaculture system (IMTA), where bioremediator organisms such as macroalgae, polychaetes, sponges and mussels were farmed in the vicinity of the fish cages. MPs trapped in C. linum were classified based on shape and size, and representative samples of each shape were analysed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to evaluate their chemical composition. Fibre MPs were the most abundant (97.3 %), while the size ranged from 0.025 to 2.00 mm, with most samples being in the size range 0.80–1.00 mm. MPs were composed mainly of polypropylene, polystyrene, and polyethylene. They were efficiently removed from the cultured seaweeds by a simple density separation procedure, consisting of three extractions with hypersaline solutions of sodium chloride. These results suggest that C. linum cultivated in an IMTA system can be proposed as a bioremediator to capture MPs from the surrounding environment. At the same time, harvested and cleaned green seaweeds may be considered a co-product of the bioremediation process and can find application in several biotechnological fields, including the use as a food source for human consumption.

Structural and Mechanistic Insights into a Novel Monooxygenase for Poly(acrylic acid) Biodegradation.

Polyacrylamide (PAM) is a high-molecular-weight polymer with extensive applications. However, the inefficient natural degradation of PAM results in environmental accumulation of the polymer. Biodegradation is an environmentally friendly approach in the field of PAM treatment. The first phase of PAM biodegradation is the deamination of PAM, forming the product poly(acrylic acid) (PAA). The second phase of PAM biodegradation involves the cleavage of PAA into small molecules, which is a crucial step in the degradation pathway of PAM. However, the enzyme that catalyzes the degradation of PAA and the molecular mechanism remain unclear. Here, a novel monooxygenase PCX02514 is identified as the key enzyme for PAA degradation. Through biochemical experiments, the monooxygenase PCX02514 oxidizes PAA with the participation of NADPH, causing the cleavage of carbon chains and a decrease in the molecular weight of PAA. In addition, the crystal structure of the monooxygenase PCX02514 is solved at a resolution of 1.97 Å. The active pocket is in a long cavity that extends from the C-terminus of the TIM barrel to the protein surface and exhibits positive electrostatic potential, thereby causing the migration of oxygen-negative ions into the active pocket and facilitating the reaction between the substrates and monooxygenase PCX02514. Moreover, Arg10-Arg125-Ser186-Arg187-His253 are proposed as potential active sites in monooxygenase PCX02514. Our research characterizes the molecular mechanism of this monooxygenase, providing a theoretical basis and valuable tools for PAM bioremediation.

Microbial Immobilized Enzyme Biocatalysts for Multipollutant Mitigation: Harnessing Nature's Toolkit for Environmental Sustainability.

The ever-increasing presence of micropollutants necessitates the development of environmentally friendly bioremediation strategies. Inspired by the remarkable versatility and potent catalytic activities of microbial enzymes, researchers are exploring their application as biocatalysts for innovative environmental cleanup solutions. Microbial enzymes offer remarkable substrate specificity, biodegradability, and the capacity to degrade a wide array of pollutants, positioning them as powerful tools for bioremediation. However, practical applications are often hindered by limitations in enzyme stability and reusability. Enzyme immobilization techniques have emerged as transformative strategies, enhancing enzyme stability and reusability by anchoring them onto inert or activated supports. These improvements lead to more efficient pollutant degradation and cost-effective bioremediation processes. This review delves into the diverse immobilization methods, showcasing their success in degrading various environmental pollutants, including pharmaceuticals, dyes, pesticides, microplastics, and industrial chemicals. By highlighting the transformative potential of microbial immobilized enzyme biocatalysts, this review underscores their significance in achieving a cleaner and more sustainable future through the mitigation of micropollutant contamination. Additionally, future research directions in areas such as enzyme engineering and machine learning hold immense promise for further broadening the capabilities and optimizing the applications of immobilized enzymes in environmental cleanup.

Bacillus subtilis as an effective tool for bioremediation of lead, copper and cadmium in water

Bioremediation is a promising technique for the removal and recovery of contaminated areas, which is based on the ability of organisms to convert toxic substances into less harmful or inert compounds. Here, we evaluate the capacity of the Bacillus subtilis (BS) bacteria to bioadsorved heavy metals such as lead (Pb), copper (Cu) and cadmium (Cd) in water samples. Water samples were laboratory contaminated Pb at 500 ppm, Cu and Cd at 100 ppm. First, the growth curve of BS was plotted using Tryptone Soy Broth (TSB) at 100% (TSB100) and 33% (TSB33). Later, BS was studied in water containing all three metals separately and simultaneously. All solutions were stirred at 150 rpm, 35 ℃ for periods that ranged from 1 to 144 h. The heavy metal analyses were performed by X-ray fluorescence and Inductively Coupled Plasma Mass Spectrometry. The results showed that BS was resistant to Cu, Cd and Pb in water, with active multiplication and reduction in the concentration of the metals. The highest removal efficiency, in the presence of each heavy metal, reached 100% with Pb, 92.3% with Cd and 89% with Cu. In the solution with the mixture of heavy metals, Cd and Pb levels reduced significantly. However, the mixture of metals negatively affected the removal of Cu. In conclusion, the implement using Bacillus-type bacteria can be efficient in the biosorption of heavy metals from aqueous solutions and can be employed as a cost-effective treatment for the bioremediation of industrial effluents and contaminated areas.

Indigenous alkaliphiles as an effective tool for bioremediation of bauxite residue (red mud)

The microorganisms thriving in ageing Bauxite residue, or red mud, have captured scientific interest for their adaptability to extreme conditions. This study investigates extremophilic microbial communities present in Indian red mud for their potential to neutralize the residue and extracting metals. These communities thrive in the highly alkaline, sodic, and metal-rich conditions of this challenging environment. The research specifically highlights alkali-halophilic species and their ability to withstand pH fluctuations (7–11) and varying NaCl levels (0–3 M). Out of the 13 isolates analyzed, all preferred a pH range of 9–10 and tolerated NaCl up to 1.5–2 M. Notably, Evansella cellulosilytica and Halalkalibacterium halodurans, showed superior tolerance index for Al3+ and Cr6+ at 2000 ppm, as well as Co2+ at 1000 ppm, followed by Sutcliffiella cohnii. However, the tolerance index for Cu2+, Te4+, and Hg2+ was relatively low for all tested strains. Additionally, Alkalihalobacillus sp. demonstrated remarkable tolerance to 10% red mud, facilitated by the production of mixed acids, neutralizing the pH within 24 h. The study proposes a potential mechanism for metal and red mud tolerance through genomic analysis using Rapid Annotation Subsystem Technology (RAST), revealing stress tolerance mechanisms, metal resistance genes, ion transporters, hydrolytic enzymes, siderophore production, and organic acid synthesis. Indigenous species like E. cellulosilytica, H. halodurans, S. cohnii, and Alkalihalobacillus sp. emerge as promising candidates for red mud bioremediation, providing insights into sustainable strategies for red mud disposal.

Genome sequencing, annotation and application of a strain of Microbacterium paraoxydans – A bacterium with arsenic bioremediation and plant growth promoting potential

A heavy metal hypertolerant plant growth-promoting bacterium was isolated from the arsenic-contaminated garden soil of Bhagobangola I block (Murshidabad district). Metagenomic classification identified the bacterial isolate as a member of the genus Microbacterium. Taxonomic assessment of the isolated strain revealed its maximum average nucleotide identity (89.99 %) with the Microbacterium paraoxydans strain DSM 15019. Prokaryotic genome annotation was performed by Prokka, DFAST and RAST. The entire genome consisted of 3365911 bases with 69.90 % GC content. Prokka detected 3216 coding sequences (1461 hypothetical sequences), 3283 genes, 10 miscellaneous RNAs, 3 rRNAs, 53 tRNAs and 1 tmRNA in the bacterial genome. DFAST detected 3257 coding sequences (1217 hypothetical sequences), 3 rRNA sequences and 53 tRNA sequences in the bacterial genome. RAST detected 3285 coding sequences and 49 RNAs in the genome. Only 25 % of these coding sequences could be categorised in the RAST subsystems. In RAST, 789 and 32 coding sequences were considered as non-hypothetical and hypothetical, respectively. The genes and gene clusters responsible for arsenic resistance (arsR, arsB, arsC, acr1, acr2 and acr3), tolerance to other heavy metals (copper, manganese, zinc, etc.) and plant growth promotion (auxin biosynthesis, siderophore-mediated iron acquisition, phosphate and polyphosphate metabolism, trehalose biosynthesis, etc.) were also identified in the Microbacterium paraoxydans genome. The bioremediation potential and plant growth-promoting nature of the bacterium were confirmed by silver diethyl dithio carbamate (SDDC) method and pot experiments, respectively. The aforementioned traits point towards potential of the bacterium as a bioremediation tool and biofertilizer for reducing arsenic toxicity and promoting plant growth.

The Microalgae Chlamydomonas for Bioremediation and Bioproduct Production.

The extensive metabolic diversity of microalgae, coupled with their rapid growth rates and cost-effective production, position these organisms as highly promising resources for a wide range of biotechnological applications. These characteristics allow microalgae to address crucial needs in the agricultural, medical, and industrial sectors. Microalgae are proving to be valuable in various fields, including the remediation of diverse wastewater types, the production of biofuels and biofertilizers, and the extraction of various products from their biomass. For decades, the microalga Chlamydomonas has been widely used as a fundamental research model organism in various areas such as photosynthesis, respiration, sulfur and phosphorus metabolism, nitrogen metabolism, and flagella synthesis, among others. However, in recent years, the potential of Chlamydomonas as a biotechnological tool for bioremediation, biofertilization, biomass, and bioproducts production has been increasingly recognized. Bioremediation of wastewater using Chlamydomonas presents significant potential for sustainable reduction in contaminants and facilitates resource recovery and valorization of microalgal biomass, offering important economic benefits. Chlamydomonas has also established itself as a platform for the production of a wide variety of biotechnologically interesting products, such as different types of biofuels, and high-value-added products. The aim of this review is to achieve a comprehensive understanding of the potential of Chlamydomonas in these aspects, and to explore their interrelationship, which would offer significant environmental and biotechnological advantages.

Biodegradation of sodium lauryl ether sulfate (SLES) contamination by Pseudomonas aeruginosa isolates

Sodium lauryl ether sulfate (SLES) is a surfactant commonly used in the formulation of detergents, which is typically disposed of in wastewater treatment plants. The current study describes the effectiveness of bacteria isolated from Iraqi wastewater to remove SLES. 16S rRNA genetic analysis revealed that this strain is Pseudomonas aeruginosa. Three temperatures (30, 35, and 40oC) and pH values (5,7, and 9) were chosen for this study, and three concentrations of SLES (25, 50, and 100 mg/L) were used. The SLES anionic surfactant showed that the best biodegradation by Pseudomonas aeruginosa was at a temperature of 30oC and both pH 7 and 9, while the removal percentages for them were 98.44% and 96.36%, respectively, at 25 mg/L of SLES. The outcomes of this study revealed the potential and significance of SLES removal in actual effluents by aerobic biodegradation. The ability of this bacterium to degrade SLES makes the bacterium an important tool for bioremediation.

Isolation of biocrust cyanobacteria and evaluation of Cu, Pb, and Zn immobilisation potential for soil restoration and sustainable agriculture

Soil contamination by heavy metals represents an important environmental and public health problem of global concern. Biocrust-forming cyanobacteria offer promise for heavy metal immobilisation in contaminated soils due to their unique characteristics, including their ability to grow in contaminated soils and produce exopolysaccharides (EPS). However, limited research has analysed the representativeness of cyanobacteria in metal-contaminated soils. Additionally, there is a lack of studies examining how cyanobacteria adaptation to specific environments can impact their metal-binding capacity. To address this research gap, we conducted a study analysing the bacterial communities of cyanobacteria-dominated biocrusts in a contaminated area from South Sardinia (Italy). Additionally, by using two distinct approaches, we isolated three Nostoc commune strains from cyanobacteria-dominated biocrust and we also evaluated their potential to immobilise heavy metals. The first isolation method involved acclimatizing biocrust samples in liquid medium while, in the second method, biocrust samples were directly seeded onto agar plates. The microbial community analysis revealed Cyanobacteria, Bacteroidota, Proteobacteria, and Actinobacteria as the predominant groups, with cyanobacteria representing between 13.3 % and 26.0 % of the total community. Despite belonging to the same species, these strains exhibited different growth rates (1.1–2.2 g L−1 of biomass) and capacities for EPS production (400–1786 mg L−1). The three strains demonstrated a notable ability for metal immobilisation, removing up to 88.9 % of Cu, 86.2 % of Pb, and 45.3 % of Zn from liquid medium. Cyanobacteria EPS production showed a strong correlation with the removal of Cu, indicating its role in facilitating metal immobilisation. Furthermore, differences in Pb immobilisation (40–86.2 %) suggest possible environmental adaptation mechanisms of the strains. This study highlights the promising application of N. commune strains for metal immobilisation in soils, offering a potential bioremediation tool to combat the adverse effects of soil contamination and promote environmental sustainability.

Chitinases: expanding the boundaries of knowledge beyond routinized chitin degradation.

Chitinases, enzymes that degrade chitin, have long been studied for their role in various biological processes. They play crucial roles in the moulting process of invertebrates, the digestion of chitinous food, and defense against chitin-bearing pathogens. Additionally, chitinases are involved in physiological functions in crustaceans, such as chitinous food digestion, moulting, and stress response. Moreover, chitinases are universally distributed in organisms from viruses to mammals and have diverse functions including tissue degradation and remodeling, nutrition uptake, pathogen invasion, and immune response regulation. The discovery of these diverse functions expands our understanding of the biological significance and potential applications of chitinases. However, recent research has shown that chitinases possess several other functions beyond just chitin degradation. Their potential as biopesticides, therapeutic agents, and tools for bioremediation underscores their significance in addressing global challenges. More importantly, we noted that they may be applied as bioweapons if ethical regulations regarding production, engineering and application are overlooked.

Evaluation of antibiofilm activity of metal oxides nanoparticles and carbon nanotubes coated styrofoam on the bacterium Jeotgalicoccus huakuii

The co-existence of metal oxide nanoparticles (MONPs), carbon-based nanomaterials and microplastics (MPs) in the natural environment are expected to be of growing global concern due to their increasing abundance and persistence in the environment worldwide. Knowledge of the interaction of the above compounds particularly under light irradiation in water remains limited. In the present study, the possible individual and combined toxic effects of MONPs, carbon nanotubes (CNTs) through styrofoam (SF) on the environmental bacterium Jeotaglicoccus huakuii were systematically investigated. The fabricated MONPs and CNTs were characterized using the following techniques: FT-IR (functional groups), XRD (crystallinity), SEM, and EDX (topological morphology). The objective of this study was to investigate and identify naturally occurring bacteria capable of mitigating and detoxifying toxic pollutants under adverse conditions. Moreover, the assessment of minimum inhibitory concentration (MIC) was made through an agar well plate method, resazurin (ELISA measurement), growth kinetics and bacterial viability were assessed employing live and dead assay and biofilm combating ability was analyzed using an antibiofilm assay. Further, the biotransformation of f-MWCNTs by J. huakuii was evaluated employing RT-PCR and SEM analysis. The results demonstrated that the toxicity of Pb3O4@f-MWCNTs was comparatively higher than the remaining Pb3O4 NPs and SF coated NPs.. Interestingly, J. huakuii showed resistance against f-MWCNTs at very high concentrations and able to utilize f-MWCNTs as a sole carbon source suggesting J. huakuii as a suitable aquatic bioremediation tool for both MONPs and CNTs transfer via MPs. The results also enhanced our understanding of the affinity of MPs towards MONPs and CNTs under extreme environmental conditions.

Identification and characterization of a promiscuous metallohydrolase in metallo-β-lactamase superfamily from a locally isolated organophosphate-degrading Bacillus sp. strain S3wahi

In this present study, characteristics and structure-function relationship of an organophosphate-degrading enzyme from Bacillus sp. S3wahi were described. S3wahi metallohydrolase, designated as S3wahi-MH (probable metallohydrolase YqjP), featured the conserved αβ/βα metallo-β-lactamase-fold (MBL-fold) domain and a zinc bimetal at its catalytic site. The metal binding site of S3wahi-MH also preserves the H-X-H-X-D-H motif, consisting of specific amino acids at Zn1 (Asp69, His70, Asp182, and His230) and Zn2 (His65, His67, and His137). The multifunctionality of S3wahi-MH was demonstrated through a steady-state kinetic study, revealing its highest binding affinity (KM) and catalytic efficiency (kcat/KM) for OP compound, paraoxon, with values of 8.09 × 10−6 M and 4.94 × 105 M−1 s−1, respectively. Using OP compound, paraoxon, as S3wahi-MH native substrate, S3wahi-MH exhibited remarkable stability over a broad temperature range, 20 °C – 60 °C and a broad pH tolerance, pH 6–10. Corresponded to S3wahi-MH thermal stability characterization, the estimated melting temperature (Tm) was found to be 72.12 °C. S3wahi-MH was also characterized with optimum catalytic activity at 30 °C and pH 8. Additionally, the activity of purified S3wahi-MH was greatly enhanced in the presence of 1 mM and 5 mM of manganese (Mn2+), showing relative activities of 1323.68 % and 2073.68 %, respectively. The activity of S3wahi-MH was also enhanced in the presence of DMSO and DMF, showing relative activities of 270.37 % and 307.41 %, respectively. The purified S3wahi-MH retained >60 % residual activity after exposure to non-ionic Tween series surfactants. Nevertheless, the catalytic activity of S3wahi-MH was severely impacted by the treatment of SDS, even at low concentrations. Considering its enzymatic properties and promiscuity, S3wahi-MH emerges as a promising candidate as a bioremediation tool in wide industrial applications, including agriculture industry.

Bioremediation potential of Bacillus sp. and Paenebacillus sp. novel lead-resistant isolates: Identification, characterization, and optimization studies

Environmental pollution by heavy metals and other toxic substances has increasingly become a global health concern. Lead is a hazardous environmental contaminant that is been released to the surface causing deleterious health effects to man. Various strategies have been employed such as excavation, precipitation, and vitrification to remove lead from polluted sites. However, bioremediation of heavy metal contaminated sites has served as a cost-effective and ecofriendly tool for detoxifying and restoration of ecological entities. In this study, we reported the isolation and optimization of two novel lead-resistant isolates from active goldmine contaminated site of Anka, Zamfara state Nigeria. Results of Atomic Absorption Spectroscopy (AAS) showed higher lead concentration from the sampled sites (p<0.05) than the USEPA standard (400 mg/Kg). Paenebacillus sp. strain BUK_BCH_BTE 3 (MT160418) and Bacillus sp. strain BUK_BCH_BTE 4 (MT160452) were identified based on the 16 S rRNA partial gene sequencing of the locally isolated microorganisms. Characterization of the two isolates revealed optimum growth at 37 °C, a pH of 7.0 over 48 hrs while utilizing inoculum volumes of 100 µL each. The two isolates utilized optimum sucrose concentrations at 10–20 g/L, while 5 g/L nitrogen source and 5 g/L of urea were optimum for Paenebacillus sp. as well as Bacillus sp. respectively. An optimal lead concentration of 1000 g/L was obtained by both isolates. Furthermore, the two isolates tolerated up to 3000 mg/L lead nitrate. Mercury, a toxic heavy metal, was noticed to hinder the growth of both isolates significantly at p<0.05. Hence, the locally isolated Paenebacillus sp. and Bacillus sp. could be used as promising tools for bioremediation of lead-contaminated environment.

Neonicotinoid Effects on Soil Microorganisms: Responses and Mitigation Strategies

Pesticides play a critical role in pest management and agricultural productivity; however, their misuse or overuse can lead to adverse effects on human health and the environment, including impacts on ecosystems and contamination. Currently, neonicotinoids (NNIs) are the most widely used systemic insecticides and are questioned worldwide for their possible impacts on pollinators. After NNI application, a substantial portion is not absorbed by the plant and may accumulate in the soil, affecting the soil microbial community. In this review, we explore the main studies carried out either in the laboratory or in the field about this matter. The studies report that the application of NNIs affects soil microbial activity and can act on microbial communities differently due to their unique chemical properties, degradation in soil, soil type, effects on soil properties, and methods of application. NNIs alter the diversity, structure, and abundance of soil microbes, in some cases increasing or decreasing their representativeness in soil. Bacterial phyla like Pseudomonadota, Bacillota, Actinomycetota, and Nitrospirota increase after NNI exposure, just like the families Nitrosomonadaceae, Nitrososphaeraceae, Nitrospiraceae, Sphingomonadaceae, Streptomycetaceae, and Catenulisporaceae. At the bacterial genus level, Nitrospira was associated with a decrease in nitrification processes in soil. The bacterial genera Sphingomonas, Streptomyces, Catenulispora, Brevundimonas, Pedobacter, and Hydrogenophaga are related to NNI degradation after application. Microorganisms could minimize the impacts of NNIs in agricultural soil. Therefore, the use of bioinoculation as a bioremediation tool is explored as an alternative to contribute to agricultural sustainability.