A review about brown algal cell walls and fucose-containing sulfated polysaccharides: Cell wall context, biomedical properties and key research challenges

Cell wall structural changes lead to separation and shedding of biofouled epidermal cell wall layers by the brown alga Ascophyllum nodosum

Marine plants control the accumulation of biofouling organisms (epibionts) on their surfaces by various chemical and physical means. Ascophyllum nodosum is a perennial multicellular brown alga known to shed patches of epidermal material, thus removing epibionts and exposing unfouled surfaces to another cycle of colonization. While surface shedding is documented in multiple marine macroalgae, the cell and developmental biology of the phenomenon is almost unexplored. A previous investigation of Ascophyllum not only revealed regular cycles of epibiont accumulation and epidermal shedding but also stimulated the development of methods to detect the corresponding changes in epidermal (meristoderm) cells that are reported here. Confocal laser scanning microscopy of cell walls and cytoplasm fluorescently stained with Solophenyl Flavine 7GFE (Direct Yellow 96) and the lipophilic dye Rhodamine B (respectively) was combined with light and electron microscopy of chemically fixed or freeze-substituted tissues. As epibionts accumulated, epidermal cells generated thick, apical cell walls in which differentially stained central layers subsequently developed, marking the site of future cell wall separation. During cell wall separation, the outermost part of the cell wall and its epibionts plus the upper parts of the anticlinal walls between neighboring cells detached in a layer from multiple epidermal cells, exposing the remaining inner part of the cell wall to new colonizing organisms. These findings highlight the dynamic nature of apical cell wall structure and composition in response to colonizing organisms and lay a foundation for further investigations on the periodic removal of biofouling epibionts from the surface of Ascophyllum fronds.

Current Research Landscape of Marine-Derived Anti-Atherosclerotic Substances

Atherosclerosis is a chronic disease characterized by lipid accumulation and chronic inflammation of the arterial wall, which is the pathological basis for coronary heart disease, cerebrovascular disease and thromboembolic disease. Currently, there is a lack of low-cost therapeutic agents that effectively slow the progression of atherosclerosis. Therefore, the development of new drugs is urgently needed. The research and development of marine-derived drugs have gained increasing interest from researchers across the world. Many marine organisms provide a rich material basis for the development of atherosclerotic drugs. This review focuses on the latest technological advances in the structures and mechanisms of action of marine-derived anti-atherosclerotic substances and the challenges of the application of these substances including marine polysaccharides, proteins and peptides, polyunsaturated fatty acids and small molecule compounds. Here, we describe the theoretical basis of marine biological resources in the treatment of atherosclerosis.

Sulfated Polysaccharides from Marine Algae as a Basis of Modern Biotechnologies for Creating Wound Dressings: Current Achievements and Future Prospects

Wound healing involves a complex cascade of cellular, molecular, and biochemical responses and signaling processes. It consists of successive interrelated phases, the duration of which depends on a multitude of factors. Wound treatment is a major healthcare issue that can be resolved by the development of effective and affordable wound dressings based on natural materials and biologically active substances. The proper use of modern wound dressings can significantly accelerate wound healing with minimum scar mark. Sulfated polysaccharides from seaweeds, with their unique structures and biological properties, as well as with a high potential to be used in various wound treatment methods, now undoubtedly play a major role in innovative biotechnologies of modern natural interactive dressings. These natural biopolymers are a novel and promising biologically active source for designing wound dressings based on alginates, fucoidans, carrageenans, and ulvans, which serve as active and effective therapeutic tools. The goal of this review is to summarize available information about the modern wound dressing technologies based on seaweed-derived polysaccharides, including those successfully implemented in commercial products, with a focus on promising and innovative designs. Future perspectives for the use of marine-derived biopolymers necessitate summarizing and analyzing results of numerous experiments and clinical trial data, developing a scientifically substantiated approach to wound treatment, and suggesting relevant practical recommendations.

Verrucomicrobia use hundreds of enzymes to digest the algal polysaccharide fucoidan

Brown algae are important players in the global carbon cycle by fixing carbon dioxide into 1 Gt of biomass annually, yet the fate of fucoidan-their major cell wall polysaccharide-remains poorly understood. Microbial degradation of fucoidans is slower than that of other polysaccharides, suggesting that fucoidans are more recalcitrant and may sequester carbon in the ocean. This may be due to the complex, branched and highly sulfated structure of fucoidans, which also varies among species of brown algae. Here, we show that 'Lentimonas' sp. CC4, belonging to the Verrucomicrobia, acquired a remarkably complex machinery for the degradation of six different fucoidans. The strain accumulated 284 putative fucoidanases, including glycoside hydrolases, sulfatases and carbohydrate esterases, which are primarily located on a 0.89-megabase pair plasmid. Proteomics reveals that these enzymes assemble into substrate-specific pathways requiring about 100 enzymes per fucoidan from different species of brown algae. These enzymes depolymerize fucoidan into fucose, which is metabolized in a proteome-costly bacterial microcompartment that spatially constrains the metabolism of the toxic intermediate lactaldehyde. Marine metagenomes and microbial genomes show that Verrucomicrobia including 'Lentimonas' are abundant and highly specialized degraders of fucoidans and other complex polysaccharides. Overall, the complexity of the pathways underscores why fucoidans are probably recalcitrant and more slowly degraded, since only highly specialized organisms can effectively degrade them in the ocean.

Inhibition of glucuronomannan hexamer on the proliferation of lung cancer through binding with immunoglobulin G

The anti-lung cancer activity of oligosaccharides derived from glucuronomannan was investigated. The inhibition of A549 cell proliferation by glucuronomannan (Gn) and its oligomers (dimer (G2), tetramer (G4) and hexamer (G6)) were concentration dependent. In vivo activities on the A549-derived tumor xenografts showed the tumor inhibition of G2, G4 and G6 were 17 %, 40 % and 46 %, respectively. Organ coefficients in nude mice showed an increase in the kidney with G4, the brain with G6, and the spleen with G6. An advanced tandem mass tag labeled proteomics approach was performed. A significant differential expression was found in 59 out of the 4371 proteins, which involved the immune system. Surface plasmon resonance (SPR) studies revealed G6 was strongly bound to immunoglobulin G. This suggests that glucuronomannan hexamer inhibits the proliferation of lung cancer through its binding to immunoglobulin.

Enzyme-Assisted Fucoidan Extraction from Brown Macroalgae Fucus distichus subsp. evanescens and Saccharina latissima

Fucoidans from brown macroalgae (brown seaweeds) have different structures and many interesting bioactivities. Fucoidans are classically extracted from brown seaweeds by hot acidic extraction. Here, we report a new targeted enzyme-assisted methodology for fucoidan extraction from brown seaweeds. This enzyme-assisted extraction protocol involves a one-step combined use of a commercial cellulase preparation (Cellic®CTec2) and an alginate lyase from Sphingomonas sp. (SALy), reaction at pH 6.0, 40 °C, removal of non-fucoidan polysaccharides by Ca2+ precipitation, and ethanol-precipitation of crude fucoidan. The workability of this method is demonstrated for fucoidan extraction from Fucus distichus subsp. evanescens (basionym Fucus evanescens) and Saccharina latissima as compared with mild acidic extraction. The crude fucoidans resulting directly from the enzyme-assisted method contained considerable amounts of low molecular weight alginate, but this residual alginate was effectively removed by an additional ion-exchange chromatographic step to yield pure fucoidans (as confirmed by 1H NMR). The fucoidan yields that were obtained by the enzymatic method were comparable to the chemically extracted yields for both F. evanescens and S. latissima, but the molecular sizes of the fucoidans were significantly larger with enzyme-assisted extraction. The molecular weight distribution of the fucoidan fractions was 400 to 800 kDa for F. evanescens and 300 to 800 kDa for S. latissima, whereas the molecular weights of the corresponding chemically extracted fucoidans from these seaweeds were 10-100 kDa and 50-100 kDa, respectively. Enzyme-assisted extraction represents a new gentle strategy for fucoidan extraction and it provides new opportunities for obtaining high yields of native fucoidan structures from brown macroalgae.

Fucoidans: Downstream Processes and Recent Applications

Fucoidans are multifunctional marine macromolecules that are subjected to numerous and various downstream processes during their production. These processes were considered the most important abiotic factors affecting fucoidan chemical skeletons, quality, physicochemical properties, biological properties and industrial applications. Since a universal protocol for fucoidans production has not been established yet, all the currently used processes were presented and justified. The current article complements our previous articles in the fucoidans field, provides an updated overview regarding the different downstream processes, including pre-treatment, extraction, purification and enzymatic modification processes, and shows the recent non-traditional applications of fucoidans in relation to their characters.

Extraction and Modification of Macroalgal Polysaccharides for Current and Next-Generation Applications

Marine macroalgal (seaweed) polysaccharides are highly promising for next-generation applications in several industries. However, despite the reported comprehensive potential of these polysaccharides, commercial products are scarce on the market. Seaweed cultivations are increasing in number and production quantity, owing to an elevated global trend of utilization interest in seaweed. The extraction of polysaccharides from seaweed generally generates low yields, but novel methods are being developed to facilitate and improve the extraction processes. Current areas of applications for seaweed polysaccharides mainly take advantage of the physicochemical properties of certain polysaccharides, such as gelling, thickening and emulsifying. However, many of the numerous bioactivities reported are still only at research level and lack clinical evidence for commercialization. It has been suggested the construction of smaller units may generate better defined molecules that are more suitable for biomedical applications. Enzymatic modification is a promising tool for the generation of more defined, targeted biomolecules. This review covers; structural differences between the most predominant marine algal polysaccharides, extraction processes, modification alternatives, as well as a summary of current and potential next-generation application areas.

Degradation of different molecular weight fucoidans and their inhibition of TGF-β1 induced epithelial-mesenchymal transition in mouse renal tubular epithelial cells

In order to investigate the anti-fibrotic effect of different molecular weight (Mw) fucoidans on TGF-β1-induced mouse renal tubular epithelial cell (MTEC) mode. Oxidative degradation method was used to obtain fucoidans with different molecular weights and the reaction time, reaction temperature and the concentration of oxidants were investigated. Cell viability was detected by CCK-8, and EMT markers expression was detected by Western-bolt and Cell immunofluorescence assay. As a result, after chemical analysis of three independent batches of prepared samples, one batch of fucoidan sample (LHX 1-9) which chemical contents are similar but Mw ranging from 3.3 KDa to 49.3 KDa were selected to do further research. We found LHX1 (Mw = 3.3 KDa) and LHX 3-9 (Mw = 6.6 KDa, 8.3 KDa, 11.3 KDa, 14.9 KDa, 25.2 KDa, 35.4 KDa, 49.3 KDa) could resist the TGF-β1-induced depithelial-mesenchymal transition (EMT) by decreased expression of Fn and CTGF and maintained epithelial cell morphology in MTEC. However, the relationship between the Mw of fucoidans and their anti-EMT effect is not simply linear. Among the samples, LHX 1, 5 and 8 showed significant anti-EMT effects than others by de-regulated Fn and CTGF expression on MTEC cells.

A comparative study of sulphated polysaccharide effects on advanced glycation end-product uptake and scavenger receptor class A level in macrophages

Advanced glycation end-products, especially toxic advanced glycation end-products derived from glyceraldehyde (advanced glycation end-product-2) and glycolaldehyde (advanced glycation end-product-3), are biologically reactive compounds associated with diabetic complications. We previously demonstrated that toxic advanced glycation end-products were internalised into macrophage-like RAW264.7 cells through scavenger receptor-1 class A (CD204). Toxic advanced glycation end-product uptake was inhibited by fucoidan, a sulphated polysaccharide and antagonistic ligand for scavenger receptors, suggesting that sulphated polysaccharides are emerging candidates for treatment of advanced glycation end-product-related diseases. In this study, we compared the effects of six types of sulphated and non-sulphated polysaccharides on toxic advanced glycation end-product uptake in RAW264.7 cells. Fucoidan, carrageenan and dextran sulphate attenuated toxic advanced glycation end-product uptake. Fucoidan and carrageenan inhibited advanced glycation end-product-2-induced upregulation of SR-A, while advanced glycation end-product-3-induced upregulation of scavenger receptor-1 class A was only suppressed by fucoidan. Dextran sulphate did not affect scavenger receptor-1 class A levels in toxic advanced glycation end-product-treated cells. Chondroitin sulphate, heparin and hyaluronic acid failed to attenuate toxic advanced glycation end-product uptake. Heparin and hyaluronic acid had no effect on scavenger receptor-1 class A levels, while chondroitin sulphate inhibited advanced glycation end-product-3-induced upregulation of scavenger receptor-1 class A. Taken together, fucoidan and carrageenan, but not the other sulphated polysaccharides examined, had inhibitory activities on toxic advanced glycation end-product uptake and toxic advanced glycation end-product-induced upregulation of scavenger receptor-1 class A, possibly because of structural differences among sulphated polysaccharides.

Presence of Exogenous Sulfate Is Mandatory for Tip Growth in the Brown Alga Ectocarpus subulatus

Brown algae (Phaeophyceae) are multicellular photoautrophic organisms and the largest biomass producers in coastal regions. A variety of observations indicate that their extracellular matrix (ECM) is involved with screening of salts, development, cell fate selection, and defense responses. It is likely that these functionalities are related to its constitutive structures. The major components of the ECM of brown algae are β-glucans, alginates, and fucose-containing sulfated polysaccharides. The genus Ectocarpus comprises a wide range of species that have adapted to different environments, including isolates of Ectocarpus subulatus, a species highly resistant to low salinity. Previous studies on a freshwater strain of E. subulatus indicated that the sulfate remodeling of fucans is related to the external salt concentration. Here we show that the sulfate content of the surrounding medium is a key parameter influencing both the patterning of the alga and the occurrence of the BAM4 sulfated fucan epitope in walls of apical cells. These results indicate that sulfate uptake and incorporation in the sulfated fucans from apical cells is an essential parameter to sustain tip growth, and we discuss its influence on the architectural plasticity of Ectocarpus.

Diversity of Sulfated Polysaccharides From Cell Walls of Coenocytic Green Algae and Their Structural Relationships in View of Green Algal Evolution

Seaweeds biosynthesize sulfated polysaccharides as key components of their cell walls. These polysaccharides are potentially interesting as biologically active compounds. Green macroalgae of the class Ulvophyceae comprise sulfated polysaccharides with great structural differences regarding the monosaccharide constituents, linearity of their backbones, and presence of other acidic substituents in their structure, including uronic acid residues and pyruvic acid. These structures have been thoroughly studied in the Ulvales and Ulotrichales, but only more recently have they been investigated with some detail in ulvophytes with giant multinucleate (coenocytic) cells, including the siphonous Bryopsidales and Dasycladales, and the siphonocladous Cladophorales. An early classification of these structurally heterogeneous polysaccharides was based on the presence of uronic acid residues in these molecules. In agreement with this classification based on chemical structures, sulfated polysaccharides of the orders Bryopsidales and Cladophorales fall in the same group, in which this acidic component is absent, or only present in very low quantities. The cell walls of Dasycladales have been less studied, and it remains unclear if they comprise sulfated polysaccharides of both types. Although in the Bryopsidales and Cladophorales the most important sulfated polysaccharides are arabinans and galactans (or arabinogalactans), their major structures are very different. The Bryopsidales produce sulfated pyruvylated 3-linked β-d-galactans, in most cases, with ramifications on C6. For some species, linear sulfated pyranosic β-l-arabinans have been described. In the Cladophorales, also sulfated pyranosic β-l-arabinans have been found, but 4-linked and highly substituted with side chains. These differences are consistent with recent molecular phylogenetic analyses, which indicate that the Bryopsidales and Cladophorales are distantly related. In addition, some of the Bryopsidales also biosynthesize other sulfated polysaccharides, i.e., sulfated mannans and sulfated rhamnans. The presence of sulfate groups as a distinctive characteristic of these biopolymers has been related to their adaptation to the marine environment. However, it has been shown that some freshwater algae from the Cladophorales also produce sulfated polysaccharides. In this review, structures of sulfated polysaccharides from bryopsidalean, dasycladalean, and cladophoralean green algae studied until now are described and analyzed based on current phylogenetic understanding, with the aim of unveiling the important knowledge gaps that still exist.

The Potential of Fucose-Containing Sulfated Polysaccharides As Scaffolds for Biomedical Applications

Marine environments have a high quantity and diversity of sulfated polysaccharides. In coastal regions brown algae are the most abundant biomass producers and their cell walls have fucosecontaining sulfated polysaccharides (FCSP), known as fucans and/or fucoidans. These sulfated compounds have been widely researched for their biomedical properties, namely the immunomodulatory, haemostasis, pathogen inhibition, anti-inflammatory capacity, and antitumoral. These activities are probably due to their ability to mimic the carbohydrate moieties of mammalian glycosaminoglycans. Therefore, the FCSP are interesting compounds for application in health-related subjects, mainly for developing scaffolds for delivery systems or tissue regeneration. FCSP showed potential for these applications also due to their ability to form stable 3D structures with other polymers able to entrap therapeutic agents or cell and growth factors, besides their biocompatibility and biodegradability. However, for the clinical use of these biopolymers well-defined reproducible molecules are required in order to accurately establish relationships between structural features and human health applications.

Macroalgae Derived Fungi Have High Abilities to Degrade Algal Polymers

Marine fungi associated with macroalgae are an ecologically important group that have a strong potential for industrial applications. In this study, twenty-two marine fungi isolated from the brown seaweed Fucus sp. were examined for their abilities to produce algal and plant biomass degrading enzymes. Growth of these isolates on brown and green algal biomass revealed a good growth, but no preference for any specific algae. Based on the analysis of enzymatic activities, macroalgae derived fungi were able to produce algae specific and (hemi-)cellulose degrading enzymes both on algal and plant biomass. However, the production of algae specific activities was lower than the production of cellulases and xylanases. These data revealed the presence of different enzymatic approaches for the degradation of algal biomass by macroalgae derived fungi. In addition, the results of the present study indicate our poor understanding of the enzymes involved in algal biomass degradation and the mechanisms of algal carbon source utilization by marine derived fungi.

The macromolecular composition of noncalcified marine macroalgae

The macromolecular composition of macroalgae influences nutrient flow and food quality in aquatic ecosystems and the value of macroalgae species for human consumption, aquaculture, biofuels, and other applications. We used literature data (125 publications, 1,117 observations) and a hierarchal Bayesian statistical model to estimate the average macromolecular composition, protein, lipid, and carbohydrate of macroalgae as a whole and at the phylum level. Our focus was on marine, noncalcified macroalgae sampled from wild-grown populations in the field. We found that the median macromolecular composition is 9.98% protein, 2.7% lipid, 48.5% carbohydrate, and 31.8% ash as percent dry weight. We compared the median macromolecular content of macroalgae to microalgae and herbaceous plants and test for differences in macromolecular content across macroalgal phyla. Macroalgae were much more enriched in carbohydrate and minerals than the microalgae and lower in protein and lipid than many herbaceous plants. Rhodophyte macroalgae have significantly less lipid and more protein and the Ochrophyte macroalgae have significantly less protein than the average.

Polysaccharides of mushroom Pleurotus spp.: New extraction techniques, biological activities and development of new technologies

The biodiversity of mushrooms Pleurotus spp. is impressive due to its complexity and diversity related to the composition of chemical structures such as polysaccharides, glycoproteins and secondary metabolites such as alkaloids, flavonoids and betalains. Recent studies of polysaccharides and their structural elucidation have helped to direct research and development of technologies related to pharmacological action, production of bioactive foods and application of new, more sophisticated extraction tools. The diversity of bioactivities related to these biopolymers, their mechanisms and routes of action are constant focus of researches. The elucidation of bioactivities has helped to formulate new vaccines and targeted drugs. In this context, in terms of polysaccharides and the diversity of mushrooms Pleurotus spp., this review seeks to revisit the genus, making an updated approach on the recent discoveries of polysaccharides, new extraction techniques and bioactivities, emphasising on their mechanisms and routes in order to update the reader on the recent technologies related to these polymers.

Indole‑6‑carboxaldehyde isolated from Sargassum thunbergii inhibits the expression and secretion of matrix metalloproteinase‑9

Sargassum thunbergii is a brown alga from which various bioactive compounds can be extracted. Among these, the activities of indole derivatives, particularly as potential inhibitors of matrix metalloproteinases (MMPs), and their underlying mechanisms have been rarely investigated. Therefore, we evaluated the inhibitory effects of indole‑6‑carboxaldehyde (I6CA) on MMP‑9 by gelatin zymography and western blot anlaysis. We used phorbol 12‑myristate 13‑acetate (PMA), which is known to induce MMP‑9 expression and secretion, to stimulate HT1080 cells. Our results revealed that I6CA significantly inhibited MMP‑9 expression and secretion, without significantly affecting the viability of PMA‑stimulated HT1080 cells. Our mechanistic studies indicated that I6CA suppressed the phosphorylation and activation of two mitogen‑activated protein kinases (MAPKs), c‑Jun N‑terminal kinase (JNK) and extracellular signal‑regulated kinase 1/2 (ERK). Furthermore, I6CA inhibited the phosphorylation of inhibitor of κBα (IκBα) in response to PMA stimulation, which suppressed nuclear factor‑κB (NF‑κB) p65 subunit nuclear translocation. Collectively, I6CA was determined to suppress MMP‑9 expression and secretion, and effects were proposed to be mediated via the inhibition of the MAPK and NF‑κB p65 pathways. Therefore, we suggested I6CA to be a potential therapeutic agent for MMP‑9‑related processes, including tumor invasion and metastasis; however, further investigation is required.

Sargassum Seaweed as a Source of Anti-Inflammatory Substances and the Potential Insight of the Tropical Species: A Review

Sargassum is recognized both empirically and scientifically as a potential anti-inflammatory agent. Inflammation is an important response in the body that helps to overcome various challenges to body homeostasis such as microbial infections, tissue stress, and certain injuries. Excessive and uncontrolled inflammatory conditions can affect the pathogenesis of various diseases. This review aims to explore the potential of Sargassum's anti-inflammatory activity, not only in crude extracts but also in sulfated polysaccharides and purified compounds. The tropical region has a promising availability of Sargassum biomass because its climate allows for the optimal growth of seaweed throughout the year. This is important for its commercial utilization as functional ingredients for both food and non-food applications. To the best of our knowledge, studies related to Sargassum's anti-inflammatory activity are still dominated by subtropical species. Studies on tropical Sargassum are mainly focused on the polysaccharides group, though there are some other potentially bioactive compounds such as polyphenols, terpenoids, fucoxanthin, fatty acids and their derivatives, typical polar lipids, and other groups. Information on the modulation mechanism of Sargassum's bioactive compounds on the inflammatory response is also discussed here, but specific mechanisms related to the interaction between bioactive compounds and targets in cells still need to be further studied.

Effects of Sulfated Fucans from Laminaria hyperborea Regarding VEGF Secretion, Cell Viability, and Oxidative Stress and Correlation with Molecular Weight

BACKGROUND

Sulfated fucans show interesting effects in the treatment of ocular diseases (e.g., age-related macular degeneration), depending on their chemical structure. Here, we compared three purified sulfated fucans from Laminaria hyperborea (LH) regarding cell viability, oxidative stress protection, and vascular endothelial growth factor (VEGF) secretion in ocular cells.

METHODS

High-molecular-weight sulfated fucan (Mw = 1548.6 kDa, Fuc1) was extracted with warm water and purified through ultrafiltration. Lower-molecular-weight samples (Mw = 499 kDa, Fuc2; 26.9 kDa, Fuc3) were obtained by mild acid hydrolysis of ultrapurified sulfated fucan and analyzed (SEC-MALS (Size-exclusion chromatography-Multi-Angle Light Scattering), ICP-MS, and GC). Concentrations between 1 and 100 µg/mL were tested. Cell viability was measured after 24 h (uveal melanoma cell line (OMM-1), retinal pigment epithelium (RPE) cell line ARPE-19, primary RPE cells) via MTT/MTS (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide/3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Oxidative stress protection was determined after 24 h (OMM-1, ARPE-19). VEGF secretion was analyzed via ELISA after three days (ARPE-19, RPE).

RESULTS

Fuc2 and Fuc3 were antiproliferative for OMM-1, but not for ARPE. Fuc1 protected OMM-1. VEGF secretion was lowered with all fucans except Fuc3 in ARPE-19 and RPE. The results suggest a correlation between molecular weight and biological activity, with efficiency increasing with size.

CONCLUSION

The LH sulfated fucan Fuc1 showed promising results regarding VEGF inhibition and protection, encouraging further medical research.

Discovery of a novel quinohemoprotein from a eukaryote and its application in electrochemical devices

Pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase is one of the extensively studied sugar-oxidizing enzymes used as a biocatalyst for biosensors and biofuel cells. A novel pyranose dehydrogenase (CcPDH) derived from the basidiomycete Coprinopsis cinerea is the first discovered eukaryotic PQQ-dependent enzyme. This enzyme carries a b-type cytochrome domain that is homologous to the cytochrome domain of cellobiose dehydrogenase (CDH); thus, CcPDH is a quinohemoprotein. CcPDH catalyzes the oxidation of various aldose sugars and shows significant activity toward the reverse-chair conformation of pyranoses. Interdomain electron transfer occurs in CcPDH similar to CDH, from the PQQ cofactor in the catalytic domain to the heme b in the cytochrome domain. This enzyme is able to direct electrical communication with electrodes, without artificial electron mediators, thus allowing direct electron transfer (DET)-type bioelectrocatalysis. In this review, we briefly describe recent progress in research on the biochemical discovery of CcPDH and the development of (bio)electrochemical applications (an amperometric biosensor) based on DET reactions.

Alginates along the filament of the brown alga Ectocarpus help cells cope with stress

Ectocarpus is a filamentous brown alga, which cell wall is composed mainly of alginates and fucans (80%), two non-crystalline polysaccharide classes. Alginates are linear chains of epimers of 1,4-linked uronic acids, β-D-mannuronic acid (M) and α-L-guluronic acid (G). Previous physico-chemical studies showed that G-rich alginate gels are stiffer than M-rich alginate gels when prepared in vitro with calcium. In order to assess the possible role of alginates in Ectocarpus, we first immunolocalised M-rich or G-rich alginates using specific monoclonal antibodies along the filament. As a second step, we calculated the tensile stress experienced by the cell wall along the filament, and varied it with hypertonic or hypotonic solutions. As a third step, we measured the stiffness of the cell along the filament, using cell deformation measurements and atomic force microscopy. Overlapping of the three sets of data allowed to show that alginates co-localise with the stiffest and most stressed areas of the filament, namely the dome of the apical cell and the shanks of the central round cells. In addition, no major distinction between M-rich and G-rich alginate spatial patterns could be observed. Altogether, these results support that both M-rich and G-rich alginates play similar roles in stiffening the cell wall where the tensile stress is high and exposes cells to bursting, and that these roles are independent from cell growth and differentiation.

Proteomic enzyme analysis of the marine fungus Paradendryphiella salina reveals alginate lyase as a minimal adaptation strategy for brown algae degradation

We set out to investigate the genetic adaptations of the marine fungus Paradendryphiella salina CBS112865 for degradation of brown macroalgae. We performed whole genome and transcriptome sequencing and shotgun proteomic analysis of the secretome of P. salina grown on three species of brown algae and under carbon limitation. Genome comparison with closely related terrestrial fungi revealed that P. salina had a similar but reduced CAZyme profile relative to the terrestrial fungi except for the presence of three putative alginate lyases from Polysaccharide Lyase (PL) family 7 and a putative PL8 with similarity to ascomycete chondroitin AC lyases. Phylogenetic and homology analyses place the PL7 sequences amongst mannuronic acid specific PL7 proteins from marine bacteria. Recombinant expression, purification and characterization of one of the PL7 genes confirmed the specificity. Proteomic analysis of the P. salina secretome when growing on brown algae, revealed the PL7 and PL8 enzymes abundantly secreted together with enzymes necessary for degradation of laminarin, cellulose, lipids and peptides. Our findings indicate that the basic CAZyme repertoire of saprobic and plant pathogenic ascomycetes, with the addition of PL7 alginate lyases, provide P. salina with sufficient enzymatic capabilities to degrade several types of brown algae polysaccharides.

Identification, classification, and evolution of putative xylosyltransferases from algae

Xylosyltransferases (XylTs) play key roles in the biosynthesis of many different polysaccharides. These enzymes transfer D-xylose from UDP-xylose to substrate acceptors. In this study, we identified 30 XylTs from primary endosymbionts (green algae, red algae, and glaucophytes) and secondary or higher endosymbionts (brown algae, diatoms, Eustigmatophyceae, Pelagophyceae, and Cryptophyta). We performed comparative phylogenetic studies on key XylT subfamilies, and investigated the functional divergence of genes using RNA-Seq. Of the 30 XylTs, one β-1,4-XylT IRX14-related, one β-1,4 XylT IRX10L-related, and one xyloglucan 6-XylT 1-related gene were identified in the Charophyta, showing strong similarities to their land plant descendants. This implied the ancient occurrence of xylan and xyloglucan biosynthetic machineries in Charophyta. The other 27 XylTs were identified as UDP-D-xylose: L-fucose-α-1,3-D-XylT (FucXylT) type that specifically transferred D-xylose to fucose. We propose that FucXylTs originated from the last eukaryotic common ancestor, rather than being plant specific, because they are also distributed in Choanoflagellatea and Echinodermata. Considering the evidence from many aspects, we hypothesize that the FucXylTs likely participated in fucoidan biosynthesis in brown algae. We provide the first insights into the evolutionary history and functional divergence of FucXylT in algal biology.

Subcritical water extraction as an efficient technique to isolate biologically-active fucoidans from Nizamuddinia zanardinii

A sulfated polysaccharide (fucoidan) has been isolated from Nizamuddinia zanardinii using subcritical water extraction method (SCWE), and extraction conditions were optimised using the response surface methodology. The optimum extraction conditions were found to be: extraction time of 29 min, extraction temperature of 150 °C, and raw material-to-water ratio of 21 g/mL. The fucoidan yield under these optimum conditions was 25.98%, which was considerably higher than that of conventional solvent extraction (5.2%). Extraction time and temperature were the extraction variables that most significantly affected fucoidan yield. Chemical and monosaccharide composition, molecular weight, and the antioxidant, anticancer and immunomodulatory activities of the extract have also been investigated. The monosaccharide composition of fucoidan included fucose (34.13%), mannose (30.70%), galactose (23.19%), xylose (9.35%) and glucose (2.65%). The average molecular weight of the extracted fucoidan was 694 kDa. Antioxidant results revealed that SCWE-extracted fucoidan had appreciable ABTS radical scavenging (70.35%) and reducing power (0.182 Abs). The anticancer activity of fucoidan ranged from 24.60 to 49.46% for HeLa cells and from 23.95 to 46.78% for HepG2 cells. The NO production of RAW264.7 cells was observed to be dose-dependent, while maximum NO production was found to be 34.82 μmol at a 50 μg/mL fucoidan concentration.

Xylans of Red and Green Algae: What Is Known about Their Structures and How They Are Synthesised?

Xylans with a variety of structures have been characterised in green algae, including chlorophytes (Chlorophyta) and charophytes (in the Streptophyta), and red algae (Rhodophyta). Substituted 1,4-β-d-xylans, similar to those in land plants (embryophytes), occur in the cell wall matrix of advanced orders of charophyte green algae. Small proportions of 1,4-β-d-xylans have also been found in the cell walls of some chlorophyte green algae and red algae but have not been well characterised. 1,3-β-d-Xylans occur as triple helices in microfibrils in the cell walls of chlorophyte algae in the order Bryopsidales and of red algae in the order Bangiales. 1,3;1,4-β-d-Xylans occur in the cell wall matrix of red algae in the orders Palmariales and Nemaliales. In the angiosperm Arabidopsis thaliana, the gene IRX10 encodes a xylan 1,4-β-d-xylosyltranferase (xylan synthase), and, when heterologously expressed, this protein catalysed the production of the backbone of 1,4-β-d-xylans. An orthologous gene from the charophyte green alga Klebsormidium flaccidum, when heterologously expressed, produced a similar protein that was also able to catalyse the production of the backbone of 1,4-β-d-xylans. Indeed, it is considered that land plant xylans evolved from xylans in ancestral charophyte green algae. However, nothing is known about the biosynthesis of the different xylans found in chlorophyte green algae and red algae. There is, thus, an urgent need to identify the genes and enzymes involved.

Biomolecular Composition and Revenue Explained by Interactions between Extrinsic Factors and Endogenous Rhythms of Saccharina latissima

This review provides a systematic overview of the spatial and temporal variations in the content of biomolecular constituents of Saccharina latissima on the basis of 34 currently-available scientific studies containing primary measurements. We demonstrate the potential revenue of seaweed production and biorefinery systems by compiling a product portfolio of high-value extract products. An investigation into the endogenous rhythms and extrinsic factors that impact the biomolecular composition of S. latissima is presented, and key performance factors for optimizing seaweed production are identified. Besides the provisioning ecosystem service, we highlight the contribution of green-engineered seaweed production systems to the mitigation of the ongoing and historical anthropogenic disturbances of the climate balance and nutrient flows. We conclude that there are risks of mismanagement, and we stress the importance and necessity of creating an adaptive ecosystem-based management framework within a triple-helix partnership for balancing the utilization of ecosystem services and long-term resilience of aquatic environment.

Caulerpa Cupressoides Var. Flabellata

Green seaweeds are rich sources of sulfated polysaccharides (SPs) with potential biomedical and nutraceutical applications. The aim of this work was to evaluate the immunostimulatory activity of SPs from the seaweed, Caulerpa cupressoides var. flabellata on murine RAW 264.7 macrophages. SPs were evaluated for their ability to modify cell viability and to stimulate the production of inflammatory mediators, such as nitric oxide (NO), intracellular reactive oxygen species (ROS), and cytokines. Additionally, their effect on inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) gene expression was investigated. The results showed that SPs were not cytotoxic and were able to increase in the production of NO, ROS and the cytokines, tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). It was also observed that treatment with SPs increased iNOS and COX-2 gene expression. Together, these results indicate that C. cupressoides var. flabellata SPs have strong immunostimulatory activity, with potential biomedical applications.

Gazing at Cell Wall Expansion under a Golden Light

In plants, cell growth is constrained by a stiff cell wall, at least this is the way textbooks usually present it. Accordingly, many studies have focused on the elasticity and plasticity of the cell wall as prerequisites for expansion during growth. With their specific evolutionary history, cell wall composition, and environment, brown algae present a unique configuration offering a new perspective on the involvement of the cell wall, viewed as an inert material yet with intrinsic mechanical properties, in growth. In light of recent findings, we explore here how much of the functional relationship between cell wall chemistry and intrinsic mechanics on the one hand, and growth on the other hand, has been uncovered in brown algae.

Enzymatic synthesis of l-fucose from l-fuculose using a fucose isomerase from Raoultella sp. and the biochemical and structural analyses of the enzyme

BACKGROUND

l-Fucose is a rare sugar with potential uses in the pharmaceutical, cosmetic, and food industries. The enzymatic approach using l-fucose isomerase, which interconverts l-fucose and l-fuculose, can be an efficient way of producing l-fucose for industrial applications. Here, we performed biochemical and structural analyses of l-fucose isomerase identified from a novel species of Raoultella (RdFucI).

RESULTS

RdFucI exhibited higher enzymatic activity for l-fuculose than for l-fucose, and the rate for the reverse reaction of converting l-fuculose to l-fucose was higher than that for the forward reaction of converting l-fucose to l-fuculose. In the equilibrium mixture, a much higher proportion of l-fucose (~ ninefold) was achieved at 30 °C and pH 7, indicating that the enzyme-catalyzed reaction favors the formation of l-fucose from l-fuculose. When biochemical analysis was conducted using l-fuculose as the substrate, the optimal conditions for RdFucI activity were determined to be 40 °C and pH 10. However, the equilibrium composition was not affected by reaction temperature in the range of 30 to 50 °C. Furthermore, RdFucI was found to be a metalloenzyme requiring Mn²⁺ as a cofactor. The comparative crystal structural analysis of RdFucI revealed the distinct conformation of α7-α8 loop of RdFucI. The loop is present at the entry of the substrate binding pocket and may affect the catalytic activity.

CONCLUSIONS

RdFucI-catalyzed isomerization favored the reaction from l-fuculose to l-fucose. The biochemical and structural data of RdFucI will be helpful for the better understanding of the molecular mechanism of l-FucIs and the industrial production of l-fucose.

Evolutionary Evidence of Algal Polysaccharide Degradation Acquisition by Pseudoalteromonas carrageenovora 9T to Adapt to Macroalgal Niches

About half of seaweed biomass is composed of polysaccharides. Most of these complex polymers have a marked polyanionic character. For instance, the red algal cell wall is mainly composed of sulfated galactans, agars and carrageenans, while brown algae contain alginate and fucose-containing sulfated polysaccharides (FCSP) as cell wall polysaccharides. Some marine heterotrophic bacteria have developed abilities to grow on such macroalgal polysaccharides. This is the case of Pseudoalteromonas carrageenovora 9^T (ATCC 43555^T), a marine gammaproteobacterium isolated in 1955 and which was an early model organism for studying carrageenan catabolism. We present here the genomic analysis of P. carrageenovora. Its genome is composed of two chromosomes and of a large plasmid encompassing 109 protein-coding genes. P. carrageenovora possesses a diverse repertoire of carbohydrate-active enzymes (CAZymes), notably specific for the degradation of macroalgal polysaccharides (laminarin, alginate, FCSP, carrageenans). We confirm these predicted capacities by screening the growth of P. carrageenovora with a large collection of carbohydrates. Most of these CAZyme genes constitute clusters located either in the large chromosome or in the small one. Unexpectedly, all the carrageenan catabolism-related genes are found in the plasmid, suggesting that P. carrageenovora acquired its hallmark capacity for carrageenan degradation by horizontal gene transfer (HGT). Whereas P. carrageenovora is able to use lambda-carrageenan as a sole carbon source, genomic and physiological analyses demonstrate that its catabolic pathway for kappa- and iota-carrageenan is incomplete. This is due to the absence of the recently discovered 3,6-anhydro-D-galactosidase genes (GH127 and GH129 families). A genomic comparison with 52 Pseudoalteromonas strains confirms that carrageenan catabolism has been recently acquired only in a few species. Even though the loci for cellulose biosynthesis and alginate utilization are located on the chromosomes, they were also horizontally acquired. However, these HGTs occurred earlier in the evolution of the Pseudoalteromonas genus, the cellulose- and alginate-related loci being essentially present in one large, late-diverging clade (LDC). Altogether, the capacities to degrade cell wall polysaccharides from macroalgae are not ancestral in the Pseudoalteromonas genus. Such catabolism in P. carrageenovora resulted from a succession of HGTs, likely allowing an adaptation to the life on the macroalgal surface.

Discovery and screening of novel metagenome-derived GH107 enzymes targeting sulfated fucans from brown algae

Sulfated fucans, often denoted as fucoidans, are highly variable cell wall polysaccharides of brown algae, which possess a wide range of bioactive properties with potential pharmaceutical applications. Due to their complex architecture, the structures of algal fucans have until now only been partly determined. Enzymes capable of hydrolyzing sulfated fucans may allow specific release of defined bioactive oligosaccharides and may serve as a tool for structural elucidation of algal walls. Currently, such enzymes include only a few hydrolases belonging to the glycoside hydrolase family 107 (GH107), and little is known about their mechanistics and the substrates they degrade. In this study, we report the identification and recombinant production of three novel GH107 family proteins derived from a marine metagenome. Activity screening against a large substrate collection showed that all three enzymes degraded sulfated fucans from brown algae in the order Fucales. This is in accordance with a hydrolytic activity against α-1,4-fucosidic linkages in sulfated fucans as reported for previous GH107 members. Also, the activity screening gave new indications about the structural differences in brown algal cell walls. Finally, sequence analyses allowed identification of the proposed catalytic residues of the GH107 family. The findings presented here form a new basis for understanding the GH107 family of enzymes and investigating the complex sulfated fucans from brown algae. DATABASE: The assembled metagenome and raw sequence data is available at EMBL-EBI (Study number: PRJEB28480). Sequences of the GH107 fucanases (Fp273, Fp277, and Fp279) have been deposited in GenBank under accessions MH755451-MH755453.

Algal Polysaccharides as Therapeutic Agents for Atherosclerosis

Seaweed-derived polysaccharides including agar and alginate, have found widespread applications in biomedical research and medical therapeutic applications including wound healing, drug delivery, and tissue engineering. Given the recent increases in the incidence of diabetes, obesity and hyperlipidemia, there is a pressing need for low cost therapeutics that can economically and effectively slow the progression of atherosclerosis. Marine polysaccharides have been consumed by humans for millennia and are available in large quantities at low cost. Polysaccharides such as fucoidan, laminarin sulfate and ulvan have shown promise in reducing atherosclerosis and its accompanying risk factors in animal models. However, others have been tested in very limited context in scientific studies. In this review, we explore the current state of knowledge for these promising therapeutics and discuss the potential and challenges of using seaweed derived polysaccharides as therapies for atherosclerosis.

Fucoidan Sulfatases from Marine Bacterium Wenyingzhuangia fucanilytica CZ1127T

Fucoidans belong to a structurally heterogeneous class of sulfated polysaccharides isolated from brown algae. They have a wide spectrum of biological activities. The complex structures of these polysaccharides hinder structure-activity relationships determination. Fucoidan sulfatases can make useful tools for the determination of the fine chemical structure of fucoidans. In this study, identification and preparation of two recombinant sulfatases able to catalyze the cleavage of sulfate groups from fragments of fucoidan molecules is described for the first time. Two genes of sulfatases swf1 and swf4 of the marine bacterium Wenyingzhuangia fucanilytica CZ1127^T were cloned and the proteins were produced in Escherichia coli cells. Sulfatases SWF1 and SWF4 are assigned to S1_17 and S1_25 subfamilies of formylglycine-dependent enzymes of S1 family (SulfAtlas). Some molecular and biochemical characteristics of recombinant fucoidan sulfatases have been studied. Detailed specificity and catalytic features of sulfatases were determined using various sulfated fucooligosaccharides. Structures of products produced by SWF1 and SWF4 were established by nuclear magnetic resonance (NMR) spectroscopy. Based on the obtained data, the enzymes are classified as fucoidan exo-2O-sulfatase (SWF1) and fucoidan exo-3O-sulfatase (SWF4). In addition, we demonstrated the sequential action of sulfatases on 2,3-di-O-sulfated fucooligosacchrides, which indicates an exolitic degradation pathway of fucoidan by a marine bacterium W. fucanilytica CZ1127^T.

Structure and Bioactivity Screening of a Low Molecular Weight Ulvan from the Green Alga Ulothrix flacca

A water-soluble low molecular–weight polysaccharide named UP2-1 was isolated and purified from the marine green algae Ulothrixflacca using ion-exchange and size-exclusion chromatography. Composition and characteristics analyses showed that UP2-1 was a sulfated glucuronorhamnan consisting of rhamnose and glucuronic acid in a ratio of 2:1 with 21% sulfate content and a molecular weight of 5.0 kDa. Structural properties were determined using desulfation and methylation analyses combined with infrared spectrum (IR), gas chromatography-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR). The results showed that UP2-1 was a type of ulvan composed of alternate 4-linked-α-L-rhamnose residues (→4)-α-L-Rha(1→) and 4-linked-β-D-glucouronoc acid residues. The sulfate groups were mainly present in the O-3 position of →4)-α-L-Rha(1→. Most (70%) of the rhamnose was sulfated. UP2-1 also had a small amount of →4)-α-L-Rha(1→ branch at the O-2 position of the →4)-α-L-Rha(1→. UP2-1 exhibited significant anticoagulant and immunomodulating activity in vitro. This study demonstrated that the green algae Ulothrix flacca, which is used as a food and traditional marine herb in China, could also be considered as a source of bioactive ulvan.

Biotechnology Potential of Marine Fungi Degrading Plant and Algae Polymeric Substrates

Filamentous fungi possess the metabolic capacity to degrade environment organic matter, much of which is the plant and algae material enriched with the cell wall carbohydrates and polyphenol complexes that frequently can be assimilated by only marine fungi. As the most renewable energy feedstock on the Earth, the plant or algae polymeric substrates induce an expression of microbial extracellular enzymes that catalyze their cleaving up to the component sugars. However, the question of what the marine fungi contributes to the plant and algae material biotransformation processes has yet to be highlighted sufficiently. In this review, we summarized the potential of marine fungi alternatively to terrestrial fungi to produce the biotechnologically valuable extracellular enzymes in response to the plant and macroalgae polymeric substrates as sources of carbon for their bioconversion used for industries and bioremediation.

Glucofucogalactan, a heterogeneous low-sulfated polysaccharide from Saccharina japonica and its bioactivity

Crude polysaccharide obtained from Saccharina japonica using acid hydrolysis and precipitation was separated into sulfated fuco-oligosaccharide (HDF1) and heteropolysaccharide (HDF2). To further explore the bioactive fraction, HDF2 was successfully separated using membrane filtration into HDF2A and HDF2B, which differed in chemical composition and molecular weight. The bioactivity of all the fractions was tested in vitro, including immunomodulatory activity in RAW 264.7 cells and the protective activity in aristolochic acid (AA)-induced NRK-52E cell injury. HDF1 and HDF2B (low-molecular weight sulfated fucans/fuco-oligosaccharides) did not increase the nitric oxide production in RAW 264.7 cells, whereas HDF2 and HDF2A exhibited potential immunomodulatory activity. All the tested compounds showed different degrees of protective activity in AA-induced injury; HDF2A exhibited superior protective activity. Through chemical analysis, HPLC analysis, and IR spectroscopy and MS, it was determined that HDF2A was a galactose-enriched heteropolysaccharide- glucofucogalactan with a distinctive 2:1 ratio of galactose to fucose. In addition, HDF2A also contained a high amount of glucose and minor amounts of mannose, rhamnose, and xylose, with a low content of sulfate. Thus, HDF2A, a complex heterogeneous polysaccharide mixture with a unique monosaccharide composition, could be studied for further structural characterization and pharmaceutical applications.

Update on Marine Carbohydrate Hydrolyzing Enzymes: Biotechnological Applications

After generating much interest in the past as an aid in solving structural problems for complex molecules such as polysaccharides, carbohydrate-hydrolyzing enzymes of marine origin still appear as interesting biocatalysts for a range of useful applications in strong interdisciplinary fields such as green chemistry and similar domains. The multifaceted fields in which these enzymes are of interest and the scarce number of original articles in literature prompted us to provide the specialized analysis here reported. General considerations from modern (2016-2017 interval time) review articles are at start of this manuscript; then it is subsequently organized in sections according to particular biopolymers and original research articles are discussed. Literature sources like the Science Direct database with an optimized W/in search, and the Espacenet patent database were used.

Double blind microarray-based polysaccharide profiling enables parallel identification of uncharacterized polysaccharides and carbohydrate-binding proteins with unknown specificities

Marine algae are one of the largest sources of carbon on the planet. The microbial degradation of algal polysaccharides to their constitutive sugars is a cornerstone in the global carbon cycle in oceans. Marine polysaccharides are highly complex and heterogeneous, and poorly understood. This is also true for marine microbial proteins that specifically degrade these substrates and when characterized, they are frequently ascribed to new protein families. Marine (meta)genomic datasets contain large numbers of genes with functions putatively assigned to carbohydrate processing, but for which empirical biochemical activity is lacking. There is a paucity of knowledge on both sides of this protein/carbohydrate relationship. Addressing this 'double blind' problem requires high throughput strategies that allow large scale screening of protein activities, and polysaccharide occurrence. Glycan microarrays, in particular the Comprehensive Microarray Polymer Profiling (CoMPP) method, are powerful in screening large collections of glycans and we described the integration of this technology to a medium throughput protein expression system focused on marine genes. This methodology (Double Blind CoMPP or DB-CoMPP) enables us to characterize novel polysaccharide-binding proteins and to relate their ligands to algal clades. This data further indicate the potential of the DB-CoMPP technique to accommodate samples of all biological sources.