Immobilization Matrix Research Articles

Pyrite functionalized Black Soldier Fly feces biochar for mine soil quality improvement and heavy metals immobilization

Frequent mining activities have led to an increasing transfer of heavy metals to the soil. Pyrite functionalized Black Soldier Fly feces biochar composite material (BFFS) was synthesized to immobilize Cu and Pb in contaminated mine soil and improve soil quality in our study. Incubation experiments showed that BFFS significantly reduced the leaching rates by 96 % and 90 % for Cu and Pb, respectively, when compared to the control after 220 days. Speciation transformation analysis further revealed that BFFS could significantly reduce easily labile fractions of Cu and Pb, and transformed to recalcitrant fractions. Moreover, BFFS significantly improved the quality of mine soil combined with soil quality index analysis. The potential toxicity and bioavailability of Cu and Pb can still be effectively reduced by BFFS, even during a 90-day field experiment. In addition, the mine soil improved by BFFS further promoted the survival and growth of ramie. Multiple characterization analyses and related experiments indicated that ion exchange, adsorption, complexation, and coprecipitation mainly contribute to the high efficiency immobilization of Cu and Pb by BFFS. These findings could bring some fresh perspectives on the development of immobilization materials and related technologies for the economical, green and sustainable remediation of heavy metals contaminated mine soil.

Improved performance and mechanism of the long-term vanadium(V) remediation by immobilization of rice washing waste

There is an urgent need to develop more efficient microbial technologies suitable for vanadium (V) stressed environments. In this study, rice washing waste (RWW) was utilized as both the carbon and microbial sources immobilized together with sludge to treat V-containing wastewater. Continuous flow reactors were operated, and V(V) removal efficiencies (30 d) with polyvinyl alcohol (PVA) and chitosan as embedded carriers achieved 9.0% and 79.4%, respectively. A superior V(V) removal performance (91.45%) was achieved in the continuous flow reactors with chitosan-based immobilized materials (70 d). V was detected on the surface and within the material, and V(IV) was found, indicating that both adsorption and microbes were able to contribute to V(V) remediation. Increase in the fractions of some functional microbes were observed in response to V(V) stress (unclassified_f_Comamonadaceae, unclassified_f_Enterobacteriaceae) and ammonia stress (unclassified_f_Hungateiclostridiacea). RWW could serve as suitable carbon and microbial sources for long-term operation and enhance V(V) removal by immobilized together with sludge, thereby unveiling a new method for both food and V contaminants.

Enhancement in Formation of Insoluble Arsenic Phases without Re-Leaching by Particle Size of Excavated Sediment with Iron Sulfate Heptahydrate

ABSTRACT Massive quantities of naturally arsenic-containing sediments are excavated for construction. Chemical immobilization is applied to such excavated materials for reuse. Appropriate physicochemical properties should be understood to enhance the formation of the insoluble arsenic phases without re-leaching. The up-flow column retention test flowing 10 mg L−1 of arsenic solution was conducted to understand how the retention of arsenic and the phases of arsenic immobilized by iron sulfate heptahydrate depend on the particle size of the excavated sediment. The amount of arsenic retained on the immobilization material (particle size of 0.5 mm) during the retention test was lower for the larger particle size of the excavated sediment. However, arsenic was more stably retained on the immobilization material for the large particle sizes (1.0–2.0 and 2.0–5.0 mm) and the amount of arsenic re-leached was 12% of that in the small one (<0.5 mm). The percentages of arsenic in fraction 3 of sequential extraction increased from 45% to 68% with increasing the particle size. These results indicate that the excavated sediment with a larger particle size than that of immobilization material retains less arsenic on the immobilization material, but the arsenic phases immobilized are more stable, resulting in less arsenic re-leaching. This study suggests that the use of excavated sediment with a particle size larger than that of the immobilization material is desirable for the application of immobilization technique without re-leaching.

Virtual Screening and Validation of Affinity DNA Functional Ligands for IgG Fc Segment.

The effective attachment of antibodies to the immune sensing interface is a crucial factor that determines the detection performance of immunosensors. Therefore, this study aims to investigate a novel antibody immobilization material with low molecular weight, high stability, and excellent directional immobilization effect. In this study, we employed molecular docking technology based on the ZDOCK algorithm to virtually screen DNA functional ligands (DNAFL) for the Fc segment of antibodies. Through a comprehensive analysis of the key binding sites and contact propensities at the interface between DNAFL and IgG antibody, we have gained valuable insights into the affinity relationship, as well as the principles governing amino acid and nucleotide interactions at this interface. Furthermore, molecular affinity experiments and competitive binding experiments were conducted to validate both the binding ability of DNAFL to IgG antibody and its actual binding site. Through affinity experiments using multi-base sequences, we identified bases that significantly influence antibody-DNAFL binding and successfully obtained DNAFL with an enhanced affinity towards the IgG Fc segment. These findings provide a theoretical foundation for the targeted design of higher-affinity DNAFLs while also presenting a new technical approach for immunosensor preparation with potential applications in biodetection.

Synthesis and comparison of the performance of two different water-soluble phthalocyanine based electrochemical biosensor

Herein, a comparative study between novel water-soluble phthalocyanine-based biosensors was performed for the application of glucose sensing. For this purpose, two different copper (II) and manganese (III) phthalocyanines and their water-soluble derivatives were synthesized, and then their role as a supporting material for enzyme immobilization was evaluated by comparing their sensor performances. Two different phthalocyanine (AP-OH2-MnQ (MnPc) and AP-OH2-CuQ (CuPc)) were tested using electrochemical biosensor with immobilized glucose oxidase (GOx). To the best of our knowledge, the related water-soluble phthalocyanine-based glucose biosensors were attempted for the first time, and the developed approach resulted in improved biosensor characteristics. The constructed biosensors GE/MnPc/GOx and GE/CuPc/GOx showed good linearity between 0.003–1.0 mM and 0.05–0.4 mM, respectively. The limit of detection was estimated at 0.0026 mM for the GE/MnPc/GOx and 0.019 mM for the GE/CuPc/GOx. KMapp and sensitivity values were also calculated as 0.026 mM and 175.043 µAmM−1 cm−2 for the GE/MnPc/GOx biosensor and 0.178 mM and 117.478 µAmM−1 cm−2 for the GE/CuPc/GOx biosensor. Moreover, the fabricated biosensors were successfully tested to detect glucose levels in beverages with high recovery results. The present study shows that the proposed water-soluble phthalocyanines could be a good alternative for quick and cheap glucose sensing with improved analytical characteristics.

Rederiving kinetics to model biohydrogen production from immobilized microalgae alginate beads at various polymerization degrees of alginate under dark fermentative environment

The performance of immobilized microalgae-alginate beads on biohydrogen production and its stability across several dark fermentation cycles is influenced by the sodium alginate concentrations. Thus, it is vital to determine the optimal condition for immobilization to achieve maximum encapsulation efficiency, stability and biohydrogen production. In this work, different sodium alginate concentrations (2 to 8 w/v%) were used to immobilize microalgae in influencing the dark fermentative biohydrogen productions from municipal wastewater, and its reusability was also investigated. The immobilized microalgae-alginate beads with sodium alginate concentration of 2 % showed the lowest stability and biohydrogen production in all cycles. The highest biohydrogen production was achieved by immobilized microalgal-alginate beads prepared from 8 % sodium alginate, followed by 6 % and 4 % in the first and second cycles. However, 8 % of immobilized microalgae-alginate beads generated the lowest biohydrogen volume during the third cycle. Besides, a model was rederived from the modified Gompertz model and Fick's law of diffusion equation to describe the relationship between polymeric viscosity and biohydrogen production from immobilized microalgae-alginate beads with different sodium alginate concentrations. As the sodium alginate concentrations increased, the viscosity also increased which significantly affected the properties of immobilization matrix formed such as encapsulation efficiency, growth of microalgae, diffusion of substrate and biohydrogen yield. The rederived model managed to fit the experimental data with a coefficient of determination values of >0.95 for all the polymerization degrees of alginate. The kinetic parameters, namely, yield of biohydrogen and specific microalgae growth rate of sodium alginate concentration of 6 % were 129.80 L kg−1 and 4.69 h−1, respectively, which were considered as maximum results as compared with other sodium alginate concentrations. Besides, the difference in biohydrogen productions for all cycles and kinetic data of biohydrogen yields obtained from the rederived model between sodium alginate concentration of 6 % and 8 % only exhibited a slight variance (<3 %). Thus, sodium alginate concentration of 6 % was considered to be an optimal for immobilizing microalgae in performing the dark fermentation. Overall, the results revealed the significance of suitable sodium alginate concentration in maximizing the immobilization of microalgae for performing the dark fermentative biohydrogen production.

Cleaning and Durability of Upper Extremity Orthotics: A Patient's Perspective.

Introduction We aimed to evaluate orthotic hygiene, preference for immobilization material, and frequency of unplanned orthotic adjustments and replacements. Methods All patients with fiberglass casts, thermoplastic splints, or prefabricated braces who presented at a large private academic institution between January 2020 and July 2023 were provided an 11-item survey assessing the length of immobilization, frequency of orthotic changes, orthotic hygiene, preference of immobilization, and whether patients recall instructions regarding orthotic care. Results A total of 385 surveys were collected, consisting of 96 (24.9%) casts, 202 (52.5%) thermoplastic splints, and 87 (22.6%) prefabricated braces. Patients were most frequently immobilized for two to six weeks. Of those, 106 (27.5%) patients required an unplanned adjustment or replacement. Almost half (182 patients, 47.3%) attempted to clean their orthotics, which was significantly greater among thermoplastic splints. A total of 229 (59.5%) respondents reported either not receiving or were unsure if they received instruction on proper orthotic hygiene. Conclusion Orthotic care and hygiene instructions are often overlooked or not retained by patients. Nearly one-third of patients required an unplanned adjustment or replacement, which was most frequent with thermoplastic orthotics.

Boosting catalytic efficiency of lipase by regulating amphiphilic microenvironment through reversible addition-fragmentation chain transfer polymerized modifications on polyacrylonitrile fiber

Lipases are increasingly attracting attention in green and sustainable biodiesel production. Currently, the research emphasis lies in immobilizing unstable lipase onto carriers to enhance its performance. Polyacrylonitrile fiber (PANF) is considered to be a promising material for lipase immobilization due to its excellent properties. In this study, functional carriers with regulated surface hydrophobicity were obtained by loading functional groups on PANF via reversible addition-fragmentation chain transfer (RAFT) polymerized modification, and Candida rugosa lipase (CRL) was covalently immobilized on the carrier with glutaraldehyde as a linker. By employing this optimized biocatalyst PANF@BMA&2VImBr-NH2-CRL in the transesterification process, the yield of biodiesel derived from soybean oil reached an impressive 92.7 %. The outstanding performance can be attributed to the activation of lipase interface induced by hydrophobic microenvironment derived from alkyl ester on the carrier skeleton. Moreover, the stability and storage performance of immobilized lipase were significantly improved. The immobilized lipase exhibited facile recovery and maintained a consistent biodiesel yield of 80.9 % even after undergoing 5 cycles of reuse, thereby highlighting its potential for sustainable production. To sum up, our research demonstrates that the designed and prepared process of PANF-supported lipase offers a promising approach for enzyme immobilization, thereby presenting extensive potential applications in the field of biotechnology.

Allergen Microarrays and New Physical Approaches to More Sensitive and Specific Detection of Allergen-Specific Antibodies.

The prevalence of allergic diseases has increased tremendously in recent decades, which can be attributed to growing exposure to environmental triggers, changes in dietary habits, comorbidity, and the increased use of medications. In this context, the multiplexed diagnosis of sensitization to various allergens and the monitoring of the effectiveness of treatments for allergic diseases become particularly urgent issues. The detection of allergen-specific antibodies, in particular, sIgE and sIgG, is a modern alternative to skin tests due to the safety and efficiency of this method. The use of allergen microarrays to detect tens to hundreds of allergen-specific antibodies in less than 0.1 mL of blood serum enables the transition to a deeply personalized approach in the diagnosis of these diseases while reducing the invasiveness and increasing the informativeness of analysis. This review discusses the technological approaches underlying the development of allergen microarrays and other protein microarrays, including the methods of selection of the microarray substrates and matrices for protein molecule immobilization, the obtainment of allergens, and the use of different types of optical labels for increasing the sensitivity and specificity of the detection of allergen-specific antibodies.

Enzymes on chemical gardens: Chemobrionics-based electrochemical biosensor

The relationship between biological materials and the immobilization matrix is a critical point in attaching biomolecules onto transducers in the preparation of biosensors. Various chemical molecules are used to conjugate biological compounds in the design of biofunctional surfaces. Among them, chemobrionics (CBCs) are good alternatives as an immobilization matrix to improve performance parameters such as linear range, limit of detection (LOD), stability, reproducibility, etc. Here, CBCs are used to develop enzymatic biosensor, and glucose oxidase (GOx) is selected as a model enzyme. Firstly, CBC is functionalized using (3-Aminopropyl)triethoxysilane (APTES) to obtain free amine groups for immobilization of GOx via covalent bonds. The synthesized CBC-APTES is used as a matrix for the conjugation of GOx using glutaraldehyde as a crosslinker. The proposed CBC-APTES/GOx is formed on the glassy carbon electrode, and its performance is checked for glucose detection. The linear range is 0.025–1.25 mM with an LOD of 0.024 mM glucose. After finding no effect of some potential interference on the current response, CBC-APTES/GOx is successfully applied to analyze glucose in artificial samples such as serum, urine, sweat, and saliva. The objective here is to outline the integration of CBC in biosensor preparation, which has been successfully carried out for the first time in the literature.

Characteristics of Novel Heterotrophic Nitrification–Aerobic Denitrification Bacteria Bacillus subtilis F4 and Alcaligenes faecalis P4 Isolated from Landfill Leachate Biochemical Treatment System

Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria are the key functional microorganisms needed to achieve simultaneous nitrification and denitrification (SND). In this study, 25 strains of HN-AD bacteria were successfully isolated from a stable landfill leachate biochemical treatment system, of which 10 strains belonged to Firmicutes and 15 strains belonged to Proteobacteria. Bacillus subtilis F4 and Alcaligenes faecalis P4 displayed good tolerance at a wide range of ammonia nitrogen (NH4+-N) concentrations. When the C/N ratio was 20, the removal rates of ammonia nitrogen were 90.1% and 89.5%, and the chemical oxygen demand (COD) removal rates were 92.4% and 93.9%, respectively. The napA gene encoding periplasmic nitrate reductase (Nap) and the nirS gene encoding nitrite reductase (Nir) were detected, and nitrogen balance showed assimilation and HN-AD was the main nitrogen metabolism mode in both strains. The use of immobilization materials could increase removal rate of ammonia nitrogen by 21.1% and 29.6%, respectively. The research results of this work can provide theoretical basis and technical support for the practical application of HN-AD bacteria to enhance the treatment of high ammonia nitrogen wastewater with high efficiency and low consumption.

Maltodextrin-modified hyperoxic graphene oxide as potential matrix for one-step purification and immobilization of MBP-tagged proteins

One-step purification and immobilization directly from crude extracts is a development trend to obtain high purity and performance target proteins due to the simple operation and high efficiency. Maltose binding protein (MBP)-tagged proteins usually need to be purified in biological experiments. It is very necessary to develop a low-cost, environmentally friendly and one-step purification and immobilization matrix. In this study, maltodextrin-modified hyperoxic graphene oxide (MHGO) was prepared using hyperoxic graphene oxide (HGO) and maltodextrin, which was characterized by scanning electron microscopy (SEM), (powder X-ray diffraction) PXRD and Fourier transform infrared spectroscopy (FTIR). MHGO was then used as a one-step purification and immobilization matrix to treat the crude extract and obtain MlrA@MHGO with 84.2 % purity of MlrA. The loading capacity of MHGO for MlrA was 379 ± 26 mg g−1 MHGO. Furthermore, the activity recovery of MlrA using the one-step strategy with MHGO as the matrix was found to be 26.5 times that of the two-step strategy. The Kcat value of MlrA@MHGO was 1.84 times that of free MlrA. Compared with free MlrA, MlrA@MHGO demonstrated enhanced stability, including half-life, thermal stability and pH stability, which were significantly improved than free MlrA. Based on these findings, we proposed a new paradigm for the purification and immobilization of MlrA using MHGO can be an effective matrix for the one-step purification and immobilization of MBP-tagged proteases.

Immobilization of &lt;i&gt;Azospirillum&lt;/i&gt; Bacteria on Various Carriers

A significant part of research in environmentally friendly agroindustrial production is aimed at immobilized bacterial preparations with retained capacity for active growth without loss of metabolic activity both during immobilization and after long-term storage and biotechnological use. In the present work, immobilization of members of the genus Azospirillum on natural and synthetic carriers was investigated. Efficiency of immobilization of the cells of A. brasilense strain SR80 in alginate hydrogel and vermiculite was investigated. Proliferative and metabolic activities of immobilized preparations were investigated. The prospects of using vermiculite and calcium alginate as matrices for Azospirillum immobilization are shown.

A Hydrophilic Metal Azolate Coordination Polymer for In Situ Encapsulation of Haloalkane Dehalogenase with Enhanced Enzymatic Performance.

Encapsulating enzymes within metal-organic frameworks such as zeolitic imidazolate framework-8 (ZIF-8) has been demonstrated to enhance enzymatic performance under harsh conditions. However, by computer-aided analysis, we revealed that highly hydrophobic organic ligands and unfavorable metal ions could greatly impair the activity of haloalkane dehalogenase DhaA by directly interacting with the catalytic sites, causing an extremely low activity of DhaA after encapsulating within ZIF-8. We also found that the presence of a protecting polymer could protect DhaA from the damage of organic ligands and metal ions and that a positively charged amino acid could increase the DhaA activity. Based on the simulations and experimental observations, we have designed to coencapsulate DhaA with poly(vinylpyrrolidone) (PVP) and lysine (Lys) within the amorphous Co-based metal azolate coordination polymer (CoCP). The as-prepared immobilized enzyme (DhaA/PVP/Lys@CoCP) exhibited significantly increased activity (91.5 times higher than that of DhaA@ZIF-8), dramatically enhanced thermostability at 50-70 °C, greatly improved catalytic performance in several organic solvent solutions, and good recyclability (over 75% of the initial activity after 10 cycles). The superiority of the immobilized enzyme was also demonstrated with a substrate frequently detected in the real world. In addition to the protective effect of PVP and positive effect of Lys, experimental and computational investigations unveiled other two favorable aspects that contributed to the enhanced enzymatic performance: (1) high hydrophilicity of the immobilization material and (2) the use of Co2+ with a minimal negative effect on DhaA. The research has thus provided a promising immobilized DhaA with favorable catalytic performance and great potential in industrial applications.

Effect of Sodium Oxide on Structure of Lanthanum Aluminosilicate Glass

Rare earth (RE) aluminosilicate glasses exhibit several favorable chemical, mechanical and thermal properties. As such, they are considered to be model systems for long-half-life actinides and are candidate containment materials for long-term immobilization of radioactive wastes. The aim of the present study was to investigate the effect of the substitution of sodium oxide on the glass transition temperature and structure of lanthanum aluminosilicate glasses. The primary objective was to elucidate the relationship between the substitution of Na2O for La2O3 on the Tg reduction and structural characteristics of lanthanum aluminosilicate glass, including identifying changes in the main Qn species and local environments of Si and Al. The structure of SiO2–Al2O3–La2O3–Na2O glasses has not been studied previously, and, thus, this investigation is the first to assess the structural changes occurring when La2O3 is substituted by Na2O. Three glasses were prepared with general composition (mol.%): 55SiO2–25Al2O3–20M2On (M = La or Na; n = 3 or 1). Glass G1 contains 20 mol.% La2O3; in G2, 15 mol.% of La2O3 was substituted by 15 mol.% Na2O; and Glass G3 contains 20 mol.% Na2O. The glasses were characterized by DSC to determine glass transition temperatures. As expected, as Na is substituted for La, Tg decreases substantially. Structural studies were carried out by FTIR spectroscopy, 29Si, and 27Al MAS NMR. As Na is substituted for La in these aluminosilicate glasses, the main goals that were achieved were the identification of Qn species and also changes in the local environments of Si and Al: {QnSi(mAl)} and {QnAl(mSi)}.

Innovative Microbial Immobilization Strategy for Di-n-Butyl Phthalate Biodegradation Using Biochar-Calcium Alginate-Waterborne Polyurethane Composites.

Di-n-butyl phthalate (DBP) is a prevalent phthalate ester widely used as a plasticizer, leading to its widespread presence in various environmental matrices. This study presents an innovative microbial immobilization strategy utilizing biochar, calcium alginate (alginate-Ca, (C12H14CaO12)n), and waterborne polyurethane (WPU) composites to enhance the biodegradation efficiency of DBP. The results revealed that rice husk biochar, pyrolyzed at 300 °C, exhibits relatively safer and more stable physical and chemical properties, making it an effective immobilization matrix. Additionally, the optimal cultural conditions for Bacillus aquimaris in DBP biodegradation were identified as incubation at 30 °C and pH 7, with the supplementation of 0.15 g of yeast extract, 0.0625 g of glucose, and 1 CMC of Triton X-100. Algal biotoxicity results indicated a significant decrease in biotoxicity, as evidenced by an increase in chlorophyll a content in Chlorella vulgaris following DBP removal from the culture medium. Finally, microbial community analysis demonstrated that encapsulating B. aquimaris within alginate-Ca and WPU layers not only enhanced DBP degradation, but also prevented ecological competition from indigenous microorganisms. This novel approach showcases the potential of agricultural waste utilization and microbial immobilization techniques for the remediation of DBP-contaminated environments.

Immobilization of collagenase in inorganic hybrid nanoflowers with enhanced stability, proteolytic activity, and their anti-amyloid potential

Organic-inorganic hybrid nanomaterials are considered as promising immobilization matrix for enzymes owing to their markedly enhanced stability and reusability. Herein, collagenase was chosen as a model enzyme to synthesize collagenase hybrid nanoflowers (Col-hNFs). Maximum collagenase activity (155.58 μmol min−1 L−1) and encapsulation yield (90 %) were observed in presence of Zn(II) ions at 0.05 mg/mL collagenase, 120 mM zinc chloride and PBS (pH 7.5). Synthesized Col-Zn-hNFs were extensively characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering (DLS) and zeta potential measurements. SEM images showed flower-like morphology with average size of 5.1 μm and zeta potential of −14.3 mV. Col-Zn-hNFs demonstrated superior relative activity across wide pH and temperature ranges, presence of organic solvents and surfactants as compared to its free form. Moreover, Col-Zn-hNFs exhibited excellent shelf life stability and favorable reusability. Col-Zn-hNFs showed the ability to suppress and eradicate fully developed insulin fibrils in vitro (IC50 = 2.8 and 6.2 μg/mL, respectively). This indicates a promising inhibitory potential of Col-Zn-hNFs against insulin amyloid fibrillation. The findings suggest that the utilization of Col-Zn-hNFs as a carrier matrix holds immense potential for immobilizing collagenase with improved catalytic properties and biomedical applications.

Carbon dots functionalized polyaniline as efficient sensing platform for cancer biomarker detection

Implementing simple and rapid detection of cancer biomarker using biosensors has the potential to contribute greatly to basic biological research and early detection of cancer. Tailoring of biosensor matrix based on conducting polymers has gained significant attention in recent years due to its electroactivity, redox property and biocompatibility. Herein, biomass derived carbon dots (CDs) were anchored on polyaniline (PANI) surface to get biocompatible and fluorescent, carbon dots functionalized polyaniline (CDs@PANI) that enable binding of large amount of prostate cancer biomarker, prostate specific antigen (PSA) antibody on its surface via active functional groups. Immobilization efficiency of CDs@PANI was investigated by electrochemical methods which revealed dense immobilization of biomolecules on CDs@PANI as compared to conventional PANI. A sandwich electrochemical biosensor was constructed using CDs@PANI as immobilization matrix for detection of prostate cancer biomarker PSA. The sensor displayed good sensitivity, specificity, stability, reproducibility, wide linear range (0.01–60 ng/ml) and a low detection limit of 20 pg/ml. The importance of CDs in improving the sensor performance was demonstrated by carrying out detailed electrochemical studies using glucose oxidase as a model biomolecule. Biocompatibility of sensing matrix was assessed by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay for cell viability using WI26 cells. The sensing platform demonstrated herein provides great potential for the detection of different cancer biomarkers and metabolites.

Development of Technology for the Bioleaching of Uranium in a Solution of Bacterial Immobilization

This study presents findings regarding the kinetics of ferrous iron oxidation in solution mediated by Acidithiobacillus ferrooxidans bacteria within a continuous-flow bioreactor employing diverse types of immobilizers. The objective is to augment the rate of ferrous iron oxidation in solutions utilizing an immobilizer for Acidithiobacillus ferrooxidans strains. Immobilization represents a promising avenue for enhancing the efficiency of Fe2⁺ oxidation via acidophilic ferrooxidizing bacteria, leading to a several-fold increase in oxidation rate. A comparative analysis was conducted to evaluate the efficacy of different types of immobilizer in facilitating iron oxidation within a continuous-flow bioreactor, including the application of wood chips coated with Fe(OH)3. The results indicate that wood chips coated with iron hydroxide serve as effective type of immobilizer, facilitating the robust attachment of Acidithiobacillus ferrooxidans via electrostatic interactions between negatively charged bacteria and positively charged surfaces. Experimental investigations were conducted using novel immobilization matrices in pilot-scale tests simulating the underground borehole leaching (UBL) of uranium. The bioactivation of leaching solutions enhances the efficiency and environmental compatibility of UBL compared to conventional chemical oxidation methods. The relationships between redox potential and ferric iron content in bioactivated solutions during the UBL of uranium were delineated. The significance of this study lies in its elucidating the pivotal role of Fe2⁺ oxidation in uranium extraction processes, particularly in the context of UBL. By employing bioactivation mediated by Acidithiobacillus ferrooxidans, the study demonstrates not only enhanced uranium extraction efficiency, but also markedly improved environmental sustainability compared to traditional chemical oxidation methods. The findings reveal crucial correlations between redox potential and ferric iron concentration in bioactivated solutions.

CaO-modified hydrochar reduces soil cadmium bioavailability by altering soil properties, shifting bacterial community, and promoting microbial metabolisms

The efficient remediation of cadmium (Cd)-contaminated soil is of great significance for reducing the threats to ecosystem and human health. At present, the carbon-rich hydrochar with abundant oxygen-containing functional groups as environmental remediation material gains numerous attention due to its cost-effectiveness and sustainability. A pot experiment was performed to investigate the Cd immobilization efficiency and microbial response in soil with the presence of pristine corn stalk hydrochar and CaO-modified hydrochars. Results showed that compared with pristine hydrochar, fresh biomass of plant shoot was promoted by 0.904–15.6% with CaO-modified hydrochar amendment, and the bioavailable Cd content and correspoding Cd uptake by shoot were decreased by 8.19–16.2% and 4.18–17.0%, respectively. Additionally, the relative abundance of Actinobacteriota benefiting Cd immobilization in soil was elevated from 30.3% to 34.4–44.6% after CaO-modified hydrochar amendment. The microbial metabolisms (e.g., carbohydrate metabolism, amino acid metabolism, and citrate cycle) were also enhanced by CaO-modified hydrochar, contributing to reduce Cd bioavailability. Redundancy analysis revealed that bacterial community structure in rhizosphere soil was significantly influenced by soil dissolved organic carbon and electric conductivity (p＜0.05). Overall, the cost-effective CaO-modified hydrochar with reduced phytotoxicity was a promising remediation material for Cd immobilization in metal-contaminated soil.