Optimization of alginate alkaline extraction technology from Sargassum latifolium and its potential antioxidant and emulsifying properties

Seaweed-derived laminarin and alginate as potential chemotherapeutical agents: An updated comprehensive review considering cancer treatment

Seaweed-derived bioactive substances such as polysaccharides have proven to be effective chemotherapeutic and chemopreventive agents. Laminarin and alginate antioxidant properties aid in the prevention of cancer through dynamic modulation of critical intracellular signaling pathways via apoptosis which produce low cytotoxicity and potential chemotherapeutic effects. Understanding the effects of laminarin and alginate on human cancer cells and their molecular roles in cell death pathways can help to develop a novel chemoprevention strategy. This review emphasizes the importance of apoptosis-modulating laminarin and alginate in a range of malignancies as well as their extraction, molecular structure, and weight. In addition, future nano-formulation enhancements for greater clinical efficacy are discussed. Laminarin and alginate are perfect ingredients because of their distinct physicochemical and biological characteristics and their use-based delivery systems in cancer. The effectiveness of laminarin and alginate against cancer and more preclinical and clinical trials will open up as new chemotherapeutic natural drugs which lead to established as potential cancer drugs.

Characterization of Unfractionated Polysaccharides in Brown Seaweed by Methylation-GC-MS-Based Linkage Analysis

This study introduces a novel approach to analyze glycosidic linkages in unfractionated polysaccharides from alcohol-insoluble residues (AIRs) of five brown seaweed species. GC-MS analysis of partially methylated alditol acetates (PMAAs) enables monitoring and comparison of structural variations across different species, harvest years, and tissues with and without blanching treatments. The method detects a wide array of fucose linkages, highlighting the structural diversity in glycosidic linkages and sulfation position in fucose-containing sulfated polysaccharides. Additionally, this technique enhances cellulose quantitation, overcoming the limitations of traditional monosaccharide composition analysis that typically underestimates cellulose abundance due to incomplete hydrolysis of crystalline cellulose. The introduction of a weak methanolysis-sodium borodeuteride reduction pretreatment allows for the detection and quantitation of uronic acid linkages in alginates.

Optimization and characterization of brown seaweed alginate for antioxidant, anticancer, antimicrobial, and antiviral properties

Alginate is a natural polysaccharide obtained from brown seaweeds and having advantageous health usefulness, was employed extensively in nutraceutical sectors and the pharmaceutical industry. This research was devoted for optimization of alginate extraction from different brown seaweeds. A Box-Behnken Design (BBD) was used for the optimization of alginate extraction from Padina pavonica by analyzing the influence of temperature (30, 40, and 50 °C), time (60, 120, and 180 min), and alkaline concentration (1 %, 2 %, and 3 %) on extraction yield and uronic acid content. The optimal conditions recorded to maximize the alginate yield and its uronic content were an alkali concentration of 2.5 % and a temperature of 39.95 °C for 102.5 min. The optimized parameters achieved from BBD were used to compare alginate extraction from P. pavonica, Sargassum cinereum, Turbinaria turbinata, and Dictyota dichotoma. FTIR, 1H NMR, and HPLC were used to characterize the extracted alginate. The bioactivity of alginate against free radicals, breast cancer cells (MCF-7), some pathogenic microbes, and SARS-CoV-2 viruses was tested. Under the optimized conditions, alginate was extracted from P. pavonica at a rate of 21.13 ± 2.47 % DW, S. cinereum at 24.08 ± 0.33 % DW g/L, T. turbinata at 17.47 ± 0.26 % DW, and D. dichotoma at a rate of 19.57 ± 3.60 % DW. The alginate extracted from D. dichotoma showed the highest antioxidant, anticancer, and antiviral activity.

Hydrogel-based platforms for site-specific doxorubicin release in cancer therapy

Hydrogels are promising candidates for the delivery of therapeutics in the treatment of human cancers. Regarding to the biocomaptiiblity, high drug and encapsulation efficacy and adjustable physico-chemical features, the hydrogels have been widely utilized for the delivery of chemotherapy drugs. Doxorubicin (DOX) is one of the most common chemotherapy drugs used in cancer therapy through impairing topoisomerase II function and increasing oxidative damage. However, the tumor cells have developed resistance into DOX-mediated cytotoxic impacts, requiring the delivery systems to increase internalization and anti-cancer activity of this drug. The hydrogels can deliver DOX in a sustained manner to maximize its anti-cancer activity, improving cancer elimination and reduction in side effects and drug resistance. The natural-based hydrogels such as chitosan, alginate and gelatin hydrogels have shown favourable biocompatibility and degradability in DOX delivery for tumor suppression. The hydrogels are able to co-deliver DOX with other drugs or genes to enhance drug sensitivity and mediate polychemotherapy, synergistically suppressing cancer progression. The incorporation of nanoparticles in the structure of hydrogels can improve the sustained release of DOX and enhancing intracellular internalization, accelerating DOX's cytotoxicity. Furthermore, the stimuli-responsive hydrogels including pH-, redox- and thermo-sensitive platforms are able to improve the specific release of DOX at the tumor site. The DOX-loaded hydrogels can be further employed in the clinic for the treatment of cancer patients and improving efficacy of chemotherapy.

A Study on the Potential of Valorizing Sargassum latifolium into Biofuels and Sustainable Value-Added Products

To increase the limited commercial utility and lessen the negative environmental effects of the massive growth of brown macroalgae, this work illustrates the feasibility of valorizing the invasively proliferated Sargassum latifolium into different value-added products. The proximate analysis recommends its applicability as a solid biofuel with a sufficient calorific value (14.82 ± 0.5 MJ/kg). It contains 6.00 ± 0.07% N + P2O5 + K2O and 29.61 ± 0.05% organic C. Its nutritional analysis proved notable carbohydrate, ash, protein, and fiber contents with a rational amount of lipid and a considerable amount of beneficial macronutrients and micronutrients, with a low concentration of undesirable heavy metals. That recommends its application in the organic fertilizer, food, medicine, and animal fodder industries. A proposed eco-friendly sequential integrated process valorized its biomass into 77.6 ± 0.5 mg/g chlorophyll, 180 ± 0.5 mg/g carotenoids, 5.86 ± 0.5 mg/g fucoxanthin, 0.93 ± 0.5 mg/g β-carotene, 21.97 ± 0.5% (w/w) alginate, and 16.40 ± 0.5% (w/w) cellulose, with different industrial and bioprocess applications. Furthermore, Aspergillus galapagensis SBWF1, Mucor hiemalis SBWF2, and Penicillium oxalicum SBWF3 (GenBank accession numbers OR636487, OR636488, and OR636489) have been isolated from its fresh biomass. Those showed wide versatility for hydrolyzing and saccharifying its polysaccharides. A Gram-negative Stutzerimonas stutzeri SBB1(GenBank accession number OR764547) has also been isolated with good capabilities to ferment the produced pentoses, hexoses, and mannitol from the fungal saccharification, yielding 0.25 ± 0.014, 0.26 ± 0.018, and 0.37 ± 0.020 g ethanol/g algal biomass, respectively. Furthermore, in a pioneering step for valuing the suggested sequential biomass hydrolysis and bioethanol fermentation processes, the spent waste S. latifolium disposed of from the saccharification process has been valorized into C-dots with potent biocidal activity against pathogenic microorganisms.

Seaweed-based biopolymers for food packaging: A sustainable approach for a cleaner tomorrow

With the increasing environmental and health consequences of uncontrolled plastic use, the scientific community is progressively gravitating toward biodegradable and ecofriendly packaging alternatives. Seaweed polysaccharides have attracted attention recently because of their biodegradability, nontoxicity, antioxidant properties, and superior film-forming ability. However, it has some limitations for packaging applications, such as low tensile strength, water solubility, and only modest antimicrobial properties. The incorporation of biopolymers, nanoparticles, or organic active ingredients enhances these characteristics. This review encapsulates the contemporary research landscape pivoting around the role of seaweed polysaccharides in the development of bioplastics, active packaging solutions, edible films, and protective coatings. A meticulous collation of existing literature dissects the myriad food application avenues for these marine biopolymers, emphasizing their multifaceted physical, mechanical, thermal, and functional attributes, including antimicrobial and antioxidant. A key facet of this review spotlights environmental ramifications by focusing on their biodegradability, reinforcing their potential as a beacon of sustainable innovation. This article delves into the prevalent challenges that stymie large-scale adoption and commercialization of seaweed-centric packaging, offering a comprehensive perspective on this burgeoning domain.

A Review on Hydrophobically Associated Alginates: Approaches and Applications

Alginates are linear anionic polysaccharides, which are well-known for their biocompatible, nontoxic, and biodegradable nature. The polymer consists of alternating units of β-(1 → 4)-linked D-mannuronic acid (M) and α-(1 → 4)-linked L-guluronic acid (G) that have hydroxyl and carboxyl groups as the main functional groups. As a large number of free carboxyl and hydroxyl groups are present in the polymeric chain, the polymer is predominantly hydrophilic. The food and pharmaceutical industries have been the most extensive utilizers of alginates to produce gelling and thickening agents. However, by imparting hydrophobicity to alginates, the range of applications can be widened. Although there are reviews on alginate and its chemical modifications, reviews focusing on hydrophobically associated alginates have not been presented. The commonly used chemical modifications to incorporate hydrophobicity include esterification, Ugi reaction, reductive amination, and graft copolymerization. The hydrophobically modified alginates play an important role in delivery of hydrophobic drugs and pesticides as the modification increases the affinity toward hydrophobic components and helps in their sustained release. Due to their nontoxic and edible nature, they find use in the food industry as emulsion stabilizer to stabilize oil-in-water emulsions and to improve creaming ability. Further, alginate-based materials such as membranes, aerogels, and films are hydrophobically modified to improve their functionality and applicability to water treatment and food packaging. This Review aims to highlight the important chemical modifications and methods that are done to impart hydrophobicity to alginate, and the applications of hydrophobically modified alginates in different sectors ranging from drug delivery to food packaging are discussed.

Preparation and potential antitumor activity of alginate oligosaccharides degraded by alginate lyase from Cobetia marina

It is of great significance to develop marine resources and study its potential biological activity by using alginate lyase produced by marine psychrophilic bacteria. In the previous study, a new marine psychrophilic bacterium (Cobetia marina HQZ08) was screened from the growth area of Laminaria japonica, and it was found that the strain could efficiently produce alginate-degrading enzyme (Aly30). In this paper, the ability of Aly30 to degrade alginate was optimized and the optimal degradation conditions were obtained. It was found that the main degradation product of alginate oligosaccharides was trisaccharide. In vitro cell experiments showed that the antitumor activity of low molecular weight alginate oligosaccharides was better than that of high molecular weight alginate oligosaccharides. In summary, Aly30 had the potential to produce alginate oligosaccharides with low degree of polymerization and antitumor activity, which provided a reference for the enzymatic preparation and application of alginate oligosaccharides.

Seaweed-based alginate/hydroxyapatite composite for the effective removal of bacteria, cyanobacteria, algae, and crystal violet from water

A novel cost-effective and multifunctional nanocomposite was developed based on sustainable macroalgae biomass. The brown seaweed Sargassum latifolium was utilized for alginate extraction and the calcareous red seaweed Tricleocarpa fragilis was utilized as CaCO3 source for nanohydroxyapatite synthesis. The developed Zn2+-crosslinked alginate/nanohydroxyapatite (ZA/nHA) beads were characterized by FT-IR, XRD, and TEM. The antimicrobial potential of ZA/nHA to disinfect synthetic Escherichia coli-contaminated water was evaluated at different bacterial load and composite concentrations. The developed ZA/nHA effectively inactivated bacteria at initial concentration ≤ 105 CFU mL-1 and 0.5-1% (w/v) of ZA/nHA within 300-360 min. The kinetics of bacterial disinfection exhibited better fitting to Weibull model than Log-liner model, which confirmed the disinfection process. Furthermore, treatment of the cyanobacterium (Chroococcus sp.) and the microalga (Chlorella sp.) with ZA/nHA showed promising antialgal properties as indicated by reductions in chlorophyll a. The treatment indicated 100% and 90% removal of Chroococcus sp. and Chlorella sp. within 2 and 4 days, respectively. The developed ZA/nHA also exhibited a promising application as a biosorbent for crystal violet (CV). The adsorption process was very fast (0.171 mg CV g-1 adsorbent was removed within 7 min at pH 6.0). The adsorption kinetics exhibited better fitting to the pseudo-second order and Elovich models than the pseudo-first order equation. Besides, Sips model better represented the isotherm data of CV adsorption. The thermodynamic analysis indicated exothermic adsorption, which became more favorable at low temperature and high CV concentration. The developed nanocomposite is eco-friendly and suitable for multiple environmental applications.

Sargassum macroalgae from Quintana Roo as raw material for the preparation of high-performance phosphate adsorbent from aqueous solutions

Currently, the large volumes of Sargassum biomass (Sgs) arriving on Caribbean coasts are a problem that must be solved quickly. One alternative is to obtain value-added products from Sgs. In this work, Sgs is demonstrated to be a high-performance Ca - bioadsorbent for phosphate removal by a heat pretreatment at 800 °C that produces biochar. According to XRD analysis, calcined Sgs (CSgs) have a composition of 43.68%, 40.51%, and 8.69% of Ca(OH)2, CaCO3, and CaO, making CSgs a promising material for phosphate removal and recovery. Results demonstrated that CSgs have a high capacity to adsorb P over a wide range of concentrations (25-1000 mg P/L). After P removal, at low P concentration, the adsorbent material is rich in apatite (Ca5(PO4)3OH), and at high P concentration, brushite (CaHPO4•2H2O) was the main P compound. The CSg reached a Qmax of 224.58 mg P/g, which is higher than other high-performance adsorbents reported in the literature. The phosphate adsorption mechanism was dominated by chemisorption, followed by precipitation according to the pseudo-second-order kinetic model. The solubility of P (74.5 wt%) in formic acid solution and the water-soluble P (24.8 wt%) for CSgs after P adsorption indicated that the final product presents the potential to be used as fertilizer for acid soils. This biomass's processability and high phosphate adsorption performance for P removal make CSgs a potential material for wastewater treatment, and subsequent use of these residues as fertilizer offers a circular economy solution to this problem.

Microwave Assisted Extraction of Raw Alginate as a Sustainable and Cost-Effective Method to Treat Beach-Accumulated Sargassum Algae

This paper highlights the potential of Sargassum algae, recovered from raw beach seaweed wastes, as a valid source of valuable sodium alginate. Alginate is a biodegradable, highly attractive polysaccharide widely used in food, pharmaceuticals, and biomedicine applications. The aim of this work is to employ a new eco-sustainable and cost-effective extractive method to obtain alginate as a raw material from pollutant organic Sargassum seaweeds. Algae were exposed to microwave pre-treatment under static and dynamic conditions, and three different extractive protocols were followed: (a) conventional, (b) hot water and (c) alkaline method. All samples were characterized by GPC, SEM, FTIR/ATR and TGA. It was found that alginate's best performances were obtained by the microwave dynamic pre-treatment method followed by alkaline extractive protocol. Nevertheless, the microwave pre-treatment of algae allowed the easiest breaking of their cell walls and the following fast releasing of sodium alginate. The authors demonstrated that microwave-enhanced extraction is an effective way to obtain sodium alginate from Sargassum-stranded seaweed waste materials in a cost-effective and eco-sustainable approach. They also assessed their applications as mulching films for agricultural applications.

Physicochemical and functional characterization of gelatin edible film incorporated with fucoidan isolated from Sargassum tenerrimum

Biodegradable films were created with fish gelatin and fucoidan extracted from Sargassum tenerrimum using 30% glycerol as a plasticizer. The gelatin films were incorporated with fucoidan (2.5%, 5%, 7.5%, and 10%), respectively. Results presented that the average thickness of films ranged from 0.12 to 0.147 mm. Tensile strength (TS) was decreased from 29.27 to 3.46 MPa by adding the fucoidan except for the gelatin/fucoidan 10% (5.35 MPa) sample. The results showed that the physical characteristics (the contact angle (Ɵ), water solubility, opacity, and moisture content) of the films significantly changed depending on different fucoidan concentrations. FTIR and SEM analysis confirmed the interaction of fucoidan with gelatin in the composite film. Furthermore, adding 10% fucoidan showed high DPPH radical scavenging activity (65%) than other treatments. Therefore, incorporation of fucoidan extracted from brown algae (Sargassum tenerrimum) with fish gelatin films improved thermal stability, anti-oxidative, and antibacterial characteristics in addition to enhanced mechanical and protective properties, to be used as a bioactive edible film in the food packaging industry.

Microwave-Assisted Hydrothermal Processing of Rugulopteryx okamurae

One possible scheme of Rugulopteryx okamurae biomass valorization based on a green, rapid and efficient fractionation technique was proposed. Microwave-assisted pressurized hot water extraction was the technology selected as the initial stage for the solubilization of different seaweed components. Operation at 180 °C for 10 min with a 30 liquid-to-solid ratio solubilized more than 40% of the initial material. Both the alginate recovery yield (3.2%) and the phenolic content of the water-soluble extracts (2.3%) were slightly higher when distilled water was used as solvent. However, the carbohydrate content in the extract (60%) was similar for both solvents, but the sulfate content was higher for samples processed with salt water collected from the same coast as the seaweeds. The antiradical capacity of the extracts was related to the phenolic content in the extracts, but the cytotoxicity towards HeLa229 cancer cells was highest (EC50 = 48 µg/mL) for the extract obtained with distilled water at the lowest temperature evaluated. Operation time showed a relevant enhancement of the extraction performance and bioactive properties of the soluble extracts. The further fractionation and study of this extract would be recommended to extend its potential applications. However, due to the low extraction yield, emphasis was given to the solid residue, which showed a heating value in the range 16,102-18,413 kJ/kg and could be useful for the preparation of biomaterials according to its rheological properties.

Recent advances in the production, properties and applications of alginate oligosaccharides - a mini review

Alginate oligosaccharides (AOS) made from the degradation of alginate, to some extent, makes up for the poor solubility and bioavailability of alginate as a macromolecular substance and possess several beneficial biological activities that are absent in alginate. These properties include prebiotic, glycolipid regulatory, immunomodulatory, antimicrobial, antioxidant, anti-tumor, promoting plant growth and other activities. Consequently, AOS has significant potential for use in the agricultural, biomedical, and food industries, and has been the focus of research in the field of marine biological resources. This review comprehensively covers methods (physical, chemical, and enzymatic methods) for the production of AOS from alginate. More importantly, this paper reviews recent advances in the biological activity and potentially industrial and therapeutic applications of AOS, providing a reference for future research and applications of AOS.

Macroalgal-derived alginate/wastepaper hydrogel to alleviate sunflower drought stress

MAIN CONCLUSION

Alginate/wastepaper hydrogel mitigated sunflower drought stress by increasing the water holding capacity of the soil and decreasing phosphate leaching. The hydrogel promoted sunflower growth and decreased stress related biomarkers. There is a growing interest in the development of biodegradable hydrogels for the alleviation of drought stress on plants. A novel hydrogel based on brown algal-derived alginate and wastepaper was developed and tested as a soil supplement for sunflower growth under moderate (75% field capacity (FC)) and extreme (50% FC) water-deficit stress. The hydrogel showed fast swelling in water, which obeyed the pseudo-first order kinetics. Besides, it increased the water holding capacity of the soil and exhibited a good phosphate adsorption (37 mg PO₄^- g^-1 hydrogel after 6 days) in the soil, and more than 67% of the adsorbed phosphate was desorbed after 20 days. Thus, the phosphate leaching from the hydrogel-amended soil in a column experiment was only 2.77 mg after 4 times of over-irrigation, compared to 11.91 mg without the hydrogel. The hydrogel application promoted various root traits such as fresh and dry biomass, area, and length by > 2-, > 1.6-, > 1.35-, and > 1.3-folds under both water regimes in relation to the no-hydrogel treatments at the same conditions. Furthermore, the sunflower shoots exhibited similar proline contents to the well-watered control (100% FC), with > 50% reduction in relation to the drought-stressed plants under the same conditions. Similarly, the malondialdehyde contents were lowered by > 15%. The analysis of the antioxidant enzymes also indicated a marked reduction in the specific activities of catalase and ascorbate peroxidase under both 75 and 50% FC compared to the respective controls. Additionally, the hydrogel promoted the uptake of phosphate by sunflower roots. These results implied that the developed biodegradable hydrogel could be effectively applied as a soil additive to alleviate drought stress on crops.

Environmentally benign alginate extraction and fibres spinning from different European Brown algae species

Applications of natural fibres are expanding, and sustainable alternatives are needed to support this growing demand. We investigated the production of fibres using alginates from Saccharina latissima (SAC), Laminaria digitata (LAM), Sacchoriza polyschides (SACC), and Himanthalia spp. (HIM). After extraction (3 % w/v biomass) using a sustainable protocol based on citric acid, crude alginate represented 61-65 % of the biomass dry weight for SAC and LAM, and 34-41 % for SACC and HIM when experiments were performed at small scale (1.5 g of starting material). Interestingly, scaling-up extraction (60 g of starting material) decreased yields to 26-30 %. SAC and LAM alginates had the highest M/G (mannuronic acid/guluronic acid) ratios and molecular weights when compared to those from SACC and HIM (M/G:1.98 and 2.23, MW: 302 and 362 kDa, vs 1.83 and 1.86, 268 and 168 kDa). When the four types of alginates were tested for spinning fibres cross-linked with CaCl2, only SAC and LAM alginates produced fibres. These fibres showed no clumps or cracks under stretching action and presented a similar Young's modulus (2.4 and 2.0 GPa). We have demonstrated that alginate extracted from S. latissima and L. digitata can be successfully spun into functional fibres cross-linked with CaCl2.

Ultrasound-assisted extraction of alginic acid from Sargassum angustifolium harvested from Persian Gulf shores using response surface methodology

In this study, the extraction and characterization of alginic acid, the most abundant compound among brown algae were investigated. The used algae were Sargassum angustifolium from the family of brown algae native to the coasts of the Persian Gulf. The effect of temperature, time, algae mass to solvent volume ratio, and ultrasonic power on the extraction yield and ratio of monomers (M/G) was investigated using the central composite design method. Moreover, the effect of the mentioned parameters on the poly dispersity index and cytotoxic effects against breast cancer cells were also investigated. The maximum obtained extraction yield was 46 %, which was higher than those reported for algae in tropical climates. This shows the effectiveness of ultrasound in facilitating the extraction process. In addition, the minimum monomer ratio was 0.45, the minimum poly dispersity index was 2.5 and the maximum cytotoxicity for using the extract on breast cancer cell line (MCF-7) was 20.3 % (with alginic acid concentration of 250 micrograms per milliliter).

Development of sodium alginate-based antioxidant and antibacterial bioactive films added with IRMOF-3/Carvacrol

The purpose of this study was to compare the effects of different concentrations of the amine-functionalized isoreticular metal-organic framework-3 loaded with carvacrol (IRMOF-3/CA) on the properties of sodium alginate (SA) composite films, thus determining the optimal addition amount and further preparing bioactive packaging film with antibacterial and antioxidant activities. The morphology, structure, physical properties, antioxidant and antibacterial activities of the films were characterized and analyzed. The results showed that the thermal stability and light barrier property of the films were improved by the addition of IRMOF-3/CA. When the additional concentration was 0.4 wt%, the tensile, water vapor barrier and hydrophobic properties of the films were increased by 30.13%, 9.06% and 46.43% respectively compared with those of pure SA film. Moreover, the film added with IRMOF-3/CA had sustained antioxidant and antibacterial activities, and had an apparent fresh-keeping effect on pork, suggesting its application potential in food packaging.

Research Progress on the Protective Effect of Brown Algae-Derived Polysaccharides on Metabolic Diseases and Intestinal Barrier Injury

In the human body, the intestine is the largest digestive and immune organ, where nutrients are digested and absorbed, and this organ plays a key role in host immunity. In recent years, intestinal health issues have gained attention and many studies have shown that oxidative stress, inflammation, intestinal barrier damage, and an imbalance of intestinal microbiota may cause a range of intestinal diseases, as well as other problems. Brown algae polysaccharides, mainly including alginate, fucoidan, and laminaran, are food-derived natural products that have received wide attention from scholars owing to their good biological activity and low toxic side effects. It has been found that brown algae polysaccharides can repair intestinal physical, chemical, immune and biological barrier damage. Principally, this review describes the protective effects and mechanisms of brown algae-derived polysaccharides on intestinal health, as indicated by the ability of polysaccharides to maintain intestinal barrier integrity, inhibit lipid peroxidation-associated damage, and suppress inflammatory cytokines. Furthermore, our review aims to provide new ideas on the prevention and treatment of intestinal diseases and act as a reference for the development of fucoidan as a functional product for intestinal protection.

Alginate industrial waste streams as a promising source of value-added compounds valorization

The alginate industry processes more than hundred thousand tons per year of algae in Europe, discarding around 80% of the algae biomass as different solid/liquid residual streams. In this work, Saccharina latissima and Ascophyllum nodosum, their generated alginates and all residual fractions generated in the process were characterized in terms of lipid, ash, protein content, and the carbohydrate composition and antioxidant capacities analyzed. The first fraction after acid treatment (ca. 50% of the initial dry biomass) was rich in phlorotannins (15 mg GAE/g) and bioactive fucoidans (15-70%), with a high sulfation degree in A. nodosum. Two fractions generated from the solid residue, one soluble and another insoluble (Ra and Rb, respectively), constituted 9% and 5-8% of the initial biomass and showed great potential as a source of soluble protein (30% for S. latissima), and cellulose (70%) or fucoidan, respectively. Valorization strategies are suggested for these waste streams, evidencing their high potential as bioactive, texturizing or nutritional added-value ingredients for cosmetic, food, feed or pharmaceutical applications.

A novel alginate from Sargassum seaweed promotes diabetic wound healing by regulating oxidative stress and angiogenesis

Diabetic skin ulcer is one of the most severe complications in diabetes, however, current therapeutic approaches are not effective enough. Agents modulating oxidative stress, inflammation, and angiogenesis are quite promising for alleviation of diabetic skin ulcers. In this study, a novel Sargassum kjellmanianum-derived polysaccharide (SARP) was prepared. SARP was an alginate with Mw of 45.4 kDa, consisting of 76.56% mannuronic acid, 18.89% guluronic acid, and 4.55% glucuronic acid. SARP could attenuate oxidative stress-induced cell damage via activating nuclear factor erythroid 2-related factor 2 (Nrf2). SARP also promoted the migration and tube formation of HUVECs, which was related to the increased vascular endothelial growth factor (VEGF) expression. In diabetic wound model, SARP (iv, 200 mg/kg) administration increased angiogenesis, alleviated oxidative stress, ameliorated diabetes-related aberrations, and thereby accelerated diabetic wound healing. These findings identified SARP had potential to be developed as a drug candidate for diabetic skin ulcers.

Alginate-based Composites Microspheres: Preparations and Applications for Bone Tissue Engineering

Alginate-based biomaterials have been extensively studied for bone tissue engineering. Scaffolds, microspheres, and hydrogels can be developed using alginate, which is biocompatible, biodegradable, and able to deliver growth factors and drugs. Alginate microspheres can be produced using crosslinking, microfluidic, three-dimensional printing, extrusion, and emulsion methods. The sizes of the alginate microspheres range from 10 µm to 4 mm. This review describes the chemical characterization and mechanical assessment of alginate-based microspheres. Combinations of alginate with hydroxyapatite, chitosan, collagen, polylactic acid, polycaprolactone, and bioglass were discussed for bone tissue repair and regeneration. In addition, alginate combinations with bone morphogenetic proteins, vascular endothelial growth factor, transforming growth factor beta-3, other growth factors, cells, proteins, drugs, and osteoinductive drugs were analyzed for tissue engineering applications. Furthermore, the biocompatibility of developed alginate microspheres was discussed for different cell lines. Finally, alginate microsphere-based composites with stem cell interaction for bone tissue regeneration were presented. In the present review, we have assessed the preclinical research on in vivo models of alginate-based microspheres for bone tissue repair and regeneration. Overall, alginate-based microspheres are potential candidates for graft substitutes and the treatment of various bone-related diseases.

Process optimization and modeling of Cd2+ biosorption onto the free and immobilized Turbinaria ornata using Box-Behnken experimental design

The release of effluents containing cadmium ions into aquatic ecosystems is hazardous to humans and marine organisms. In the current investigation, biosorption of Cd2+ ions from aqueous solutions by freely suspended and immobilized Turbinaria ornata biomasses was studied. Compared to free cells (94.34%), the maximum Cd2+ removal efficiency reached 98.65% for immobilized cells obtained via Box-Behnken design under optimized conditions comprising algal doses of 5.04 g L-1 and 4.96 g L-1, pH values of 5.06 and 6.84, and initial cadmium concentrations of 25.2 mg L-1 and 26.19 mg L-1, respectively. Langmuir, Freundlich, and Temkin isotherm models were suitably applied, providing the best suit of data for free and immobilized cells, but the Dubinin-Radushkevich model only matched the immobilized algal biomass. The maximum biosorption capacity of Cd2+ ions increased with the immobilized cells (29.6 mg g-1) compared to free cells (23.9 mg g-1). The Cd2+ biosorption data obtained for both biomasses followed pseudo-second-order and Elovich kinetic models. In addition, the biosorption process is controlled by film diffusion followed by intra-particle diffusion. Cd2+ biosorption onto the free and immobilized biomasses was spontaneous, feasible, and endothermic in nature, according to the determined thermodynamic parameters. The algal biomass was further examined via SEM/EDX and FTIR before and after Cd2+ biosorption. SEM/EDX analysis revealed Cd2+ ion binding onto the algal surface. Additionally, FTIR analysis confirmed the presence of numerous functional groups (hydroxyl, carboxyl, amine, phosphate, etc.) participating in Cd2+ biosorption. This study verified that immobilized algal biomasses constitute a cost-effective and favorable biosorbent material for heavy metal removal from ecosystems.

Injectable and biocompatible alginate-derived porous hydrogels cross-linked by IEDDA click chemistry for reduction-responsive drug release application

In this work, novel injectable and reduction-responsive hydrogels were successfully prepared via inverse electron demand Diels-Alder reaction between alginate-norbornene and a water-soluble PEG based disulfide cross-linker. The reduction-responsive cross-linker was designed to contain a PEG chain within two disulfide linkages, and two terminal tetrazine groups. The resulting hydrogels possessed high swelling ratios, porous morphology, excellent drug loading efficiency (~92%), and suitable mechanical properties. The drug release experiments demonstrated that the hydrogels released more than 90% of the encapsulated doxorubicin (DOX) in the presence of 10 mM glutathione while a minimal DOX release (<25%) was measured in physiological buffer (PBS, pH = 7.4) after 11 d. The cross-linker and hydrogels did not exhibit any apparent cytotoxicity to fibroblast cells. In contrast, DOX-loaded hydrogels induced anti-tumor activity against cancer cells. The injectable and reduction-responsive hydrogels hold great potential as a biomaterial for stimuli responsive drug delivery applications.

Alginate poly and oligosaccharide (AOS) from Sargassum sp. as immunostimulant in gnotobiotic artemia challenge tests and antibacterial diffusion disc assay against pathogenic Vibrio parahaemolyticus, V. vulnificus and V. harveyi

Alginate is a polysaccharide derived from Sargassum sp. and is a potent immunostimulant with antibacterial activity, including against Vibrio spp. This genus of bacteria is found in freshwater and marine environments and is a common infectious, pathogenic bacteria both for aquatic cultivans and humans. Here, we determined the ability of sodium alginate polysaccharides and oligosaccharides (AOS) to act as immunostimulants in Artemia challenge tests and antibacterial diffusion disc assays against Vibrio parahaemolyticus, V. vulnificus, and V. harveyi. The AOS was produced by thermal heating. Dry sodium alginates were weighed out from 4.21 to 6.47 grams with a yield varying from 21.05 to 32.35%. Alginate polysaccharides were challenged against V harveyi and showed 8 positive results. The highest inhibitor zone was 12.962±3.623 mm. Based on 18 tests, AOS showed 12 positive results, with the highest inhibitor zone being 10.250±0.09 mm. The encapsulated alginate against Vibrio parahaemolyticus, Vibrio harveyi, Vibrio vulnificus, and the non-challenged tests without any Vibrio spp. addition resulted in the best concentrations of 800 ppm (polysaccharide) and 600 ppm (oligosaccharide), respectively. The lower concentration of oligosaccharides alginate were more effective and has the potential to be superior as an antibacterial agent and immunestimulant, as opposed to alginate polysaccharide.

Structural and Emulsifying Properties of Soybean Protein Isolate-Sodium Alginate Conjugates under High Hydrostatic Pressure

Soybean protein isolate (SPI) is a kind of plant derived protein with high nutritional value, but it is underutilized due to its structural limitations and poor functionalities. This study aimed to investigate the effects of high hydrostatic pressure (HHP) treatment on SPI and sodium alginate (SA) conjugates prepared through the Maillard reaction. The physicochemical properties of the conjugate synthesized under 200 MPa at 60 °C for 24 h (SPI–SA–200) were compared with those of the conjugate synthesized under atmospheric pressure (SPI–SA–0.1), SPI-SA mixture, and SPI. The HHP (200 MPa) significantly hindered the Maillard reaction. This effect was confirmed by performing SDS-PAGE. The alterations in the secondary structures, such as α-helices, were analyzed using circular dichroism spectroscopy and the fluorescence intensity was determined. Emulsifying activity and stability indices of SPI-SA-200 increased by 33.56% and 31.96% respectively in comparison with the SPI–SA–0.1 conjugate. Furthermore, reduced particle sizes (356.18 nm), enhanced zeta potential (‒40.95 mV), and homogeneous droplet sizes were observed for the SPI-SA-200 emulsion. The present study details a practical method to prepare desirable emulsifiers for food processing by controlling the Maillard reaction and improving the functionality of SPI.

Functional Features of Alginates Recovered from Himanthalia elongata Using Subcritical Water Extraction

Subcritical water extraction of Himanthalia elongata and the subsequent acetone fractionation to precipitate crude fucoidans generated a liquid phase which was used to recover alginates with a wide range of viscoelastic features and other soluble extracts with potential biological activities. The precipitated alginate was converted to sodium alginate using an environmentally friendly treatment before being characterized by Fourier transform infrared attenuated total reflectance, nuclear magnetic resonance, high performance size exclusion chromatography and rheological measurements. The cell viability of three human cell lines (A549, HCT-116, T98G) in the presence of the extracts obtained before and after acetone fractionation was assessed. Fractionation with different acetone volumes showed a slight effect in the behavior of the different tested cell lines. Results also indicated a notable effect of the processing conditions on the block structure and molar mass of the extracted biopolymer, with the subsequent impact on the rheological properties of the corresponding gelled matrices.

Biophysico-Chemical Properties of Alginate Oligomers Obtained by Acid and Oxidation Depolymerization

The aim of the study was to obtain alginate oligosaccharides by using two degradation methods of sodium alginate (SA): with hydrochloric acid (G—guluronate, M—mannuronate and G + M fractions) and hydrogen peroxide (HAS—hydrolyzed SA), in order to assess and compare their biological activity and physico-chemical properties, with an attempt to produce gels from the obtained hydrolysates. The efficiency of each method was determined in order to select the fastest and most efficient process. The ferric ion reducing antioxidant power (FRAP), the ability to scavenge DPPH free radicals, rheological properties, Fourier Transformed Spectroscopy (FTIR) and the microbiological test against Escherichia coli and Staphylococcus aureus were performed. In order to check the functional properties of the obtained oligosaccharides, the texture profile analysis was assessed. The hydrolysis yield of acid SA depolymerization was 28.1% and from hydrogen peroxide SA, depolymerization was 87%. The FTIR analysis confirmed the degradation process by both tested methods in the fingerprint region. The highest ferric reducing antioxidant power was noted for HSA (34.7 µg), and the highest hydroxyl radical scavenging activity was obtained by G fraction (346 µg/Trolox ml). The complete growth inhibition (OD = 0) of alginate hydrolysates was 1%. All tested samples presented pseudoplastic behavior, only HSA presented the ability to form gel.

Valorization of pelagic sargassum biomass into sustainable applications: Current trends and challenges

Since long ago, pelagic Sargassum mats have been known to be abundant in the Sargasso Sea, where they provide habitat to diverse organisms. However, over the last few years, massive amounts of pelagic Sargassum have reached the coast of several countries in the Caribbean and West Africa, causing economic and environmental problems. Aiming for lessening the impacts of the blooms, governments and private companies remove the seaweeds from the shore, but this process results expensive. The valorization of this abundant biomass can render Sargassum tides into an economic opportunity and concurrently solve their associated environmental problems. Despite the diverse fields where algae have found applications and the relevance of this recurrent situation, Sargassum biomass remains without large scale applications. Therefore, this review aims to present the potential uses of these algae, identifying the limitations that must be assessed to effectively valorize this bioresource. Due to the constraints identified for each of the presented applications, it is concluded that a biorefinery approach should be developed to effectively valorize this abundant biomass. However, there is an urgent need for investigations focusing on holopelagic Sargassum to be able to truly valorize this seaweed.

Dynamic cross-linking of an alginate-acrylamide tough hydrogel system: time-resolved in situ mapping of gel self-assembly

Hydrogels are a popular class of biomaterial that are used in a number of commercial applications (e.g.; contact lenses, drug delivery, and prophylactics). Alginate-based tough hydrogel systems, interpenetrated with acrylamide, reportedly form both ionic and covalent cross-links, giving rise to their remarkable mechanical properties. In this work, we explore the nature, onset and extent of such hybrid bonding interactions between the complementary networks in a model double-network alginate-acrylamide system, using a host of characterisation techniques (e.g.; FTIR, Raman, UV-vis, and fluorescence spectroscopies), in a time-resolved manner. Further, due to the similarity of bonding effects across many such complementary, interpenetrating hydrogel networks, the broad bonding interactions and mechanisms observed during gelation in this model system, are thought to be commonly replicated across alginate-based and broader double-network hydrogels, where both physical and chemical bonding effects are present. Analytical techniques followed real-time bond formation, environmental changes and re-organisational processes that occurred. Experiments broadly identified two phases of reaction; phase I where covalent interaction and physical entanglements predominate, and; phase II where ionic cross-linking effects are dominant. Contrary to past reports, ionic cross-linking occurred more favourably via mannuronate blocks of the alginate chain, initially. Evolution of such bonding interactions was also correlated with the developing tensile and compressive properties. These structure-property findings provide mechanistic insights and future synthetic intervention routes to manipulate the chemo-physico-mechanical properties of dynamically-forming tough hydrogel structures according to need (i.e.; durability, biocompatibility, adhesion, etc.), allowing expansion to a broader range of more physically and/or environmentally demanding biomaterials applications.

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications

With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

Multi-response optimization of alginate bleaching technology extracted from brown seaweeds by an eco-friendly agent

Alginate only finds industrial applicability after undergoing a bleaching process to improve its visual appearance. Box-Behnken Design was used to optimize bleaching parameters (time, oxygen flow and temperature) for sodium alginate (SA) extracted from seaweeds using ozone as the bleaching agent. The optimal conditions (oxygen flow 2 L/min for 35 min at 25 °C) resulted in an ozone-bleached SA with a mannuronic/guluronic acids ratio of 0.70, viscosity-average molecular weight of 66.30 kDa and dynamic viscosity of 1.39 mPa.s, aligned to strong and brittle gels formation, which are potentially suitable for hydrogels and bioink application. Results indicated that ozonation caused depolymerization of the SA chain. Colorimetric parameters showed that ozone has a great bleaching efficacy. The bleached sample presented high antioxidant capacity, highlighting that discoloration by ozone might have minimal effects on the bioactive compounds which are valuable ingredients for food-based products.

Alginate extraction from Sargassum seaweed in the Caribbean region: Optimization using response surface methodology

Sargassum valorization has become increasingly important as the Caribbean region continues to struggle with the massive growth of the seaweed and its damaging effects. Sodium alginate extraction is one method where the seaweed biomass can be utilized to produce a useful biopolymer. However, current processing generally giving low yields of inferior quality, making it unattractive for commercialization. This article seeks to optimize the extraction process using a Box-Behnken Response Surface Design combined with multistage extraction to obtain higher product yield and purity, as well as giving insights, for the first time, into the physiochemical properties of the extracted alginate from Sargassum biomass. Optimum conditions were found and confirmed through validation, with a crude yield as high as 28 % after 2 stages and a purity of 92 % for purified alginate samples. Characterization of the bleached alginate through NMR studies validated with FTIR, gave an M/G ratio of 0.45 with a molecular weight of 3.14 × 105 g mol-1 and viscosity of 14.10 cP aligned to high gelling capabilities.

Dietary supplementation of Sargassum latifolium modulates thermo-respiratory response, inflammation, and oxidative stress in bacterial endotoxin-challenged male Barki sheep

Endotoxemia is mainly caused by translocation of bacterial lipopolysaccharides (LPS) into the bloodstream. This in turn enhances systemic inflammation and inappropriate production of reactive oxygen species, leading to oxidative injury of vital internal organs and other dangerous effects that can be life-threatening. Here, we evaluated/compared the modulatory effects of consuming two different doses (2% and 4% of the diet) of brown seaweeds (Sargassum latifolium) for 40 consecutive days on thermo-respiratory response, inflammation, and oxidative stress in Barki male sheep (Ovis aries) challenged twice with bacterial LPS (1.25 μg/kg body weight, injected intravenously on days 28 and 35 of the experimental period). The results showed that the diet containing Sargassum latifolium (especially at 4%) modulated significantly (P < 0.05-0.001) the increase in the thermo-respiratory response (skin and rectal temperatures, and respiration rate) and the obtained systemic inflammation (blood leukocytosis, the elevation in the erythrocyte sedimentation rate, and the increase in serum proinflammatory cytokines and heat shock protein-70 concentrations) in the LPS-challenged sheep. In addition, it improved significantly (P < 0.001, especially at 4%) the total antioxidant capacity of the blood of LPS-challenged sheep by increasing the catalase and superoxide dismutase activities. Moreover, it decreased the blood markers of tissue damage (malondialdehyde concentration and the activities of alanine aminotransferase and lactate dehydrogenase) in the LPS-challenged sheep. In conclusion, the diet containing 4% Sargassum latifolium may have potential impact in protecting the ruminant livestock from the serious effects of endotoxemia through improving the animals' antioxidant defense system and regulating their inflammatory and thermo-respiratory responses.

Equilibrium and Kinetics Studies of Metal Ions Biosorption on Alginate Extracted from Marine Red Algae Biomass (Callithamnion corymbosum sp.)

Biosorption is a viable alternative that can be used to remove heavy metal ions from aqueous effluents, as long as the biosorbent used is cost-effective and efficient. To highlight this aspect in this study, alginate extracted from marine red algae biomass (Callithamnion corymbosum sp.) was used as biosorbent for the removal of Cu(II), Co(II) and Zn(II) ions from aqueous media. Biosorption studies were performed in a batch system, and the biosorptive performances of the alginate were examined as function of initial solution pH, biosorbent dosage, contact time, initial metal ions concentration and temperature. The optimal experimental conditions were found: initial solution pH of 4.4, a biosorbent dose of 2.0 g/L and a temperature of 22 °C, when over 88% of Cu(II), 76% of Co(II) and 81% of Zn(II) are removed by biosorption. The modeling of the obtained experimental data show that the Langmuir isotherm model and pseudo-second kinetic model well describe the biosorption processes of studied metal ions. The maximum biosorption capacity (q_max, mg/g) increases in the order: Cu(II) (64.52 mg/g) > Zn(II) (37.04 mg/g) > Co(II) (18.79 mg/g), while the minimum time required to reach the equilibrium is 60 min. Moreover, the regeneration efficiency of alginate is higher than 97% when a 10⁻¹ N HNO₃ solution is used as desorption agent for the recovery of Cu(II), Co(II) and Zn(II) ions. All these characteristics demonstrate that the alginate extracted from marine algae has promising applications in the decontamination of industrial effluent containing metal ions.

The interaction between sodium alginate and myofibrillar proteins: The rheological and emulsifying properties of their mixture

The interaction between sodium alginate (SA) and turbot myofibrillar proteins (TMP) and the effects of SA concentration (0.1%-0.5%) on the rheological and emulsifying properties of the mixture at neutral pH were investigated. TMP and SA formed complexes through electrostatic repulsion and hydrophobic interaction. The FT-IR analysis indicated that hydrogen bonding was also related to the interaction. With the addition of SA, the electrostatic repulsion between molecules enhanced, which prevented protein aggregation and improved the stability of dispersions. The TMP/SA mixture showed non-Newtonian shear-thinning behavior. The viscosity gradually increased with the increasing SA concentration. TMP and SA formed an interconnected gel-like network structure with a predominant elastic behavior. The strength of network increased due to the strong repulsion between the two biopolymers. Both EAI and ESI of TMP significantly increased after SA addition. The addition of SA reduced droplet size of emulsions. The emulsions also showed pseudoplastic behavior. Addition of SA increased stability of emulsions by increasing viscosity of continuous phase. Complexation with SA effectively improved the rheological and emulsifying properties of fish myofibrillar proteins. These results contributed to the efficient utilization of marine fish proteins as functional ingredients in food products.

Use of algal biorefinery waste and waste office paper in the development of xerogels: A low cost and eco-friendly biosorbent for the effective removal of congo red and Fe (II) from aqueous solutions

The present study investigated the use of algae biorefinery waste and wastepaper in the preparation of cost-effective and eco-friendly xerogels for the removal of congo red (CR) and Fe²⁺. The xerogel properties such as density, swelling degree and porosity were modified by incorporating alginate extracted from the brown seaweed Cystoseira trinodis. The developed biosorbents exhibited a light and porous network structure and were characterized by a fast uptake of CR and Fe²⁺ and adsorption efficiency was increased at pH 6-8. The equilibrium adsorption capacity was found to be 6.20-7.28 mg CR g^-1 biosorbent and 8.08-8.39 mg Fe²⁺ g^-1 biosorbent using different xerogels. The adsorption of CR obeyed first-order kinetics, while, Fe²⁺ followed second-order kinetics. Intraparticle diffusion model suggested a boundary layer effect. The adsorption capacity was maximally obtained as 41.15 mg g^-1 and 169.49 mg g^-1 for CR and Fe²⁺ using wastepaper/Spirulina and wastepaper/alginate/Spirulina xerogel, respectively. Temkin isotherm fitted better to the equilibrium data of CR adsorption than Langmuir and Freundlich models. While, equilibrium data of Fe²⁺ exhibited a best fit to both Langmuir and Freundlich models. Additionally, the Dubinin-Radushkevich isotherm suggested that adsorption mechanism of CR or Fe²⁺ is predominately physisorption. Investigation of thermodynamic parameters such as ΔH° and ΔS° and ΔG° confirmed the feasibility, spontaneity, randomness and endothermic nature of the adsorption process. Electrostatic attraction, H-bonding and n-π interactions were mainly involved in the biosorption process of CR. The results of this study showed that the developed xerogels could be effectively applied for dye and heavy metal removal at low concentrations.