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Brown macroalgae have attracted great attention as an alternative feedstock for biorefining. Although direct conversion of ethanol from alginates (major components of brown macroalgae cell walls) is not amenable for industrial production, significant progress has been made not only on enzymes involved in alginate degradation, but also on metabolic pathways for biorefining at the laboratory level. In this article, we summarise recent advances on four aspects: alginate, alginate lyases, different alginate-degrading systems, and application of alginate lyases and associated pathways. This knowledge will likely inspire sustainable solutions for further application of both alginate lyases and their associated pathways.

Gastroesophageal reflux disease (GERD) is a prevalent global condition, affecting 18.1–27.8% of North Americans and 6.3–18.3% of the Thai population. While proton pump inhibitors (PPIs) are the first-line treatment, only about one-third of patients achieve adequate symptom control. Alginate-based medications in combination with PPIs have shown promise, but the comparative effectiveness of generic versus original alginates remains unexplored. To compare the effectiveness of generic alginate (ONE GERD) versus original alginate (Gaviscon Dual Action Suspension) in combination with PPIs for treating GERD symptoms in patients who failed standard PPI therapy.This multicenter prospective randomized controlled non-inferiority trial included 48 patients who failed standard-dose PPI treatment. Patients were randomized to receive either generic or original alginate four times daily for 28 days. Treatment response was evaluated using the Reflux Disease Questionnaire (RDQ) at days 7 and 28. At day 7, both groups showed identical response rates of 45.83%. By day 28, response rates increased to 54.17% for generic alginate and 70.83% for original alginate ( p  = 0.23). Total RDQ scores and symptom-free rates showed no significant differences between groups at both time points. Adverse event rates were comparable (16.67% vs. 8.33%, p  = 0.66). Analysis of specific symptoms (heartburn, chest pain, and regurgitation) revealed similar improvements in both groups throughout the study period. This study provides evidence supporting the therapeutic equivalence of the generic alginate (ONE GERD) to the original formulation (Gaviscon Dual Action Suspension) in treating symptoms for patients with GERD who have failed PPI therapy. Crucially, the comparable efficacy and safety, coupled with the inherent lower cost of generic medications, suggest significant economic benefits and the potential for wider patient access to effective GERD management. This makes generic alginate a viable and attractive alternative in clinical practice, particularly in resource-limited settings or for patients facing financial constraints, thereby contributing to more equitable healthcare solutions without compromising therapeutic outcomes.

Alginate is a hydrocolloid from algae, specifically brown algae, which is a group that includes many of the seaweeds, like kelps and an extracellular polymer of some bacteria. Sodium alginate is one of the best-known members of the hydrogel group. The hydrogel is a water-swollen and cross-linked polymeric network produced by the simple reaction of one or more monomers. It has a linear (unbranched) structure based on d-mannuronic and l-guluronic acids. The placement of these monomers depending on the source of its production is alternating, sequential and random. The same arrangement of monomers can affect the physical and chemical properties of this polysaccharide. This polyuronide has a wide range of applications in various industries including the food industry, medicine, tissue engineering, wastewater treatment, the pharmaceutical industry and fuel. It is generally recognized as safe when used in accordance with good manufacturing or feeding practice. This review discusses its application in addition to its structural, physical, and chemical properties.

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.

In this study, we identified AlgVR7, a novel bifunctional alginate lyase from Vibrio rumoiensis and characterized its biochemical properties and substrate specificity. Sequence alignment analysis inferred the key residues K267, H162, N86, E189, and T244 for AlgVR7 catalysis, and it is derived from the PL7 family; exhibited high activity towards sodium alginate, polyM (PM), and polyG (PG); and can also degrade polygalacturonic acid (PGA) efficiently, with the highest affinity and catalytic efficiency for the MG block of the substrate. The optimal temperature and pH for AlgVR7 were determined to be 40 °C and pH 8, respectively. The enzyme activity of AlgVR7 was maximum at 40 °C, 40% of the enzyme activity was retained after incubation at 60 °C for 60 min, and enzyme activity was still present after 60 min incubation. AlgVR7 activity was stimulated by 100 Mm NaCl, indicating a halophilic nature and suitability for marine environments. Degradation products analyzed using ESI-MS revealed that the enzyme primarily produced trisaccharides and tetrasaccharides. At 40 °C and pH 8.0, its Km values for sodium alginate, PM, and PG were 16.67 μmol, 13.12 μmol, and 22.86 μmol, respectively. Structural analysis and molecular docking studies unveiled the key catalytic residues involved in substrate recognition and interaction. Glu167 was identified as a critical residue for the PL7_5 subfamily, uniquely playing an essential role in alginate decomposition. Overall, AlgVR7 exhibits great potential as a powerful bifunctional enzyme for the efficient preparation of alginate oligosaccharides, with promising applications in biotechnology and industrial fields.

Alginate oligosaccharides (AOS), products of alginate degradation by endotype alginate lyases, possess favorable biological activities and have broad applications. Although many have been reported, alginate lyases with homogeneous AOS products and secretory production by an engineered host are scarce. Herein, the alginate lyase AlyC7 from Vibrio sp. C42 was characterized as a trisaccharide-producing lyase exhibiting high activity and broad substrate specificity. With PelB as the signal peptide and 500 mM glycine as the additive, the extracellular production of AlyC7 in Escherichia coli reached 1122.8 U/mL after 27 h cultivation in Luria-Bertani medium. The yield of trisaccharides from sodium alginate degradation by the produced AlyC7 reached 758.6 mg/g, with a purity of 85.1%. The prepared AOS at 20 μg/mL increased the root length of lettuce, tomato, wheat, and maize by 27.5%, 25.7%, 9.7%, and 11.1%, respectively. This study establishes a robust foundation for the industrial and agricultural applications of AlyC7.

Alginate is a natural polysaccharide present in various marine brown seaweeds. Alginate oligosaccharide (AOS) is a degradation product of alginate, which has received increasing attention due to its low molecular weight and promising biological activity. The wide-ranging biological activity of AOS is closely related to the diversity of their structures. AOS with a specific structure and distinct applications can be obtained by different methods of alginate degradation. This review focuses on recent advances in the biological activity of alginate and its derivatives, including their anti-tumor, anti-oxidative, immunoregulatory, anti-inflammatory, neuroprotective, antibacterial, hypolipidemic, antihypertensive, and hypoglycemic properties, as well as the ability to suppress obesity and promote cell proliferation and regulate plant growth. We hope that this review will provide theoretical basis and inspiration for the high-value research developments and utilization of AOS-related products.

Alginate lyases depolymerize alginate and generate alginate oligosaccharides (AOS) and eventually 4‐deoxy‐L‐erythro‐5‐hexoseulose uronate (DEH), a monosaccharide. Recently, alginate lyases have garnered significant attention due to the increasing demand for AOS, which exhibit bioactivities beneficial to human health, livestock productivity, and agricultural efficiency. Additionally, these enzymes play a crucial role in producing DEH, essential in alginate catabolism in bacteria. This review explains the industrial value of AOS and DEH, which contribute broadly to industries ranging from the food industry to biorefinery processes. This review also highlights recent advances in alginate lyase applications and engineering, including domain truncation, chimeric enzyme design, rational mutagenesis, and directed evolution. These approaches have enhanced enzyme performance for efficient AOS and DEH production. We also discuss current challenges and future directions toward industrial‐scale bioconversion of alginate‐rich biomass. This review covers alginate lyases that depolymerise alginate into AOS (alginate oligosaccharides) and DEH (4‐deoxy‐L‐erythro‐5‐hexoseulose uronate). It discusses the industrial applications of AOS and DEH in food, agriculture, and biorefinery processes. Additionally, it explores recent advancements in enzyme engineering, including chimeric enzyme construction, truncation, computer‐aided design, and directed evolution, to enhance alginate lyase efficiency.

Alginate, the most abundant polysaccharides of brown algae, consists of various proportions of uronic acid epimers α-L-guluronic acid (G) and β-D-mannuronic acid (M). Alginate oligosaccharides (AOs), the degradation products of alginates, exhibit excellent bioactivities and a great potential for broad applications in pharmaceutical fields. Alginate lyases can degrade alginate to functional AOs with unsaturated bonds or monosaccharides, which can facilitate the biorefinery of brown algae. On account of the increasing applications of AOs and biorefinery of brown algae, there is a scientific need to explore the important aspects of alginate lyase, such as catalytic mechanism, structure, and property. This review covers fundamental aspects and recent developments in basic information, structural characteristics, the structure–substrate specificity or catalytic efficiency relationship, property, molecular modification, and applications. To meet the needs of biorefinery systems of a broad array of biochemical products, alginate lyases with special properties, such as salt-activated, wide pH adaptation range, and cold adaptation are outlined. Withal, various challenges in alginate lyase research are traced out, and future directions, specifically on the molecular biology part of alginate lyases, are delineated to further widen the horizon of these exceptional alginate lyases.

The main challenge in extrusion‐based bioprinting is to develop inks which must comprise a manifold of characteristics before, during, and after printing. To tackle the challenge of good shape fidelity and printability of low concentration inks, in this study hydrogel microparticles (HMPs) are proposed to produce internally pre‐crosslinked inks. Alginate (Alg) and oxidized alginate (OA)‐based HMPs are fabricated and used as Ca2+‐releasing reservoirs. OA HMPs are used to demonstrate the versatility of this approach and to show its suitability also for chemically modified alginate. Embedded in either fresh Alg or OA solution, HMPs are used to pre‐crosslink the inks. Rheological measurements revealed that HMP pre‐crosslinking increases the yield stress and viscosity while reducing the loss angle of bioinks. Moreover, printing experiments reveal that being able to tailor rheological properties is an effective tool to improve printability. Furthermore, pre‐crosslinking significantly alters the hydogel internal microstructure. In vitro studies show that NIH/3T3 cells proliferate in HMP pre‐crosslinked bioinks modified with gelatin. Altogether, a low‐cost and easy to use setup to prepare HMPs is presented and for the first time, the possibility of using such HMPs as pre‐crosslinking agent to tailor the printability of alginate‐based bioinks is demonstrated. Hydrogel microparticles (HMPs) are used to produce internally pre‐crosslinked alginate‐based bioinks for 3D bioprinting. Alginate and oxidized alginate‐based HMPs are fabricated and used as Ca2+‐releasing reservoirs. Printing experiments reveal improved printability. The approach is based on low‐cost, easy to prepare HMPs demonstrating the possibility of using HMPs as pre‐crosslinking agent to tailor the printability of alginate‐based bioinks.