Alginate, which is mainly produced by brown algae and decomposed by heterotrophic bacteria, is an important marine organic carbon source. The genus
contains diverse forms of heterotrophic bacteria ...that are widely distributed in marine environments and are an important group in alginate degradation. In this review, the diversity of alginate-degrading
is introduced, and the characteristics of
alginate lyases, including their sequences, enzymatic properties, structures, and catalytic mechanisms, and the synergistic effect of
alginate lyases on alginate degradation are introduced. The acquisition of the alginate degradation capacity and the alginate utilization pathways of
are also introduced. This paper provides a comprehensive overview of alginate degradation by
which will contribute to the understanding of the degradation and recycling of marine algal polysaccharides driven by marine bacteria.
Alginate, a polymer mainly derived from seaweed, has garnered significant attention owing to its renewability, biocompatibility, biodegradability, and exceptional gel formation characteristics, ...rendering it highly versatile for numerous applications. Recognizing the imperative for tailored bulk materials, this review scrutinizes the processing methodologies of alginate-based bulk materials and delineates strategies to improve their properties, encompassing ionic crosslinking, plasticization, and hybridization with other polymers and/or fillers. It explores noteworthy alginate-based blends with natural polymers like polysaccharides and proteins, alongside fossil-based polymers like poly(vinyl alcohol). It also examines alginate-based composites incorporating various nanofillers such as cellulose nanoparticles, graphene, and nanoclays. The processing techniques for these multiphase alginate-based systems encompass solution casting, coating, spinning, 3D printing, and thermomechanical processing. Strategies for crosslinking alginate, plasticizing it, and optimizing its interactions with other polymers/fillers are outlined, bearing repercussions on the resultant materials properties. This review emphasizes the structure–process–property relationships of these multiphase systems in bulk and highlights synergistic effects and potential impediments to property improvements. It surveys prospective applications for alginate-based multiphasic bulk materials, spanning membrane separation, controlled release, wound healing, tissue engineering, food packaging, and agricultural domains. Finally in this field, knowledge gaps have been identified and future research directions are suggested.
Abstract Alginate hydrogels are well-characterized, biologically inert materials that are used in many biomedical applications for the delivery of drugs, proteins, and cells. Unfortunately, canonical ...covalently crosslinked alginate hydrogels are formed using chemical strategies that can be biologically harmful due to their lack of chemoselectivity. In this work we introduce tetrazine and norbornene groups to alginate polymer chains and subsequently form covalently crosslinked click alginate hydrogels capable of encapsulating cells without damaging them. The rapid, bioorthogonal, and specific click reaction is irreversible and allows for easy incorporation of cells with high post-encapsulation viability. The swelling and mechanical properties of the click alginate hydrogel can be tuned via the total polymer concentration and the stoichiometric ratio of the complementary click functional groups. The click alginate hydrogel can be modified after gelation to display cell adhesion peptides for 2D cell culture using thiol-ene chemistry. Furthermore, click alginate hydrogels are minimally inflammatory, maintain structural integrity over several months, and reject cell infiltration when injected subcutaneously in mice. Click alginate hydrogels combine the numerous benefits of alginate hydrogels with powerful bioorthogonal click chemistry for use in tissue engineering applications involving the stable encapsulation or delivery of cells or bioactive molecules.
A 3D printable and highly stretchable tough hydrogel is developed by combining poly(ethylene glycol) and sodium alginate, which synergize to form a hydrogel tougher than natural cartilage. ...Encapsulated cells maintain high viability over a 7 d culture period and are highly deformed together with the hydrogel. By adding biocompatible nanoclay, the tough hydrogel is 3D printed in various shapes without requiring support material.
Alginate denotes a group of industrially important 1-4-linked biopolymers composed of the C-5-epimers β-D-mannuronic acid (M) and α-L-guluronic acid (G). The polysaccharide is manufactured from brown ...algae where it constitutes the main structural cell wall polymer. The physical properties of a given alginate molecule, e.g., gel-strength, water-binding capacity, viscosity and biocompatibility, are determined by polymer length, the relative amount and distribution of G residues and the acetyl content, all of which are controlled by alginate modifying enzymes. Alginate has also been isolated from some bacteria belonging to the genera Pseudomonas and Azotobacter, and bacterially synthesized alginate may be O-acetylated at O-2 and/or O-3. Initially, alginate is synthesized as polymannuronic acid, and some M residues are subsequently epimerized to G residues. In bacteria a mannuronan C-5-epimerase (AlgG) and an alginate acetylase (AlgX) are integral parts of the protein complex necessary for alginate polymerization and export. All alginate-producing bacteria use periplasmic alginate lyases to remove alginate molecules aberrantly released to the periplasm. Alginate lyases are also produced by organisms that utilize alginate as carbon source. Most alginate-producing organisms encode more than one mannuronan C-5 epimerase, each introducing its specific pattern of G residues. Acetylation protects against further epimerization and from most alginate lyases. An enzyme from Pseudomonas syringae with alginate deacetylase activity has been reported. Functional and structural studies reveal that alginate lyases and epimerases have related enzyme mechanisms and catalytic sites. Alginate lyases are now utilized as tools for alginate characterization. Secreted epimerases have been shown to function well in vitro, and have been engineered further in order to obtain enzymes that can provide alginates with new and desired properties for use in medical and pharmaceutical applications.
•Alginate lyase is covalently immobilized on Fe3O4 nanoparticles.•Stability and moderate reusability of immobilized alginate lyase are enhanced.•Immobilized alginate lyase efficiently produces ...alginate oligosaccharides.•Alginate oligosaccharides show potent antioxidant effect in H2O2-stressed HUVECs.•Alginate oligosaccharides inhibit apoptosis in H2O2-stressed HUVECs.
Alginate is a natural polysaccharide resource abundant in brown algae and it can be cleaved into alginate oligosaccharides by alginate lyase. Alginate lyases and the bioactive alginate oligosaccharides have been applied in diverse fields such as pharmaceutical therapy and nutraceutical supplementation. Immobilized enzymes greatly facilitate their industrial application owing to their reusability, stability, and tunability. In this study, magnetic Fe3O4 nanoparticles were synthesized and used to immobilize an exolytic alginate lyase AlgL17 that was characterized previously. The immobilized AlgL17 demonstrated enhanced thermal and pH tolerance, extended storage stability, and moderate reusability. The mass spectrum indicated the specific activity of the immobilized AlgL17 to release alginate oligosaccharides (AOS) from alginate polysaccharide. The produced AOS exhibited their antioxidant and antiapoptotic activities in H2O2-stressed human umbilical vein endothelial cells by upregulation of reactive oxygen species scavenging activities and attenuation of the caspase-mediated apoptosis pathway.
Alginate is a biopolymer used extensively in the food, pharmaceutical, and chemical industries. Alginate oligosaccharides (AOS) derived from alginate exhibit superior biological activities and ...therapeutic potential. Alginate lyases with characteristic substrate specificity can facilitate the production of a broad array of AOS with precise structure and functionality. By adopting innovative analytical tools in conjunction with focused clinical studies, the structure-bioactivity relationship of a number of AOS has been brought to light. This review covers fundamental aspects and recent developments in AOS research. Enzymatic and microbial processes involved in AOS production from brown algae and sequential steps involved in AOS structure elucidation are outlined. Biological mechanisms underlying the health benefits of AOS and their potential industrial and therapeutic applications are elaborated. Withal, various challenges in AOS research are traced out, and future directions, specifically on recombinant systems for AOS preparation, are delineated to further widen the horizon of these exceptional oligosaccharides.
•Alginate oligosaccharides (AOS; DP 2 to 25) exhibit diverse biological activities.•Endolytic alginate lyases are used to prepare AOS with defined structure and function.•Advanced analytical tools are required for in-depth AOS structure analysis.•Exolytic lyases are currently recognized as important tools in AOS sequencing.•Recombinant in vivo production of AOS is desirable to obtain highly pure end products.
Stem cell implantation strategy has exhibited potential to treat the myocardial infarction (MI), however, the low retention and survival limit their applications due to the reactive oxygen species ...(ROS) microenvironment after MI. In this study, the fullerenol nanoparticles are introduced into alginate hydrogel to create an injectable cell delivery vehicle with antioxidant activity. Results suggest that the prepared hydrogels exhibit excellent injectable and mechanical strength. In addition, the fullerenol/alginate hydrogel can effectively scavenge the superoxide anion and hydroxyl radicals. Based on these results, the biological behaviors of brown adipose-derived stem cells (BADSCs) seeded in fullerenol/alginate hydrogel were investigated in the presence of H2O2. Results suggest that the fullerenol/alginate hydrogels have no cytotoxicity effects on BADSCs. Moreover, they can suppress the oxidative stress damage of BADSCs and improve their survival capacity under ROS microenvironment via activating the ERK and p38 pathways while inhibiting JNK pathway. Further, the addition of fullerenol can improve the cardiomyogenic differentiation of BADSCs even under ROS microenvironment. To assess its therapeutic effects in vivo, the fullerenol/alginate hydrogel loaded with BADSCs were implanted in the MI area in rats. Results suggest that the fullerenol/alginate hydrogel can effectively decrease ROS level in MI zone, improve the retention and survival of implanted BADSCs, and induce angiogenesis, which in turn promote cardiac functional recovery. Therefore, the fullerenol/alginate hydrogel can act as injectable cell delivery vehicles for cardiac repair.
The cell wall of brown algae contains alginate as a major constituent. This anionic polymer is a composite of β-d-mannuronate (M) and α-l-guluronate (G). Alginate can be degraded into ...oligosaccharides; both the polymer and its products exhibit antioxidative, antimicrobial, and immunomodulatory activities and, hence, find many commercial applications. Alginate is attacked by various enzymes, collectively termed alginate lyases, that degrade glycosidic bonds through β-elimination. Considering the abundance of brown algae in marine ecosystems, alginate is an important source of nutrients for marine organisms, and therefore, alginate lyases play a significant role in marine carbon recycling. Various marine microorganisms, particularly those that thrive in association with brown algae, have been reported as producers of alginate lyases. Conceivably, the marine-derived alginate lyases demonstrate salt tolerance, and many are activated in the presence of salts and, therefore, find applications in the food industry. Therefore, this review summarizes the structural and biochemical features of marine bacterial alginate lyases along with their applications. This comprehensive information can aid in the expansion of future prospects of alginate lyases.
PDF
