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Algal carbohydrates: Sources, biosynthetic pathway, production, and applications
... These compounds are of interest for use in the production of biofuels and bioplastics, which offer sustainable alternatives to conventional materials. In addition, the ability of some microalgae to modulate carbohydrate synthesis under different environmental conditions makes them ideal candidates for the production of bioenergy and high value-added bioproducts [184,185]. ...
The growing demand for sustainable production of high-value compounds, such as biofuels, lipids, and pigments like carotenoids and phycobilin, has become the subject of numerous investigations. Furthermore, this fact has led to the exploration of re-newable methods utilizing microalgae as feedstock to mitigate the challenges associ-ated with producing these valuable compounds. Nevertheless, despite the numerous advantages of microalgae, the development of a microalgal biorefinery that employs sustainable, environmentally friendly, and economically efficient technologies remains a necessity. To address this challenge, the bio-flocculation process and more specially the self-flocculation ability, is presented as a cost-effective and energy-efficient solu-tion. This method is as easy and effective as chemical flocculation, which is applied at industrial scale, however in contrast, it is sustainable and cost-effective as no costs are involved for pre-treatment of the biomass for oil extraction and for pre-treatment of the medium before it can be re-used. In addition, microalgae possess molecular tools that would allow increasing the efficiency of these processes. In the present review, we summarize microalgal harvesting technologies, with a particular focus on bio- and self-flocculation processes and identify the improvement technologies that could en-hance the production of high added-value compounds while simultaneously reducing costs in microalgae biorefinery.
... Agar is a kind of seaweed polysaccharide with gelatinizing ability and is mainly extracted from the Gracilariaceae and Gelidiaceae families [23]. Currently, agar is used in a wide range of applications, including food, pharmaceuticals, nutraceuticals, and biomedical applications [24]. When the agar solution is cooled, the agar molecules change from a linear to a double-helical shape, forming a stable three-dimensional network structure with increased hydrogen bonds. ...
To reduce the risk of adsorption of granular activated carbon (AC) in the gastrointestinal tract, we successfully prepared a hollow-type spherical bacterial cellulose gel encapsulated with AC (ACEG) and evaluated its pH tolerance and adsorption capacity. The bacterial cellulose gel membrane of ACEG features a three-dimensional mesh structure of cellulose fibers, allowing the selective permeation of substances based on their size. In this study, the preparation method of ACEGs was investigated, and the indole saturation adsorption capacity of the obtained gel was measured. We modified the gel culture nucleus gel from calcium alginate gel to agar gel, facilitating the encapsulation of previously challenging particles. The new preparation method used sodium hydroxide solution for sterilization and dissolution to remove the debris of Komagataeibacter xylinus, which was feared to remain in the bacterial cellulose membrane. This treatment was also confirmed to have no effect on the adsorption capacity of the AC powder. Therefore, this new preparation method is expected not only to improve the performance of ACEGs but also to be applied to a wide range of adsorbent-encapsulated hollow-type bacterial cellulose gels.
Glycogen serves as a metabolic sink in cyanobacteria. Glycogen deficiency causes the extracellular release of distinctive metabolites such as pyruvate and 2-oxoglutarate upon nitrogen depletion; however, the mechanism has not been fully elucidated. This study aimed to elucidate the mechanism of carbon partitioning in glycogen-deficient cyanobacteria. Extracellular and intracellular metabolites in a glycogen-deficient ΔglgC mutant of Synechococcus elongatus PCC 7942 were comprehensively analyzed. In the presence of a nitrogen source, the ΔglgC mutant released extracellular glutamate rather than pyruvate and 2-oxoglutarate, whereas its intracellular glutamate level was lower than that in the wild-type strain. The de novo synthesis of glutamate increased in the ΔglgC mutant, suggesting that glycogen deficiency enhanced carbon partitioning into glutamate and extracellular excretion through an unidentified transport system. This study proposes a model in which glutamate serves as the prime extracellular metabolic sink alternative to glycogen when nitrogen is available.
The marine environment, contains plentiful renewable resources, e.g. macroalgae with unique polysaccharides, motivating search for enzymes from marine microorganisms to explore conversion possibilities of the polysaccharides. In this study, the first GH17 glucanosyltransglycosylase, MlGH17B, from a marine bacterium (Muricauda lutaonensis), was characterized. The enzyme was moderately thermostable with Tm at 64.4 °C and 73.2 °C, but an activity optimum at 20 °C, indicating temperature sensitive active site interactions. MlGH17B uses β-1,3 laminari-oligosaccharides with a degree of polymerization (DP) of 4 or higher as donors. Two glucose moieties (bound in the aglycone +1 and +2 subsites) are cleaved off from the reducing end of the donor while the remaining part (bound in the glycone subsites) is transferred to an incoming β-1,3 glucan acceptor, making a β-1,6-linkage, thereby synthesizing branched or kinked oligosaccharides. Synthesized oligosaccharides up to DP26 were detected by mass spectrometry analysis, showing that repeated transfer reactions occurred, resulting in several β-1,6-linked branches. The modeled structure revealed an active site comprising five subsites: three glycone (−3, −2 and −1) and two aglycone (+1 and +2) subsites, with significant conservation of substrate interactions compared to the only crystallized 1,3-β-glucanosyltransferase from GH17 (RmBgt17A from the compost thriving fungus Rhizomucor miehei), suggesting a common catalytic mechanism, despite different phylogenetic origin, growth environment, and natural substrate. Both enzymes lacked the subdomain extending the aglycone subsites, found in GH17 endo-β-glucanases from plants, but this extension was also missing in bacterial endoglucanases (modeled here), showing that this feature does not distinguish transglycosylation from hydrolysis, but may rather relate to phylogeny.
Laminarin, a complicated polysaccharide originating from brown algae, has emerged as a compelling candidate in the domain of biomedical research. This enigmatic molecule, composed of glucose units associated with both β-1,3 and β-1,6 glycosidic bonds, possesses an array of remarkable characteristics that render it auspicious for multifaceted biomedical applications. This review investigates the comprehensive potential of laminarin in the biomedical domain, emphasizing its remarkable biocompatibility, low cytotoxicity, and cell proliferation support. Laminarin's immunomodulatory attributes position it as an encouraging contender in immunotherapy and the development of vaccines. Moreover, its anti-inflammatory and antioxidant characteristics provide a promising avenue for combatting conditions associated with oxidative stress. In particular, laminarin excels as a drug delivery vehicle owing to its exceptional encapsulation capabilities emerging from its porous framework. Integrating pH and redox responsiveness in laminarin-based drug delivery systems is poised to redefine targeted therapies. Laminarin substantially contributes to tissue engineering by improving adhesion, migration of cells, and deposition of extracellular matrix. This augmentation magnifies the regenerative capability of tissue-engineered constructs, substantiated by the advancement of laminarin-based wound dressings and tissue scaffolds, marking considerable progress in the domain of wound healing and tissue regeneration. While laminarin exhibits substantial potential in biomedical applications, it remains in the initial phases of exploration. Comprehensive preclinical and clinical research is warranted to verify its effectiveness and safety across various applications. In essence, laminarin, a marine marvel, has the capability to remodel biomedical research, offering inventive solutions to complex difficulties.
Generally wastewater such agricultural runoff is considered a nuisance; however, it could be harnessed as a potential source of nutrients like nitrates and phosphates in integrated biorefinery context. In the current study, microalgae Chlorella sp. S5 was used for bioremediation of agricultural runoff and the leftover algal biomass was used as a potential source for production of biofuels in an integrated biorefinery context. The microalgae Chlorella sp. S5 was cultivated on Blue Green (BG 11) medium and a comprehensive optimization of different parameters including phosphates , nitrates, and pH was carried out to acquire maximum algal biomass enriched with high lipids content. Dry biomass was quantified using the solvent extraction technique, while the identification of nitrates and phosphates in agricultural runoff was carried out using commercial kits. The algal extracted lipids (oils) were employed in enzy-matic trans-esterification for biodiesel production using whole-cell biomass of Bacillus subtilis Q4 MZ841642. The resultant fatty acid methyl esters (FAMEs) were analyzed using Fourier transform infrared (FTIR) spectroscopy and gas chromatography coupled with mass spectrometry (GC-MS). Subsequently, both the intact algal biomass and its lipid-depleted algal biomass were used for biogas production within a batch anaerobic digestion setup. Interestingly, Chlorella sp. S5 demonstrated a substantial reduction of 95% in nitrate and 91% in phosphate from agricultural runoff. The biodiesel derived from algal biomass exhibited a noteworthy total FAME content of 98.2%, meeting the quality standards set by American Society for Testing and Materials (ASTM) and European union (EU) standards. Furthermore , the biomethane yields obtained from whole biomass and lipid-depleted biomass were 330.34 NmL/g VS added and 364.34 NmL/g VS added , respectively. In conclusion, the findings underscore the potent utility of Chlorella sp. S5 as a multi-faceted resource, proficiently employed in a sequential cascade for treating agricultural runoff, producing biodiesel, and generating biogas within the integrated biorefinery concept.
Microalgae, capable of accumulating large amounts of lipids, are of great value for biodiesel production. The high cost of such production stimulates the search for cultivation conditions that ensure their highest productivity. Reducing the content of nitrogen and phosphorus in the culture medium is widely used to change the content and productivity of lipids in microalgae. Achieving the right balance between maximum growth and maximum lipid content and productivity is the primary goal of many experimental works to ensure cost-effective biodiesel production from microalgae. The content of nitrogen and phosphorus in nutrient media for algal cultivation after converted to nitrogen (-N) and phosphorus (-P) lies in an extensive range: from 0.007 g L− 1 to 0.417 g L− 1 and from 0.0003 g L− 1 to 0.227 g L− 1 and N:P ratio from 0.12:1 to 823.33:1. When studying nutritional stress in microalgae, no single approach is used to determine the experimental concentrations of nitrogen and phosphorus. This precludes the possibility of correct interpretation of the data and may lead to erroneous conclusions. This work results from the systematisation of information on using nitrogen and phosphorus restriction to increase the lipid productivity of microalgae of different taxonomic and ecological groups to identify future research directions. The results of 301 experiments were included in the analysis using the principal components method. The investigation considered various divisions and classes: Cyanobacteria, Rhodophyta, Dinophyta, Haptophyta, Cryptophyta, Heterokontophyta/Ochrophyta (Bacillariophyceae, Eustigmatophyceae, Xanthophyceae), Chlorophyta, and also the ratio N:P, the time of the experiment, the light intensity during cultivation. Based on the concentrations of nitrogen and phosphorus existing in various nutrient media, a general scheme for designating the supply of nutrient media for nitrogen (as NO3⁻ or NH4+, N g L− 1) and phosphorus (as РO4⁻, P g L− 1) has been proposed: replete -N (˃0.4 g L− 1), moderate -N (0.4–0.2), moderate N-limitation (0.19–0.1), strong N-limitation (˂0.1), without nitrogen (0), replete -Р (˃0.2), moderate -P (0.2–0.02), moderate P-limitation (0.019–0.01), strong P-limitation (˂0.01), without phosphorus (0).
Supplementary Information
The online version contains supplementary material available at 10.1186/s12934-023-02244-6.
Fucoidans are sulfate-rich polysaccharides with a wide variety of beneficial biological activities. The present study aimed to highlight the anti-inflammatory activity of fucoidan from the brown seaweed Sargassum autumnale (SA) against lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells. Among the isolated fucoidan fractions, the third fraction (SAF3) showed a superior protective effect on LPS-stimulated RAW 264.7 cells. SAF3 inhibits nitric oxide (NO) production and expression of prostaglandin E-2 (PGE2) via downregulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2) expression in LPS-induced RAW 26.7 cells. SAF3 treatment decreased pro-inflammatory cytokines IL-1β, TNF-α, and IL-6 expression in LPS-induced cells. LPS stimulation activated NF-κB and MAPK signaling cascades in RAW 264.7 cells, while treatment with SAF3 suppressed them in a concentration-dependent manner. Existing outcomes confirm that SAF3 from S. autumnale possesses potent anti-inflammatory activity and exhibits good potential for application as a functional food ingredient or for the treatment of inflammation-related disorders.
Numerous compounds present in the ocean are contributing to the development of the biomedical field. Agarose, a polysaccharide derived from marine red algae, plays a vital role in biomedical applications because of its reversible temperature-sensitive gelling behavior, excellent mechanical properties, and high biological activity. Natural agarose hydrogel has a single structural composition that prevents it from adapting to complex biological environments. Therefore, agarose can be developed into different forms through physical, biological, and chemical modifications, enabling it to perform optimally in different environments. Agarose biomaterials are being increasingly used for isolation, purification, drug delivery, and tissue engineering, but most are still far from clinical approval. This review classifies and discusses the preparation, modification, and biomedical applications of agarose, focusing on its applications in isolation and purification, wound dressings, drug delivery, tissue engineering, and 3D printing. In addition, it attempts to address the opportunities and challenges associated with the future development of agarose-based biomaterials in the biomedical field. It should help to rationalize the selection of the most suitable functionalized agarose hydrogels for specific applications in the biomedical industry.
Introduction:
Ulva lactuca polysaccharide (ULP) is green algae extract with numerous biological activities, including anticoagulant, anti-inflammatory, and antiviral effects. However, the inhibitory ability of ULP in the development of hepatocellular carcinoma warrants further studies.
Objectives:
To elucidate the anti-tumor mechanism of ULP action and evaluate its regulatory effect on gut microbiota and metabolism in H22 hepatocellular carcinoma tumor-bearing mice.
Methods:
An H22 tumor-bearing mouse model was established by subcutaneously injecting H22 hepatoma cells. The gut microbiota composition in cecal feces was assessed and subjected to untargeted metabolomic sequencing. The antitumor activity of ULP was verified further by western blot, RT-qPCR, and reactive oxygen species (ROS) assays.
Results:
Administration of ULP alleviated tumor growth by modulating the compositions of the gut microbial communities (Tenericutes, Agathobacter, Ruminiclostridium, Parabacteroides, Lactobacillus, and Holdemania) and metabolites (docosahexaenoic acid, uric acid, N-Oleoyl Dopamine, and L-Kynurenine). Mechanistically, ULP promoted ROS production by inhibiting the protein levels of JNK, c-JUN, PI3K, Akt, and Bcl-6, thereby delaying the growth of HepG2 cells.
Conclusion:
ULP attenuates tumor growth in H22 tumor-bearing mice by modulating gut microbial composition and metabolism. ULP inhibits tumor growth mainly by promoting ROS generation.
Brown algae annually convert gigatons of carbon dioxide into carbohydrates, including the complex extracellular matrix polysaccharide fucoidan. Due to its persistence in the environment, fucoidan is potentially a pathway for marine carbon sequestration. Rates of fucoidan secretion by brown algae remain unknown due to the challenge of identifying and quantifying complex polysaccharides in seawater. We adapted the techniques of anion exchange chromatography, enzyme-linked immunosorbent assay, and biocatalytic enzyme-based assay for detection and quantification of fucoidan. We found the brown alga Fucus vesiculosus at the Baltic Sea coast of south-west Finland to secrete 0.3% of their biomass as fucoidan per day. Dissolved fucoidan concentrations in seawater adjacent to algae reached up to 0.48 mg L-1. Fucoidan accumulated during incubations of F. vesiculosus, significantly more in light than in darkness. Maximum estimation by acid hydrolysis indicated fucoidan secretion at a rate of 28 to 40 mg C kg-1 h-1, accounting for 44 to 50% of all exuded dissolved organic carbon. Composed only of carbon, oxygen, hydrogen, and sulfur, fucoidan secretion does not consume nutrients enabling carbon sequestration independent of algal growth. Extrapolated over a year, the algae sequester more carbon into secreted fucoidan than their biomass. The global utility of fucoidan secretion is an alternative pathway for carbon dioxide removal by brown algae without the need to harvest or bury algal biomass.
Marine algal species comprise of a large portion of polysaccharides which have shown multifunctional properties and health benefits for treating and preventing human diseases. Laminarin, or β-glucan, a storage polysaccharide from brown algae, has been reported to have potential pharmacological properties such as antioxidant, anti-tumor, anti-coagulant, anticancer, immunomodulatory, anti-obesity, anti-diabetic, anti-inflammatory, wound healing, and neuroprotective potential. It has been widely investigated as a functional material in biomedical applications as it is biodegradable, biocompatible, and is low toxic substances. The reported preclinical and clinical studies demonstrate the potential of laminarin as natural alternative agents in biomedical and industrial applications such as nutraceuticals, pharmaceuticals, functional food, drug development/delivery, and cosmeceuticals. This review summarizes the biological activities of laminarin, including mechanisms of action, impacts on human health, and reported health benefits. Additionally, this review also provides an overview of recent advances and identifies gaps and opportunities for further research in this field. It further emphasizes the molecular characteristics and biological activities of laminarin in both preclinical and clinical settings for the prevention of the diseases and as potential therapeutic interventions.
The marine macroalgae produce a collection of bioactive polysaccharides, of which the sulfated heteropolysaccharide fucoidan produced by brown algae of the class Phaeophyceae has received worldwide attention because of its particular biological actions that confer nutritional and health benefits to humans and animals. The biological actions of fucoidan are determined by their structure and chemical composition, which are largely influenced by the geographical location, harvest season, extraction process, etc. This review discusses the structure, chemical composition and physicochemical properties of fucoidan. The biological action of fucoidan and its applications for human health, tissue engineering, regenerative medicine and drug delivery are also addressed. The industrial scenario and prospects of research depicted would give an insight into developing fucoidan as a commercially viable and sustainable bioactive material in the nutritional and pharmacological sectors.
The rapid expansion of both the global economy and the human population has led to a shortage of water resources suitable for direct human consumption. As a result, water remediation will inexorably become the primary focus on a global scale. Microalgae can be grown in various types of wastewaters (WW). They have a high potential to remove contaminants from the effluents of industries and urban areas. This review focuses on recent advances on WW remediation through microalgae cultivation. Attention has already been paid to microalgae-based wastewater treatment (WWT) due to its low energy requirements, the strong ability of microalgae to thrive under diverse environmental conditions, and the potential to transform WW nutrients into high-value compounds. It turned out that microalgae-based WWT is an economical and sustainable solution. Moreover, different types of toxins are removed by microalgae through biosorption, bioaccumulation, and biodegradation processes. Examples are toxins from agricultural runoffs and textile and pharmaceutical industrial effluents. Microalgae have the potential to mitigate carbon dioxide and make use of the micronutrients that are present in the effluents. This review paper highlights the application of microalgae in WW remediation and the remediation of diverse types of pollutants commonly present in WW through different mechanisms, simultaneous resource recovery, and efficient microalgae-based co-culturing systems along with bottlenecks and prospects.
Red algae Gracilaria is one of the most cultivated seaweeds and a major source of agar in the world. Gracilaria demonstrates easy propagation, high growth rates, and tolerance to a broad range of salinities. Agar usage is related to thermo-reversible gels formation at low concentrations in water with wide applications in food, pharmaceutical, medical, engineering, agricultural and other fields. In this work, we analyzed and compared agar content of the estuarine seaweed Gracilaria sp. grown in two distinct cultivation methods: (1) inshore tank cultivation technique and (2) indoor cultivation technique using different mediums (seawater and brackish water) to get a better understanding about the best medium for large scale sustainable cultivation in the future; wild Gracilaria sp. samples were used as control. Inshore tank cultivation exhibited the highest agar extraction yield (20.67±0.27%) when compared with the control (16.67±2.72%); indoor cultivation using brackish water medium (13.8±1.5%) and seawater medium (11.64±2.38%) revealed lower values than the control, but still promising for large scale cultivation and agar exploitation.
Whole-cell microalgae biomass and their specific metabolites are excellent sources of renewable and alternative feedstock for various products. In most cases, the content and quality of whole-cell biomass or specific microalgal metabolites could be produced by both fresh and marine microalgae strains. However, a large water footprint for freshwater microalgae strain is a big concern, especially if the biomass is intended for non-food applications. Therefore, if any marine microalgae could produce biomass of desired quality, it would have a competitive edge over freshwater microalgae. Apart from biofuels, recently, microalgal biomass has gained considerable attention as food ingredients for both humans and animals and feedstock for different bulk chemicals. In this regard, several technologies are being developed to utilize marine microalgae in the production of food, feed, and biofuels. Nevertheless, the production of suitable and cheap biomass feedstock using marine microalgae has faced several challenges associated with cultivation and downstream processing. This review will explore the potential pathways, associated challenges, and future directions of developing marine microalgae biomass-based food, feed, and fuels (3F).
Agar is widely applied across the food, pharmaceutical and biotechnology industries, owing to its various bioactive functions. To better understand the agar biosynthesis in commercial seaweed Gracilariopsis lemaneiformis, the activities of four enzymes participating in the agar biosynthesis were detected, and phosphoglucomutase (PGM) was confirmed as highly correlated with agar accumulation. Three genes of PGM (GlPGM1, GlPGM2 and GlPGM3) were identified from the G. lemaneiformis genome. The subcellular localization analysis validated that GlPGM1 was located in the chloroplast and GlPGM3 was not significantly distributed in the organelles. Both the GlPGM1 and GlPGM3 protein levels showed a remarkable consistency with the agar variations, and GlPGM3 may participate in the carbon flux between (iso)floridoside, floridean starch and agar synthesis. After treatment with the PGM inhibitor, the agar and floridean starch contents and the activities of floridean starch synthase were significantly decreased; products identified in the Calvin cycle, pentose phosphate pathway, the Embden-Meyerhof-Parnas pathway and the tricarboxylic acid cycle were depressed; however, lipids, phenolic acids and the intermediate metabolites, fructose-1,6-phosphate were upregulated. These findings reveal the essential role of PGM in regulating the carbon flux between agar and other carbohydrates in G. lemaneiformis, providing a guide for the artificial regulation of agar accumulation.
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.
Microalgae and cyanobacteria are photosynthetic organisms that can produce/accumulate biomolecules with industrial interest. Among these molecules, EPSs are macromolecular polysaccharidic compounds that present biological activities and physico-chemical properties, allowing to consider their valorization in diverse commercial markets, such as cosmetic, therapeutic, nutraceutic, or hydrocolloids areas. The number of microalgae and cyanobacteria strains described to produce such EPSs has increased in recent years as, among the 256 producing strains gathered in this review, 86 were published in the last 10 years (~33%). Moreover, with the rise of research on microalgae EPSs, a variety of monosaccharides compositions have been discovered, highlighting the versatility of these organisms. If some production strategies can be applied to increase EPS production yields, it appears that case by case studies are needed to promote EPS synthesis by a strain, as many responses exist. This paper proposes an up-to-date state of the art of the diversity of microalgae and cyanobacteria EPS-producing strains, associated to the variability of compositions. The strategies for the production and extraction of the polymers are also discussed. Finally, an overview of the biological activities and physico-chemical properties allow one to consider their use on several commercial markets.
Exopolysaccharides (EPSs) are high molecular weight polysaccharides secreted by microorganisms in the surrounding environment. In addition to the favorable benefits of these compounds for microorganisms, including microbial cell protection, they are used in various food, pharmaceutical, and cosmetic industries. Investigating the functional and health-promoting characteristics of microbial EPS, identifying the isolation method of these valuable compounds, and their applications in the food industry are the objectives of this study. EPS are used in food industries as thickeners, gelling agents, viscosifiers, and film formers. The antioxidative, anticancer, prebiotic, and cholesterol-lowering effects of some of these compounds make it possible to use them in functional food production.
Carrageenan is a polysaccharide derived from red algae (seaweed) with enormous economic potential in a wide range of industries, including pharmaceuticals, food, cosmetics, printing, and textiles. Carrageenan is primarily produced through aquaculture-based seaweed farming, with Eucheuma and Kappaphycus species accounting for more than 90% of global output. There are three major types of carrageenan found in red algae: kappa (κ)-, iota (ι)-, and lambda (λ)-carrageenan. Kappaphycus alvarezii is the most common kappa-carrageenan source, and it is primarily farmed in Asian countries such as Indonesia, the Philippines, Vietnam, and Malaysia. Carrageenan extracted from K. alvarezii has recently received a lot of attention due to its economic potential in a wide range of applications. This review will discuss K. alvarezii carrageenan in terms of metabolic and physicochemical structure, extraction methods and factors affecting production yield, as well as current and future applications.
Cell wall polysaccharides (CWPS) of seaweeds play crucial roles in mechanical shear resistance, cell-cell adhesion and the interactions with changeable marine environments. They have diverse applications in food, cosmetics, agriculture, pharmaceuticals and therapeutics. The recent boost of multi-omics sequence analysis has rapidly progressed the mining of presumed genes encoding enzymes involved in CWPS biosynthesis pathways. In this review, we summarize the biosynthetic pathways of alginate, fucoidan, agar, carrageenan and ulvan in seaweeds referred to the literatures on published genomes and biochemical characterization of encoded enzymes. Some transcriptomic data were briefly reported to discuss the correlation between gene expression levels and CWPS contents. Mannuronan C-5 epimerase (MC5E) and carbohydrate sulfotransferase (CST) are crucial enzymes for alginate and sulfated CWPS, respectively. Nonetheless, most CWPS-relevant genes were merely investigated by gene mining and phylogenetic analysis. We offer an integrative view of CWPS biosynthesis from a molecular perspective and discuss about the underlying regulation mechanism. However, a clear understanding of the relationship between chemical structure and bioactivities of CWPS is limited, and reverse genetic manipulation and effective gene editing tools need to be developed in future.
Hemicellulosic polysaccharides built of β‐1,4‐linked mannose units have been found throughout the plant kingdom and have numerous industrial applications. Here, I review recent advances in the biosynthesis and modification of plant β‐mannans. These matrix polymers can associate with cellulose bundles to impact the mechanical properties of plant fibers or biocomposites. In certain algae, mannan microfibrils even replace cellulose as the dominant structural component of the cell wall. Conversely, patterned galactoglucomannan found in Arabidopsis thaliana seed mucilage significantly modulates cell wall architecture and abiotic stress tolerance despite its relatively low content. I also discuss the subcellular requirements for β‐mannan biosynthesis, the increasing number of carbohydrate‐active enzymes involved in this process, and the players that continue to be puzzling. I discuss how cellulose synthase‐like enzymes elongate (gluco)mannans in orthogonal hosts and highlight the discoveries of plant enzymes that add specific galactosyl or acetyl decorations. Hydrolytic enzymes such as endo‐β‐1,4‐mannanases have recently been involved in a wide range of biological contexts including seed germination, wood formation, heavy metal tolerance, and defense responses. Synthetic biology tools now provide faster tracks to modulate the increasingly‐relevant mannan structures for improved plant traits and bioproducts.
Offshore aquaculture has the potential to expand the macroalgal industry. However, moving into deeper waters requires suspended structures that will present novel farm-environment interactions. Here, we present a computational modeling framework, the Macroalgal Cultivation Modeling System (MACMODS), to explore within-farm modifications to light, seawater flow, and nutrient fields across time and space scales relevant to macroalgae. A regional ocean model informs the site-specific setting, the Santa Barbara Channel in the Southern California Bight. A fine-scale hydrodynamic model predicts modified flows and turbulent mixing within the farm. A spatially resolved macroalgal growth model, parameterized for giant kelp, Macrocystis pyrifera, predicts kelp biomass. Key findings from model integration are that regional ocean conditions set overall farm performance, while fine-scale within-farm circulation and nutrient delivery are important to resolve variation in within-farm macroalgal performance. Therefore, we conclude that models resolving within-farm dynamics can provide benefit to farmers with insight on how farm design and regional ocean conditions interact to influence overall yield. Here, the presence of repeating longlines aligned with the mean current generate flow diversions around the farm as well as attached Langmuir circulations and increased turbulence intensity. These flow-induced phenomena lead to less biomass in the interior portion of the farm relative to the edges. We also find that there is an effluent “footprint” that extends as much as 20 km beyond the farm. In this regard, MACMODS can be used to not only evaluate farm design and cultivation practices that maximize yield but also explore interactions between the farm and ecosystem in order to minimize impacts.
Recent years, algal polysaccharides were mainly investigated for pharmaceutical, nutraceuticals and biomedical applications due to their promising bioactive properties. Moreover, it is now becoming a potential source for several non-medical and non-food applications in which biofuels are a major sector. The marine algae contain a variety of polysaccharides comprising 15–75% of dry biomass, including mucopolysaccharides, structured as well as storage polysaccharides. Industrial and dietary use of algal polysaccharide is on the rise, having an economic global impact. They have been industrially used as stabilizers, emulsifiers, thickeners, animal feed, foods and beverages, pharmaceuticals among others. Despite its low calorie and fat content, seaweed contains a significant amount of fiber (polysaccharide) that is beneficial to the digestive system. In industries for pharmaceuticals and biomedicine, alginates, fucoidans, ulvans, carrageenans, and chitin are becoming increasingly important. In fact, little research has been conducted on microalgal polysaccharides, linking their chemical structure with their biological activity. Moreover, with breakthrough technologies viable microalgal cultivation and improved carbohydrate production must be developed. Several studies highlighted the recent updates on microalgae, their key challenges in production and characterization of microalgal polysaccharides but lacking connection of chemical structure and functionality. The present review provides a brief summary of the key advances in the feasible production strategies of microalgal polysaccharides to make its extraction economically feasible, review on recent cost-effective extraction and purification methods. Moreover, analyzed structure divergence and tried to correlate their chemical structure with functionality prior to describing its broader potential beyond its existing applications.
Graphical abstract
Alginates are natural polysaccharides that are extracted from brown seaweed varieties and it is widely used for their rheological properties. The main step in the extraction protocol of sodium alginate is alkaline extraction. Sodium alginate was produced by dipping the seaweed in 1% formaldehyde and 2.5% of sodium carbonate solution and properties were studied following the standard methods. The amount of sodium alginate yield was 31.7% in Sargassum wightii. The moisture content and the ash content were recorded at 16.82% and 5.20%, respectively. The viscosity and the gel strength were noted as 40 vcP, 4.54 × 10–2 kN with 0.1 M CaCl2 and 6.86 × 10–2 kN with 0.2 M CaCl2 respectively. This study of the extraction method and its properties reveal that Sargassum wightii brown seaweed species have a high affinity to extract the alginate.
Botryococcus braunii, a prestigious energy microalga, has recently received widespread attention because it can secrete large amounts of exopolysaccharides (EPS) with potential applications in food, cosmetics, and nutraceuticals. Unfortunately, the insufficiency of research on the bioactivity and structure–activity relationship of B. braunii EPS has impeded the downstream applications. In the present study, alcohol precipitation, deproteinization, and DEAE-cellulose column chromatography were used to extract and purify B. braunii SCS-1905 EPS. It was found that B. braunii SCS-1905 EPS were high-molecular-weight heteropolysaccharides containing uronic acid (7.43–8.83%), protein (2.30–4.04%), and sulfate groups (1.52–1.95%). Additionally, the EPS primarily comprised galactose (52.34–54.12%), glucose (34.60–35.53%), arabinose (9.41–10.32%), and minor amounts of fucose (1.80–1.99%), with the presence of a pyranose ring linked by a β-configurational glycosidic bond. Notably, the antioxidant activity of crude exopolysaccharides (CEPS) was stronger, and the half maximal inhibitory concentration (IC50) for ABTS and hydroxyl radicals was significantly lower than that of deproteinized exopolysaccharides (DEPS). Overall, this study indicated a potential application of B. braunii SCS-1905 EPS as a natural antioxidant. In summary, B. braunii EPS could be used as a potential feedstock for the production of antioxidant health foods.
Algae are recognized as the main producer of commercial alginate. Alginate produced using algae is located in the walls and intracellular regions of their cells. Its properties vary depending on the species, growing and harvesting seasons, and extraction methods. Alginate has attracted the attention of several industries, thanks to its unique properties such as its biodegradability, biocompatibility, renewability and lack of toxicity features. For example, it is considered a good encapsulation agent due to the transparent nature of the alginate matrices. Also, this biopolymer is recognized as a functional food in the food industry. It can be tolerated easily in human body and has the ability to reduce the risk of chronic diseases. Besides, it is used as an abrasive agent, antioxidant, and thickening and stabilizing agents in cosmetic and pharmaceutic industries. Generally, it is used in emulsion systems and wound dressing patches. Furthermore, this polysaccharide has the potential to be used in green nanotechnologies as a drug delivery vehicle via cell microencapsulation. Moreover, it is suitable to adopt as a coagulant due to its wide range of flocculation dose and high shear stability. In this chapter, the mentioned usage areas of algal alginate are explained in more detail.
Brown algae (Phaeophyceae) have been consumed by humans for hundreds of years. Current studies have shown that brown algae are rich sources of bioactive compounds with excellent nutritional value, and are considered functional foods with health benefits. Polysaccharides are the main constituents of brown algae; their diverse structures allow many unique physical and chemical properties that help to moderate a wide range of biological activities, including immunomodulation, antibacterial, antioxidant, prebiotic, antihypertensive, antidiabetic, antitumor, and anticoagulant activities. In this review, we focus on the major polysaccharide components in brown algae: the alginate, laminarin, and fucoidan. We explore how their structure leads to their health benefits, and their application prospects in functional foods and pharmaceuticals. Finally, we summarize the latest developments in applied research on brown algae polysaccharides.
During the processes of primary and secondary endosymbiosis, different microalgae evolved to synthesis different storage polysaccharides. In stramenopiles, the main storage polysaccharides are β-1,3-glucan, or laminarin, in vacuoles. Currently, laminarin is gaining considerable attention due to its application in the food, cosmetic and pharmaceuticals industries, and also its importance in global biogeochemical cycles (especially in the ocean carbon cycle). In this review, the structures, composition, contents, and bioactivity of laminarin were summarized in different algae. It was shown that the general features of laminarin are species-dependence. Furthermore, the proposed biosynthesis and catabolism pathways of laminarin, functions of key genes, and diel regulation of laminarin were also depicted and comprehensively discussed for the first time. However, the complete pathways, functions of genes, and diel regulatory mechanisms of laminarin require more biomolecular studies. This review provides more useful information and identifies the knowledge gap regarding the future studies of laminarin and its applications.
Third-generation biofuel produced from microalgae is a viable solution to global energy insecurity and climate change. Despite an annual current global algal biomass production of 38 million litres, commercialization confronts significant economic challenges. However, cost minimization strategies, particularly for microalgae cultivation, have largely been excluded from recent studies. Therefore, this review provides essential insights into the technologies and economics of cost minimization strategies for large-scale applications. Cultivation of microalgae through aquafarming, in wastewater, or for biogas upgrading, and co-production of value-added products (VAPs) such as photo-bioreactors, protein, astaxanthin, and exopolysaccharides can drastically reduce biodiesel production costs. For instance, the co-production of photo-bioreactors and astaxanthin can reduce the cost of biodiesel production from 0.54 per litre. Though many technical challenges need to be addressed, the economic analysis reveals that incorporating such cost-effective strategies can make the biorefinery concept feasible and profitable. The cost of producing microalgal biodiesel can be lowered to 0.54L-1 when co-produced with VAPs. Most importantly, access to co-product markets with higher VAPs needs to be encouraged as the global market for microalgae-based VAPs is estimated to rise to $53.43 billion in 2026. Therefore, policies that incentivize research and development, as well as the production and consumption of microalgae-based biodiesel, are important to reduce the large gap in production cost that persists between biodiesel and petroleum diesel.
Seaweed oligosaccharides have attracted attention in food, agricultural, and medical applications recently. Compared to red and brown seaweeds, fewer studies have focused on the biological activity of green seaweed’s oligosaccharides. This study aimed to produce bioactive ulvan oligosaccharides via enzymatic hydrolysis from green seaweed Ulva lactuca. Ulvan, a water-soluble polysaccharide, was obtained by hot water extraction. Two isolated marine bacteria, Pseudomonas vesicularis MA103 and Aeromonas salmonicida MAEF108, were used to produce multiple hydrolases, such as ulvanolytic enzymes, amylase, cellulase, and xylanase, to degrade the ulvan extract. An ultrafiltration system was used to separate the enzymatic hydrolysate to acquire the ulvan oligosaccharides (UOS). The characteristics of the ulvan extract and the UOS were determined by yield, reducing sugar, uronic acid, sulfate group, and total phenols. The FT-IR spectrum indicated that the ulvan extract and the UOS presented the bands associated with O-H, C=O, C-O, and S=O stretching. Angiotensin I converting enzyme (ACE) inhibition and antioxidant activities in vitro were evaluated in the ulvan extract and the UOS. These results provide a practical approach to producing bioactive UOS by microbial enzymatic hydrolysis that can benefit the development of seaweed-based products at the industrial scale.
Algal polysaccharides, harnessed for their catalytic potential, embody a compelling narrative in sustainable chemistry. This review explores the complex domains of algal carbohydrate-based catalysis, revealing its diverse trajectory. Starting with algal polysaccharide synthesis and characterization methods as catalysts, the investigation includes sophisticated techniques like NMR spectroscopy that provide deep insights into the structural variety of these materials. Algal polysaccharides undergo various preparation and modification techniques to enhance their catalytic activity such as immobilization. Homogeneous catalysis, revealing its significance in practical applications like crafting organic compounds and facilitating chemical transformations. Recent studies showcase how algal-derived catalysts prove to be remarkably versatile, showcasing their ability to customise reactions for specific substances. Heterogeneous catalysis, it highlights the significance of immobilization techniques, playing a central role in ensuring stability and the ability to reuse catalysts. The practical applications of heterogeneous algal catalysts in converting biomass and breaking down contaminants, supported by real-life case studies, emphasize their effectiveness. In sustainable chemistry, algal polysaccharides emerge as compelling catalysts, offering a unique intersection of eco-friendliness, structural diversity, and versatile catalytic properties. Tackling challenges such as dealing with complex structural variations, ensuring the stability of the catalyst, and addressing economic considerations calls for out-of-the-box and inventive solutions. Embracing the circular economy mindset not only assures sustainable catalyst design but also promotes efficient recycling practices. The use of algal carbohydrates in catalysis stands out as a source of optimism, paving the way for a future where chemistry aligns seamlessly with nature, guiding us toward a sustainable, eco-friendly, and thriving tomorrow. This review encapsulates—structural insights, catalytic applications, challenges, and future perspectives—invoking a call for collective commitment to catalyze a sustainable scientific revolution.
The basic region/leucine zipper motif (bZIP) transcription factor (TF) family is one of the most important gene families in plants, regulating the plant growth, development, reproduction, as well as stress responses. It was well known that some bZIP TFs in higher plants can regulate polysaccharide metabolism. However, bZIP TFs in microalgae and their function on the polysaccharide metabolism are still unknown. In this study, bioinformatic and molecular methods were carried out to analyze bZIP TFs in the diatom Phaeodactylum tricornutum (Pt). As a result, a total of twenty-two PtbZIP genes were identified and subsequently classified into seven distinct clades based on phylogenetic relationships, conserved motifs, and gene structures. The number of introns varied from zero to three among the PtbZIP genes. All PtbZIP genes were randomly distributed to 16 chromosomes, and each containing one or two PtbZIP domains. Among the 22 identified PtbZIP genes, PtbZIP12 and PtbZIP13 genes were identified as a putative pair of duplicated genes. Furthermore, it was observed that laminarin content increased during the day and decreased during the night. It was proposed that the 12 PtbZIPs showing the same circadian rhythms could positively affect the accumulation of laminarin, while the 10 PtbZIP genes with the opposite expression pattern might have a negative effect on the laminarin metabolism. Based on these findings, a regulatory mechanism for laminarin biosynthesis was proposed in P. tricornutum. The results of this study provide valuable information for further analysis of bZIP TFs functions and laminarin metabolism in microalgae, which may be useful for optimizing the mass production of laminarin.
Hepatocellular carcinoma (HCC) is an aggressive tumor triggered by various factors such as virus infection and alcohol abuse. Glucuronomannan polysaccharide (Gx) is a subtype of fucoidans that possesses many bioactivities, but its anti-tumor activities in HCC have not been reported. In this paper, the anti-tumor effects of glucuronomannan oligosaccharides (Gx) and its sulfated derivatives (GxSy) on hepatocarcinoma Huh7.5 cells were investigated. The anti-proliferation, anti-metastasis activities, and underlying mechanism of Gx and GxSy on Huh7.5 cells were analyzed and compared by MTT, wound healing, transwell, and western blotting assays, respectively. Results showed that the best anti-proliferation effects were G4S1 and G4S2 among 13 drugs, which were 38.67% and 30.14%, respectively. The cell migration rates were significantly inhibited by G2S1, G4S2, G6S2, and unsulfated Gn. In addition, cell invasion effects treated with G4S1, G4S2, and G6S1 decreased to 48.62%, 36.26%, and 42.86%, respectively. Furthermore, sulfated G4 regulated the expression of (p-) FAK and MAPK pathway, and sulfated G6 down-regulated the MAPK signaling pathway while activating the PI3K/AKT pathway. On the contrary, sulfated G2 and unsulfated Gx had no inhibited effects on the FAK-mTOR pathway. These results indicated that sulfated Gx derivatives have better anti-tumor activities than unsulfated Gx in cell proliferation and metastasis process in vitro, and those properties depend on the sulfation group levels. Moreover, degrees of polymerization of Gx also played a vital role in mechanisms and bioactivities. This finding shows the structure-activity relationship for developing and applying the marine oligosaccharide candidates.
Ulvans are water-soluble sulfated polysaccharides predominantly found in the cell wall of green algae. They hold unique characteristics that are attributed to their 3D conformation, functional groups along with the presence of saccharides and sulfate ions. Traditionally, ulvans are widely used as food supplements and probiotics owing to the high content of carbohydrates. Despite their widespread usage in food industry, an in-depth understanding is required for extrapolating their potential application as a nutraceutical and medicinal agent which could be beneficial in promoting human health and well-being. This review emphasizes novel therapeutic avenues where ulvan polysaccharides can be used beyond their nutritional applications. A collection of literature points towards multifarious applications of ulvan in various biomedical fields. Structural aspects along with extraction and purification methods have been discussed. The underlying molecular mechanisms associated with its biomedical potential in different therapeutic fields like oncology, infectious diseases, inflammation, neuroprotection and tissue engineering, etc. have been unravelled. Challenges associated with clinical translation and future perspectives have been deliberated.
Atherosclerosis is characterized by the accumulation of lipid-laden cells in the arterial walls, resulting from dysregulation of cholesterol homeostasis in the macrophage, triggered by oxidized low-density lipoprotein (oxLDL). Previous studies have shown that fucoidan, a sulfated polysaccharide from brown seaweeds, has several atheroprotective activities, however, the mechanism of fucoidan protection is not fully understood. Thus, we investigated the effect of fucoidan on atherogenesis in apolipoprotein E-deficient (ApoE-/-) mice, on oxLDL uptake by macrophages, and on the expression of the flux-associated scavenger receptors by macrophages. Also, we examined the absorption and biodistribution of orally administered fucoidan. ApoE-/- mice fed on a cholesterol-rich diet supplemented with 1% fucoidan showed reduced dyslipidemia and atherosclerosis. Fucoidan was detected in blood and peripheral tissue after gavage, suggesting that it can exert direct systemic effects. In vitro, fucoidan reduced macrophage oxLDL uptake, which resulted in lower foam cell formation. This effect was associated with downregulation of the cholesterol influx-associated scavenger receptor (SR)-A expression, and upregulation of the cholesterol efflux-associated SR-B1 expression. In conclusion, fucoidan prevented oxLDL-mediated foam cell formation in macrophages by downregulating SR-A1/2 and by up-regulating SR-B1.
In this review, we summarize the current state of knowledge on the biosynthesis of carrageenan by exploring both the enzyme activities and their localizations. Genomic data, with the sequencing of the genome of Chondrus crispus and the first transcriptomic study into the life cycle stages of this organism, as well as fine carbohydrate structural determination of matrix glycans, provide leads in the study of carrageenan anabolism. Comparison to related carbohydrate-active enzymes, detailed phylogenies alongside classic histochemical studies and radioactivity assays, help predict the localization of the carrageenan-related enzyme biochemistries. Using these insights, we provide an updated model of carrageenan biosynthesis which contributes to understanding the ancestral pathway of sulfated polysaccharide biosynthesis in eukaryotes.
Fucoidans isolated from brown seaweeds are potential ingredients in the cosmetic industry. In our preosvious study, a fucoidan was isolated from the brown seaweed Turbinnaria ornata (TO-F10) and the anti-inflammatory effect of TO-F10 was evaluated. In order to further explore the potential of TO-F10 in cosmetics, in the present study, antioxidant and photoprotective effects of TO-F10 were investigated. TO-F10 remarkably protected Vero cells against AAPH-stimulated cell death by reducing apoptosis via scavenging intracellular reactive oxygen species (ROS). In addition, TO-F10 increased the survival rate of AAPH-treated zebrafish by suppressing oxidative stress displayed in reducing the levels of ROS, cell death, and lipid peroxidation. Furthermore, TO-F10 effectively attenuated UVB-induced in vitro and in vivo photodamage. TO-F10 increased the viability of UVB-irradiated human keratinocytes via suppressing apoptosis by reducing the intracellular ROS level. Besides, TO-F10 effectively attenuated in vivo photodamage stimulated by UVB irradiation via inhibiting oxidative stress and inflammatory response in zebrafish. These results demonstrate that TO-F10 possesses in vitro and in vivo antioxidant and photoprotective effects, and suggest TO-F10 is a potential ingredient in the cosmetic industry.
Obesity-induced lipid metabolism disorders are risk factors for hyperlipidemia, atherosclerosis, and non-alcoholic fatty liver disease. Seaweed oligosaccharides and Zn supplements are potential alternatives to alleviate obesity. Herein, ulvan oligosaccharide (UO) was used as a ligand to prepare a novel Zn supplement (UO-Zn). Subsequently, we explored potential mechanisms underlying UO- and UO-Zn-mediated improvements in lipid metabolism in mice fed a high-fat diet. We found that UO enhanced the abundance of key species (Blautia and Turicibacter) and functions (glycolytic, pentose phosphate, and histidine/lysine biosynthesis pathways) in the gut microbiota, thereby increasing the production of short-chain fatty acids and activating AMPK. Accordingly, UO treatment regulated the transcription of lipid metabolism genes, including ACOX1, ACC, and FASN, thereby reducing blood lipid levels and hepatic lipid accumulation. Zn could act synergistically with UO, enhancing the reversal of cholesterol transport and fatty acid β-oxidation via the MTF1/PPARα pathway, markedly reducing body and adipose tissue weights.
Diabetic wound healing encounters significant challenges due to the extreme oxidative stress resulting from excessive inflammation and microbial infections, disrupting the typical cascade of wound healing and thwarting the re-epithelialization of skin tissues. Benefiting from the biological activities of carboxymethyl cellulose (CMC) and sericin, we thus fabricated multifunctional hydrogels of CMC-Sericin. The hydrogel revealed high swelling performance alongside its porous structure. The incorporation of sericin bestowed the CMC-Sericin hydrogels with a prominent capacity to scavenge free radicals and antibacterial activity. In vivo investigations using diabetic full-thickness excision wounds demonstrated the capability of CMC-Sericin dressing to enhance diabetic wounds in rats treated or untreated with insulin concurrently. Furthermore, histopathological examinations manifested the skin tissue regeneration evidenced by the development of skin appendages like hair follicles and collagen deposition after treatment with CMC-Sericin hydrogel. Moreover, the levels of antioxidant parameters, including GSH and SOD, were substantially augmented and associated with a significant diminution in lipid peroxidation, implying a decrease in oxidative stress in the tissues. Beyond that, CMC-Sericin dressing downregulated the pro-inflammatory markers and upregulated the heat shock proteins, indicating the restoration of physiological features in cells. Strikingly, CMC-Sericin dressing remarkably promoted the healing of diabetic wounds without insulin treatment.
Microalgae are microscopic algae in sizes ranging from a few micrometers to several hundred micrometers. On average, half of the oxygen in the atmosphere is produced by the photosynthetic process of microalgae, so the role of these microorganisms in the life cycle of the planet is very significant. Pharmaceutical products derived from microalgae and commercial developments of a variety of supplements extracted from them originate from a variety of their specific secondary metabolites. Many of these microalgae are a reservoir of unique biological compounds including carotenoids, antioxidants, fatty acids, polysaccharides, enzymes, polymers, peptides, pigments, toxins and sterols with antimicrobial, antiviral, antifungal, antiparasitic, anticoagulant, and anticancer properties. The present work begins with an introduction of the importance of microalgae in renewable fuels and biodiesel production, the development of healthy food industry, and the creation of optimal conditions for efficient biomass yield. This paper provides the latest research related to microalgae-derived substances in the field of improving drug delivery, immunomodulatory, and anticancer attributes. Also, the latest advances in algal biocompounds to combat the COVID-19 pandemic are presented. In the subject of cultivation and growth of microalgae, the characteristics of different types of photobioreactors, especially their latest forms, are fully discussed along with their advantages and obstacles. Finally, the potential of microalgae biomass in biotechnological applications, biofuel production, as well as various biomass harvesting methods are described.
Chrysolaminarin is the major form of storage polysaccharides in the diatom Phaeodactylum tricornutum, which is mainly composed of β-1,3-glucan with β-1,6-branched chains (molecular weight at 10 kDa). Chrysolaminain has various biological activities such as antioxidant, anti-tumor and immune enhancement. 1,6-β-transglycosylase is speculated to be the last step in the synthesis of chrysolaminain by adding β-1,6-branched chains to the main chain of β-1,3-glucan. In this study, the putative 1,6-β-transglycosylases (PtTGS1) in P. tricornutum was characterized. PtTGS1 was overexpressed and significantly promoted the chrysolaminain synthesis and reduced lipid synthesis. The continuous accumulation of chrysolaminain was achieved by influencing the shunt of carbon metabolism without affecting the normal physiological state (growth and photosynthesis) of algal cells. These results indicated the important role of PtTGS1 gene in chrysolaminain synthesis and carbon shunt pathways.
Due to the constant increase of energy demand, new ecological sources of energy are being sought. One of the promising directions is the use of algae biomass from special cultivation or biomass floating on the sea. In order to determine the potential of algae for thermal decomposition, the pyrolysis study in thermobalance coupled with mass spectrometer was carried out at heating rates of 5, 10, 20 °C/min, in the temperature range of 30–900 °C Three types of algae: macroalgae Cladophora glomerata and Fucus vesiculosus, and microalgae Chlorella pyrenoidesa were used in this research. During the deconvolution of the derivative of the thermogravimetric curves, three peaks were assigned to the decomposition of carbohydrates, proteins and lipids. The isoconversional kinetic model used indicated that the pyrolysis process occurred in several reactions. The proposed kinetic model consists of three nth order independent parallel reactions of pseudo-components. The calculated activation energy ranged from 39 to 266 kJ/mol for carbohydrates, 177–181 kJ/mol for proteins, and 110–229 kJ/mol for lipids. The obtained results could be used in the design of 3rd generation biorefineries.
A green strategy of using citric acid as both an extractant and a cross-linking agent to expel and esterify ulvan – a marine polysaccharide from foliose Ulva sp. and filamentous Ulva sp. for hydrogel preparation was developed. Ulva sp. biomass of two different morphologies, foliose and filamentous Ulva sp., was collected from the Spiddal coast of Ireland to extract ulvan using a novel citric acid method which compared with conventional hydrochloric acid or water-based extraction methods. Extraction process parameters, viz. Ulva sp. load, extraction time, extraction temperature, and citric acid concentration, were optimised using the Taguchi experimental design. The optimised process parameters were 3 wt%, 4 h, 90 °C, and 1 wt%, respectively, for foliose and filamentous Ulva sp. At the optimised conditions, a maximum of 0.41 (±0.02) g/g and 0.39 (±0.04) g/g of ulvan yield with a protein content of 0.010 (±0.003) g/g and 0.007 (±0.002) g/g (dry weight basis) were obtained, respectively. This ulvan yield by citric acid-based extraction was superior in comparison with conventional hydrochloric acid (0.29 g/g) and water (<0.1 g/g) based extraction. Extracted ulvan was characterised and compared with commercial ulvan using proton - Nuclear Magnetic Resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and differential scanning spectroscopy (DSC) analysis. Extracted ulvan was cross-linked with 2 wt% of citric acid to form hydrogel, and the cross-linking mechanism was found to be an esterification reaction using FTIR spectroscopy. Hybridization of ulvan with varying proportions of sodium carboxymethyl cellulose (Na-CMC) was carried out to uncover the broad applications of the hydrogel in health care, agriculture, and environmental fields.
Microalgae contribute significantly to the global carbon cycle through photosynthesis. Given their ability to efficiently convert solar energy and atmospheric carbon dioxide into chemical compounds, such as carbohydrates, and generate oxygen during the process, microalgae represent an excellent and feasible carbohydrate bioresource. Microalgae-based biofuels are technically viable and, delineate a green and innovative field of opportunity for bioenergy exploitation. Microalgal polysaccharides are one of the most versatile groups for biotechnological applications and its content can be increased by manipulating cultivation conditions. Microalgal carbohydrates can be used to produce a variety of biofuels, including bioethanol, biobutanol, biomethane, and biohydrogen. This review provides an overview of microalgal carbohydrates, focusing on their use as feedstock for biofuel production, highlighting the carbohydrate metabolism and approaches for their enhancement. Moreover, biofuels produced from microalgal carbohydrate are showed, in addition to a new bibliometric study of current literature on microalgal carbohydrates and their use.