Brown algal cell walls and development.

Brown algae are complex multicellular eukaryotes whose cells possess a cell wall, which is an important structure that regulates cell size and shape. Alginate and fucose-containing sulfated polysaccharides (FCSPs) are two carbohydrate types that have major roles in influencing the mechanical properties of the cell wall (i.e. increasing or decreasing wall stiffness), which in turn regulate cell expansion, division, adhesion, and other processes; however, how brown algal cell wall structure regulates its mechanical properties, and how this relationship influences cellular growth and organismal development, is not well-understood. This chapter is focused on reviewing what we currently know about how the roles of alginates and FCSPs in brown algal developmental processes, as well as how they influence the structural and mechanical properties of cell walls. Additionally, we discuss how brown algal mutants may be leveraged to learn more about the underlying mechanisms that regulate cell wall structure, mechanics, and developmental processes, and finally we propose questions to guide future research with the use of emerging technologies.

Flip the switch: the role of FleQ in modulating the transition between the free-living and sessile mode of growth in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen causing chronic infections that are associated with the sessile/biofilm mode of growth rather than the free-living/planktonic mode of growth. The transcriptional regulator FleQ contributes to both modes of growth by functioning both as an activator and repressor and inversely regulating flagella genes associated with the planktonic mode of growth and genes contributing to the biofilm mode of growth. Here, we review findings that enhance our understanding of the molecular mechanism by which FleQ enables the transition between the two modes of growth. We also explore recent advances in the mechanism of action of FleQ to both activate and repress gene expression from a single promoter. Emphasis will be on the role of sigma factors, cyclic di-GMP, and the transcriptional regulator AmrZ in inversely regulating flagella and biofilm-associated genes and converting FleQ from a repressor to an activator.

ICA/SDF-1α/PBMSCs loaded onto alginate and gelatin cross-linked scaffolds promote damaged cartilage repair.

A three-dimensional alginate-coated scaffold (GAIS) was constructed in the present study to showcase the multidifferentiation potential of peripheral blood mesenchymal stem cells (PBMSCs) and to investigate the role and mechanism by which Icariin (ICA)/stromal cell-derived factor (SDF-1α)/PBMSCs promote damaged articular repair. In addition, the ability of ICA, in combination with SDF-1α, to promote the migration and proliferation of stem cells was validated through the utilization of CCK-8 and migration experiments. The combination of ICA and SDF-1α inhibited the differentiation of PBMSCs into cartilage, as demonstrated by in vivo experiments and histological staining. Both PCR and western blot experiments showed that GAIS could upregulate the expression of particular genes in chondrocytes. In comparison to scaffolds devoid of alginate (G0), PBMSCs seeded into GAIS scaffolds exhibited a greater rate of proliferation, and the conditioned medium derived from scaffolds containing SDF-1α enhanced the capacity for cell migration. Moreover, after a 12-week treatment period, GAIS, when successfully transplanted into osteochondral defects of mice, was found to promote cartilage regeneration and repair. The findings, therefore, demonstrate that GAIS enhanced the in vitro capabilities of PBMSCs, including proliferation, migration, homing and chondrogenic differentiation. In addition, ICA and SDF-1α effectively collaborated to support cartilage formation in vivo. Thus, the ICA/SDF-1α/PBMSC-loaded biodegradable alginate-gelatin scaffolds showcase considerable potential for use in cartilage repair.

Pseudomonas aeruginosa AlgF is a protein-protein interaction mediator required for acetylation of the alginate exopolysaccharide.

Enzymatic modifications of bacterial exopolysaccharides enhance immune evasion and persistence during infection. In the Gram-negative opportunistic pathogen Pseudomonas aeruginosa, acetylation of alginate reduces opsonic killing by phagocytes and improves reactive oxygen species scavenging. Although it is well known that alginate acetylation in P. aeruginosa requires AlgI, AlgJ, AlgF, and AlgX, how these proteins coordinate polymer modification at a molecular level remains unclear. Here, we describe the structural characterization of AlgF and its protein interaction network. We characterize direct interactions between AlgF and both AlgJ and AlgX in vitro and demonstrate an association between AlgF and AlgX, as well as AlgJ and AlgI, in P. aeruginosa. We determine that AlgF does not exhibit acetylesterase activity and is unable to bind to polymannuronate in vitro. Therefore, we propose that AlgF functions to mediate protein-protein interactions between alginate acetylation enzymes, forming the periplasmic AlgJFXK (AlgJ-AlgF-AlgX-AlgK) acetylation and export complex required for robust biofilm formation.

Identification and structural analysis of a carbohydrate-binding module specific to alginate, a representative of a new family, CBM96.

Carbohydrate-binding modules (CBMs) are the noncatalytic modules that assist functions of the catalytic modules in carbohydrate-active enzymes, and they are usually discrete structural domains in larger multimodular enzymes. CBMs often occur in tandem in different alginate lyases belonging to the CBM families 13, 16, and 32. However, none of the currently known CBMs in alginate lyases specifically bind to an internal alginate chain. In our investigation of the multidomain alginate lyase Dp0100 carrying several ancillary domains, we identified an alginate-binding domain denoted TM6-N4 using protein truncation analysis. The structure of this CBM domain was determined at 1.35 Å resolution. TM6-N4 exhibited an overall ß-sandwich fold architecture with two antiparallel ß-sheets. We identified an extended binding groove in the CBM using site-directed mutagenesis, docking, and surface electrostatic potential analysis. Affinity analysis revealed that residues of Lys10, Lys22, Lys25, Lys27, Lys31, Arg36, and Tyr159 located on the bottom or the wall of the shallow groove are responsible for alginate binding, and isothermal titration calorimetry analyses indicated that the binding cleft consists of six subsites for sugar recognition. This substrate binding pattern is typical for type B CBM, and it represents the first CBM domain that specifically binds internal alginate chain. Phylogenetic analysis supports that TM6-N4 constitutes the founding member of a new CBM family denoted as CBM96. Our reported structure not only facilitates the investigation of the CBM-alginate ligand recognition mechanism but also inspires the utilization of the CBM domain in biotechnical applications.

Characterization of ERα Signaling to Cell Proliferation Induced by Chronic and Pulsatile E2 Stimulation in 2D and 3D Cell Cultures.

17ß-estradiol is a hormone that plays a vital role in human physiology. It acts through estrogen receptors, specifically estrogen receptor α and estrogen receptor ß, and its action is determined by the pulsatile secretion in the bloodstream. 17ß-estradiol affects cell proliferation, and dysregulation of 17ß-estradiol:estrogen receptor α signaling contribute to the development of breast cancer. Previous research on 17ß-estradiol:estrogen receptor α signaling has primarily used two-dimensional cell cultures, which do not fully recapitulate the complexity of tumors that exist in a three-dimensional environment and do not consider the pulsatile nature of this hormone. To address these limitations, we studied 17ß-estradiol:estrogen receptor α signaling in cell proliferation using both two-dimensional and three-dimensional breast cancer cell culture models under continuous and pulsatile stimulation conditions. Results revealed that breast cancer cells grown in an alginate-based three-dimensional matrix exhibited similar responsiveness to 17ß-estradiol compared with cells grown in conventional two-dimensional culture plates. 17ß-estradiol induced the expression of proteins containing estrogen response element in the three-dimensional model. The efficacy of the antiestrogen drugs fulvestrant (ICI182,280) and 4OH-tamoxifen was also demonstrated in the three-dimensional model. These results support the use of the three-dimensional culture model for studying tumor response to drugs and provide a more realistic microenvironment for such studies. Furthermore, the study revealed that a brief 5-min exposure to 17ß-estradiol triggered a physiological response comparable with continuous hormone exposure, suggesting that the cellular response to 17ß-estradiol is more important than the continuous presence of the hormone. In conclusion, the study demonstrates that the alginate-based three-dimensional culture model is suitable for studying the effects of 17ß-estradiol and antiestrogen drugs on breast cancer cells, offering a more realistic representation of tumor-microenvironment interactions. The results also highlight the importance of considering the physiological importance of the temporal dynamics in studying 17ß-estradiol signaling and cellular responses.

Alginate Improves the Chondrogenic Capacity of 3D PCL Scaffolds In Vitro: A Histological Approach.

Polycaprolactone (PCL) scaffolds have demonstrated an effectiveness in articular cartilage regeneration due to their biomechanical properties. On the other hand, alginate hydrogels generate a 3D environment with great chondrogenic potential. Our aim is to generate a mixed PCL/alginate scaffold that combines the chondrogenic properties of the two biomaterials. Porous PCL scaffolds were manufactured using a modified salt-leaching method and embedded in a culture medium or alginate in the presence or absence of chondrocytes. The chondrogenic capacity was studied in vitro. Type II collagen and aggrecan were measured by immunofluorescence, cell morphology by F-actin fluorescence staining and gene expression of COL1A1, COL2A1, ACAN, COL10A1, VEGF, RUNX1 and SOX6 by reverse transcription polymerase chain reaction (RT-PCR). The biocompatibility of the scaffolds was determined in vivo using athymic nude mice and assessed by histopathological and morphometric analysis. Alginate improved the chondrogenic potential of PCL in vitro by increasing the expression of type II collagen and aggrecan, as well as other markers related to chondrogenesis. All scaffolds showed good biocompatibility in the in vivo model. The presence of cells in the scaffolds induced an increase in vascularization of the PCL/alginate scaffolds. The results presented here reinforce the benefits of the combined use of PCL and alginate for the regeneration of articular cartilage.

Oral administration of DNA alginate nanovaccine induced immune-protection against Helicobacter pylori in Balb/C mice.

BACKGROUND: Helicobacter pylori (H. Pylori), is an established causative factor for the development of gastric cancer and the induction of persistent stomach infections that may lead to peptic ulcers. In recent decades, several endeavours have been undertaken to develop a vaccine for H. pylori, although none have advanced to the clinical phase. The development of a successful H. pylori vaccine is hindered by particular challenges, such as the absence of secure mucosal vaccines to enhance local immune responses, the absence of identified antigens that are effective in vaccinations, and the absence of recognized indicators of protection. METHODS: The DNA vaccine was chemically cloned, and the cloning was verified using PCR and restriction enzyme digestion. The efficacy of the vaccination was investigated. The immunogenicity and immune-protective efficacy of the vaccination were assessed in BALB/c mice. This study demonstrated that administering a preventive Alginate/pCI-neo-UreH Nanovaccine directly into the stomach effectively triggered a robust immune response to protect against H. pylori infection in mice. RESULTS: The level of immune protection achieved with this nano vaccine was similar to that observed when using the widely accepted formalin-killed H. pylori Hel 305 as a positive control. The Alginate/pCI-neo-UreH Nanovaccine composition elicited significant mucosal and systemic antigen-specific antibody responses and strong intestinal and systemic Th1 responses. Moreover, the activation of IL-17R signaling is necessary for the defensive Th1 immune responses in the intestines triggered by Alginate/pCI-neo-UreH. CONCLUSION: Alginate/pCI-neo-UreH is a potential Nanovaccine for use in an oral vaccine versus H. pylori infection, according to our findings.

Oral administration of PEDV-dissolved Alg-CS gel induces high and sustained mucosal immunity in mice.

Porcine epidemic diarrhea (PED) is a serious disease in piglets that leads to high mortality. An effective measure that provides higher IgA levels in the intestine and milk is required to decrease losses. Porcine epidemic diarrhea virus (PEDV) was dissolved in calcium alginate (Alg) and combined with chitosan (CS) via electrostatic interactions between cationic chitosan and anionic alginate to create a porous gel (Alg-CS+PEDV). The gel was used to immunize mice orally or in combination with subcutaneous injections of inactivated PEDV vaccine. At 12 and 24 days after immunization, levels of IgA and IgG in Alg-CS+PEDV were higher than with normal PEDV oral administration. At 24 days after immunization, the concentration of IFN-γ in Alg-CS+PEDV was higher than with normal PEDV oral administration. Furthermore, oral administration combining subcutaneous immunization induced higher levels of IgG and IgA than oral administration alone. Our study provides a new method for the preparation and administration of oral vaccines to achieve enhanced mucosal immunity against PEDV.

Role of gamma-irradiated sodium alginate on growth, physiological and active components of iceberg lettuce (Lactuca sativa) plant.

BACKGROUND: One of the most widely recognized biostimulators of plant development; is oligoalginate, which regulates the biological processes of plants and was used in horticultural fields as a plant growth regulator. The plan of the current research was to study, however, the foliar application of un-irradiated and irradiated Na-alginate (UISA and ISA) to improve the growth, physiological activity, and other active components of the Egyptian iceberg lettuce plant. Degraded Na-alginate is equipped with exposure of sodium alginate in its solid state to gamma-rays at different dose levels (0.0, 25, 50, 75, and 100 kGy). The characterization of the oligo-alginates achieved by γ-radiation deprivation at different dose levels was performed by FTIR, XRD, TGA, SEM, and TEM. Different concentrations of irradiated sodium alginate at dose levels of 100 kGy (200, 400, 600, and 800 ppm, as well as deionized water used as a control) were sprayed with a hand sprayer every week after transplanting the iceberg lettuce seedlings in the field until the harvest stage. Morphological traits were evaluated, as well as pigments, ascorbic acid, phenols, flavonoids, soluble proteins, and antioxidant activity. RESULTS: Irradiated Na-alginate resulted in the depolymerization of Na-alginate into small molecular-weight oligosaccharides, and the best dose to use was 100 kGy. Certain chemical modifications in the general structure were observed by FTIR analysis. Two absorbed bands at 3329 cm-1 and 1599 cm-1, were recognized that are assigned to O-H and C-O stretching, respectively, and peaks achieved at 1411 cm-1 represent the COO-stretching group connected to the sodium ion. The peak obtained at 1028 cm-1 was owing to the stretching vibration of C-O. The results of TGA provided that the minimum weight reminder was in the ISA at 100 kGy (28.12%) compared to the UISA (43.39%). The images of TEM pointed out that the Na-alginate was globular in shape, with the particle distribution between 12.8 and 21.7 nm in ISA at 100 kGy. Irradiated sodium alginate caused a noteworthy enhancement in the vegetative growth traits (leaf area, stem length, head weight, and leaf number). By spraying 400 ppm, ISA showed a maximum increase in total pigments (2.209 mg/g FW), ascorbic acid (3.13 mg/g fresh weight), phenols (1.399 mg/g FW), flavonoids (0.775 mg/g FW), and antioxidant activities (82.14. %). Also, there were correlation coefficients (R values) between leaf area, stem length, head weight, and leaf number values with total pigment content, antioxidant activity, total soluble proteins, and ascorbic acid. CONCLUSIONS: The outcomes of the recent investigation demonstrated that the application of spraying irradiated Na-alginate (100 kGy) resulted in an improvement of the considered characters.

Controllable and Reversible Assembly of Nanofiber from Natural Macromolecules via Protonation and Deprotonation.

Nanofiber is the critical building block for many biological systems to perform various functions. Artificial assembly of molecules into nanofibers in a controllable and reversible manner will create "smart" functions to mimic those of their natural analogues and fabricate new functional materials, but remains an open challenge especially for nature macromolecules. Herein, the controllable and reversible assembly of nanofiber (CSNF) from natural macromolecules with oppositely charged groups are successfully realized by protonation and deprotonation of charged groups. By controlling the electrostatic interaction via protonation and deprotonation, the size and morphology of the assembled nanostructures can be precisely controlled. A strong electrostatic interaction contributes to large nanofiber with high strength, while poor electrostatic interaction produces finer nanofiber or nanoparticle. And especially, the assembly, disassembly, and reassembly of the nanofiber occurs reversibly through protonation and deprotonation, thereby paving a new way for precisely controlling the assembly process and structure of nanofiber. The reversible assembly allows the nanostructure to dynamically reorganize in response to subtle perturbation of environment. The as-prepared CSNF is mechanical strong and can be used as a nano building block to fabricate high-strength film, wire, and straw. This study offers many opportunities for the biomimetic synthesis of new functional materials.

3D-Printed Hydrogels with High-Strength and Anisotropy Mediated by Chain Rigidity.

Extrusion-based 3D printing is a facile technology to construct complex structures of hydrogels, especially for tough hydrogels that have shown demonstrated potential in load-bearing materials and tissue engineering. However, 3D-printed hydrogels often possess mechanical properties that do not guarantee their usage in tissue-mimicking, load-bearing components, and motion sensors. This study proposes a novel strategy to construct high-strength and anisotropic Fe3+ cross-linked poly(acrylamide-co-acrylic acid)/sodium alginate double network hydrogels. The semi-flexible sodium alginate chains act as a "conformation regulator" to promote the formation of strong intermolecular interactions between polymer chains and lock the more extended conformation exerted by the pre-stretch, enabling the construction of 3D-printed hydrogel structures with high orientation. The equilibrated anisotropic hydrogel filaments with a water content of 50-60 wt.% exhibit outstanding mechanical properties (tensile strength: 9-44 MPa; elongation at break: 120-668%; Young's modulus: 7-62 MPa; toughness: 26-52 MJ m- 3). 3D-printed anisotropic hydrogel structures with high mechanical performance show demonstrated potential as loading-bearing structures and electrodes of flexible triboelectric nanogenerators for versatile human motion sensing.

Tortuosity Engineering of Water Channels to Customized Water Supply for Enhancing Hydrogel Solar Evaporation.

Hydrogel as a solar evaporator shows great potential in freshwater production. However, hydrogels often lead to an imbalance between solar energy input and water supply management due to their excessively high saturated water content. Thus, achieving a stable water-energy-balance in hydrogel evaporators remains challenging. Here, by tortuosity engineering designed water transport channels, a seamless high-tortuosity/low-tortuosity/high-tortuosity structured hydrogel (SHLH structure hydrogel) evaporator is developed, which enables the hydrogel with customized water transport rate, leading to the controlled water supply at the evaporator interface. An excellent equilibrium between the photothermal conversion and water supply is established, and the maximum utilization of solar energy is realized, thereby achieving an excellent evaporation rate of 3.64 kg m-2 h-1 under one solar illumination. This tortuosity engineering controlled SHLH structured evaporator provides a novel strategy to attain water-energy-balance and expands new approaches for constructing hydrogel-based evaporators with tailored water transportation capacity.

A Super-Hygroscopic Solar-Regenerated Alginate-Based Composite for Atmospheric Water Harvesting.

Global water scarcity is leading to increasingly tense competition across populations. In order to complement the largely fast-depleting fresh water sources and mitigate the challenges generated by brine discharge from desalination, atmospheric water harvesting (AWH) has emerged to support long-term water supply. This work presents a novel alginate-based hybrid material comprised of porous silico-aluminophosphate-34 (SAPO-34) as fast-transport channel medium as well as hydrophilicity and stability enhancer, and graphene-based sheets as light absorber for solar-enabled evaporation, both optimally incorporated in an alginate matrix, resulting in a composite sorbent capable of harvesting water from the atmosphere with a record intake of up to 6.85 gw gs -1. Natural sunlight is solely used to enable desorption achieving increase of the temperature of the developed network up to 60 °C and resulting in release of the sorbed water, with impurities content well below the World Health Organization (WHO) upper limits. After 30 cycles of sorption and desorption, the composite hydrogel displayed unchanged water uptake and stability. This work provides an impactful perspective toward sustainable generation of water from humidity without external energy consumption supporting the emergence of alternative water production solutions.

Alginate oligosaccharide assimilation by gut microorganisms and the potential role in gut inflammation alleviation.

Dietary fiber metabolism by gut microorganisms plays important roles in host physiology and health. Alginate, the major dietary fiber of daily diet seaweeds, is drawing more attention because of multiple biological activities. To advance the understanding of alginate assimilation mechanism in the gut, we show the presence of unsaturated alginate oligosaccharides (uAOS)-specific alginate utilization loci (AUL) in human gut microbiome. As a representative example, a working model of the AUL from the gut microorganism Bacteroides clarus was reconstructed from biochemistry and transcriptome data. The fermentation of resulting monosaccharides through Entner-Doudoroff pathway tunes the metabolism of short-chain fatty acids and amino acids. Furthermore, we show that uAOS feeding protects the mice against dextran sulfate sodium-induced acute colitis probably by remodeling gut microbiota and metabolome. IMPORTANCE: Alginate has been included in traditional Chinese medicine and daily diet for centuries. Recently discovered biological activities suggested that alginate-derived alginate oligosaccharides (AOS) might be an active ingredient in traditional Chinese medicine, but how these AOS are metabolized in the gut and how it affects health need more information. The study on the working mechanism of alginate utilization loci (AUL) by the gut microorganism uncovers the role of unsaturated alginate oligosaccharides (uAOS) assimilation in tuning short-chain fatty acids and amino acids metabolism and demonstrates that uAOS metabolism by gut microorganisms results in a variation of cell metabolites, which potentially contributes to the physiology and health of gut.

Metagenomic insights into the dynamic degradation of brown algal polysaccharides by kelp-associated microbiota.

Marine bacteria play important roles in the degradation and cycling of algal polysaccharides. However, the dynamics of epiphytic bacterial communities and their roles in algal polysaccharide degradation during kelp decay are still unclear. Here, we performed metagenomic analyses to investigate the identities and predicted metabolic abilities of epiphytic bacterial communities during the early and late decay stages of the kelp Saccharina japonica. During kelp decay, the dominant epiphytic bacterial communities shifted from Gammaproteobacteria to Verrucomicrobia and Bacteroidetes. In the early decay stage of S. japonica, epiphytic bacteria primarily targeted kelp-derived labile alginate for degradation, among which the gammaproteobacterial Vibrionaceae (particularly Vibrio) and Psychromonadaceae (particularly Psychromonas), abundant in alginate lyases belonging to the polysaccharide lyase (PL) families PL6, PL7, and PL17, were key alginate degraders. More complex fucoidan was preferred to be degraded in the late decay stage of S. japonica by epiphytic bacteria, predominantly from Verrucomicrobia (particularly Lentimonas), Pirellulaceae of Planctomycetes (particularly Rhodopirellula), Pontiellaceae of Kiritimatiellota, and Flavobacteriaceae of Bacteroidetes, which depended on using glycoside hydrolases (GHs) from the GH29, GH95, and GH141 families and sulfatases from the S1_15, S1_16, S1_17, and S1_25 families to depolymerize fucoidan. The pathways for algal polysaccharide degradation in dominant epiphytic bacterial groups were reconstructed based on analyses of metagenome-assembled genomes. This study sheds light on the roles of different epiphytic bacteria in the degradation of brown algal polysaccharides.IMPORTANCEKelps are important primary producers in coastal marine ecosystems. Polysaccharides, as major components of brown algal biomass, constitute a large fraction of organic carbon in the ocean. However, knowledge of the identities and pathways of epiphytic bacteria involved in the degradation process of brown algal polysaccharides during kelp decay is still elusive. Here, based on metagenomic analyses, the succession of epiphytic bacterial communities and their metabolic potential were investigated during the early and late decay stages of Saccharina japonica. Our study revealed a transition in algal polysaccharide-degrading bacteria during kelp decay, shifting from alginate-degrading Gammaproteobacteria to fucoidan-degrading Verrucomicrobia, Planctomycetes, Kiritimatiellota, and Bacteroidetes. A model for the dynamic degradation of algal cell wall polysaccharides, a complex organic carbon, by epiphytic microbiota during kelp decay was proposed. This study deepens our understanding of the role of epiphytic bacteria in marine algal carbon cycling as well as pathogen control in algal culture.

Hydroxyapatite-loaded macroporous calcium alginate hydrogels: Preparation, characterization, and in vitro evaluation.

Hydrogels from natural polysaccharides are of great interest for tissue engineering. This study aims (1) to prepare hydroxyapatite-loaded macroporous calcium alginate hydrogels by novel one-step technique using internal gelation in water-frozen solutions; (2) to evaluate their physicochemical properties; (3) to estimate their ability to support cell growth and proliferation in vitro. The structure of the hydrogel samples in a swollen state was studied by confocal laser scanning microscopy and was shown to represent a system of interconnected macropores with sizes of tens micron. The swelling behavior of the hydrogels, their mechanical properties (Young's moduli) in function of a hydroxyapatite content (5-30 mass%) were studied. All hydrogel samples loaded with hydroxyapatite were found to support growth and proliferation of mouse fibroblasts (L929) at long-term cultivation for 7 days. The obtained macroporous composite Ca-Alg-HA hydrogels could be promising for tissue engineering.

The influence of sodium alginate on the structural and adsorption properties of resorcinol-formaldehyde resins and their porous carbon derivatives.

A series of carbon composites were synthesised by carbonisation of resorcinol-formaldehyde resin mixtures with the addition of different amounts of sodium alginate (SA) and compared with a composite prepared using Na2 CO3 as a catalyst for the polymerisation reaction. The effect of operating parameters such as SA concentration and polycondensation time on the structural and morphological properties of resorcinol-formaldehyde resins (RFR) and carbon-derived composites was investigated for further use as adsorbents. The synthesised composites were characterised by FTIR, SEM, Raman spectroscopy and N2 adsorption/desorption techniques. It was found that the morphology, specific surface area (SBET ~347-559 m2 /g), volume and particle size distribution (~0.5-4 µm) and porosity (Vpor =0.178-0.348 cm3 /g) of the composites were influenced by the concentration of SA and the synthesis technique and determined the adsorption properties of the materials. It was found that the surface of the filled chars was found to have an affinity for heavy metals and has the ability to form chemical bonds with cadmium ions. The maximum sorption capacities for Cd(II), i. e. 13.28 mg/g, were observed for the sample synthesised with the highest SA content. This confirms the statement that as-synthesised materials are promising adsorbents for environmental applications.

Enzyme-functionalized alginate microparticles enable anaerobic culture under ambient oxygen.

Methods for culturing oxygen-sensitive cells and organisms under anaerobic conditions are vital to biotechnology research. Here, we report a biomaterial-based platform for anaerobic culture that consists of glucose oxidase (GOX) functionalized alginate microparticles (ALG-GOX), which are designed to deplete dissolved [O2 ] through enzymatic activity. ALG-GOX microparticles were synthesized via a water-in-oil emulsion and had a size of 132.0 ± 51.4 µm. Despite having a low storage modulus, the microparticles remained stable under aqueous conditions due to covalent crosslinking through amide bonds. Enzyme activity was tunable based on the loaded GOX concentration, with a maximum activity of 3.6 ± 0.3 units/mg of microparticles being achieved at an initial loading concentration of 5 mg/mL of GOX in alginate precursor solution. High enzyme activity in ALG-GOX microparticles resulted in rapid oxygen depletion, producing a suitable environment for anaerobic culture. Microparticles loaded with both GOX and catalase (ALG-GOX-CAT) to reduce H2 O2 buildup exhibited sustained activity for potential long-term anaerobic culture. ALG-GOX-CAT microparticles were highly effective for the anaerobic culture of Bacteroides thetaiotaomicron, with 10 mg/mL of ALG-GOX-CAT microparticles supporting the same level of growth in an aerobic environment compared to an anaerobic chamber after 16 h (8.70 ± 0.96 and 10.03 ± 1.03 million CFU, respectively; N.S. p = 0.07). These microparticles could be a valuable tool for research and development in biotechnology.

Novel melanin-derived stationary phase for immobilized metal ion affinity chromatography in recombinant His-tagged protein purification.

The matrix of the stationary phase is a crucial element in affinity chromatography for protein purification. Various materials, including polymer or magnetic materials, have been employed as the matrix in the purification of His-tagged protein. Here, for the first time, we utilized a combination of melanin and alginate, both natural polymer materials, to synthesize Ni-melanin/alginate (Ni-M/A) beads for His-tagged protein purification. We investigated the binding of His-tagged Mpro on the Ni-M/A beads, referred to as Ni-M/A-Mpro, and assessed the elution efficiency of Mpro from the beads. Our examination involved FTIR, EDS, XRD, SDS-PAGE, and Western blotting methods. FTIR spectra revealed notable changes in the stretching patterns and intensities of hydroxyl, amine, carbonyl, imine and amide chemical groups, when Mpro protein was present in the Ni-M/A sample. XRD spectra demonstrated the occurrence of two Nickel peaks at 35-40 deg and 40-45 deg in Ni-M/A, but only one nickel peak at 35-40 deg in Ni-M/A-Mpro, indicating the binding of Mpro on the Nickel ions. EDS analysis reported a decrease in the concentration of Nickel on the surface of Ni-M/A from 16% to 7% when Mpro protein was loaded into the stationary phase. Importantly, our data indicated that the purity of the His-tagged protein Mpro after purification reached 97% after just one-step purification using the Ni-M/A stationary phase. Moreover, the binding capacity of Ni-M/A for Mpro was approximately 5.2 mg/g with recovery efficiency of 40%. Our results suggested Ni-M/A as a highly potential solid phase for affinity chromatography in the purification of His-tagged protein.