Search Results (75)

Fucoxanthin is a high-value marine xanthophyll with a unique epoxy-allene structure, predominantly produced by brown macroalgae and marine diatoms, and additionally reported in other heterokont lineages including chrysophytes and certain haptophytes. As a core light-harvesting pigment, it exhibits multiple bioactivities including lipid-lowering, antioxidant, and anti-inflammatory effects, with broad applications in functional foods, dietary supplements, and pharmaceuticals. Currently, over 70% of commercial fucoxanthin is extracted from brown macroalgae such as Saccharina japonica and Undaria pinnatifida. However, due to low endogenous pigment content and significant extraction losses, the industrial yield is only 0.05–0.1% of dry weight, failing to meet the growing downstream demand for stable high-purity supply. Marine diatoms, characterized by short growth cycles, high pigment content, and controllable culture conditions, have emerged as a core direction for industrial upgrading. Among them, Phaeodactylum tricornutum and Odontella aurita are the two most systematically studied high-yield strains with outstanding potential. This review adopts volumetric productivity (mg/(L·d)) as the core evaluation metric, which integrates biomass concentration, pigment content, and production cycle, and reflects industrial efficiency more reliably than single intracellular content data. We summarize high-yield induction methods from the dimensions of nutrient regulation, light optimization, exogenous induction, and strain improvement, and systematically compare downstream processing, safety profiles, and regulatory status between the two diatoms. Furthermore, we evaluate multi-product co-production potential and scale-up performance from a techno-economic perspective. This review provides a side-by-side benchmark of these two marine diatoms, offering a data-driven reference for process development and industrial deployment of microalgae-derived fucoxanthin. Full article

Frequent marine heatwaves (MHWs) pose significant threats to and have a profound impact on the structure and functioning of marine ecosystems. The response of marine organisms to MHWs may depend on the background temperature of their habitats. Saccharina japonica is a cold-temperate species that is vulnerable to thermal stress. However, it remains unclear how habitat-related temperatures impact responses of S. japonica to MHWs. In this study, the algae were exposed to MHWs (+∆4 °C) under two background temperatures (control level, 8 °C; warmer level, 12 °C), and the growth, photosynthetic performance, and biochemical composition were measured at the end of the MHW and the recovery periods. The results showed that a warmer background temperature increased the growth and pigment contents (Chlorophyll c and fucoxanthin) of S. japonica, but decreased chlorophyll fluorescence parameters, including the effective quantum yield, relative electron transport rate, non-photochemical quenching, and photochemical quenching. The MHWs had no significant effect on growth rate, photosynthetic performance, or biochemical compositions at the background temperature of 8 °C. In contrast, MHWs reduced growth and biochemical composition contents (Chlorophyll a, Chlorophyll c, fucoxanthin and soluble protein) at a warmer level, but the negative influence was alleviated after the recovery period. Furthermore, there was a considerable increase in the total antioxidative capacity caused by MHWs under warmer conditions. Overall, the stimulation in growth demonstrated that warmer conditions (12 °C) may provide a better growth temperature for young S. japonica but also increase the risks of biomass losses and physiological damage triggered by MHWs. These findings deepen our understandings of the tolerance and resistance of S. japonica to heatwaves and provide useful information for managing and modulating the cultivation of this important commercial seaweed. Full article

With global restrictions on in-feed antibiotics, sustainable alternatives are urgently needed to combat weaning-induced intestinal dysfunction in piglets. Fucoidan, a bioactive seaweed polysaccharide, exerts beneficial effects on gut health due to its immunomodulatory and prebiotic properties, but its mechanisms in the gastrointestinal tract of piglets remain unclear. This study investigated the effects of dietary fucoidan supplementation on growth performance, intestinal morphology, gut microbiota composition, and microbial metabolites in weaned piglets. The extracted fucoidan was characterized by a sulfate content of 23.7%, a molecular weight of 29.3 kDa, and fucose as the predominant monosaccharide. A total of 48 weaned piglets were randomly divided into two groups (n = 24 per group): a control group and a 500 mg/kg fucoidan treatment group. Growth performance was evaluated throughout the experiment. On day 28, jejunal and colonic tissues were collected to assess mucosal morphology (n = 6 per group), while cecal and colonic contents were collected for analysis of the gut microbiota and bacterial metabolites. Fucoidan supplementation significantly enhanced average daily gain (ADG, p < 0.05) and feed conversion ratio (FCR, p < 0.05) and mitigated diarrhea during the trial. Notably, piglets fed fucoidan exhibited increased villus height compared to controls (p < 0.05). Fucoidan modulated the gut microbiota by increasing cecal microbial diversity (p < 0.05) and shifting bacterial composition. These modifications involved an altered Bacteroidetes/Firmicutes ratio, as well as an enrichment of Prevotellaceae, Lactobacillus, and Lachnospiraceae (p < 0.05). Consistently, metabolite profiling analysis revealed increased cecal concentrations of lactate (p < 0.05) and butyrate (p < 0.05), which were positively associated with the growth of beneficial taxa. These findings demonstrate that fucoidan alleviates weaning-induced intestinal disorders by improving intestinal morphology and modulating gut microbiota and their metabolites. This study provides a strategy for utilizing marine-derived polysaccharides as functional feed additives to enhance animal health. Full article

Fucoidan (FUC) exhibits immunomodulatory activity; however, its effects on intestinal mucosal immunity through dendritic cell (DC)-mediated regulation remain unclear. In this study, fucoidan was extracted from Saccharina japonica by hot-water extraction and characterized by chemical composition analysis, gel permeation chromatography (GPC), and Fourier-transform infrared spectroscopy (FT-IR). Bone marrow-derived DCs were used to evaluate the effects of FUC on DC maturation and immune function. An LPS-induced acute enteritis mouse model was used to assess intestinal injury, barrier function, and DC-mediated T/B cell immune responses. Structural analysis confirmed that purified FUC has the sulfated polysaccharide characteristics. FUC promoted DC maturation and enhanced antigen-presenting capacity. In LPS-induced enteritis, FUC reduced IL-1β, IL-6, and TNF-α levels and improved intestinal barrier integrity by restoring the mRNA expression of tight-junction-related genes. Mechanistically, FUC regulated the excessive activation of the TLR4/MyD88/NF-κB pathway, increased TGF-β and IFN-γ expression, modulated Th1/Th17/Treg immune balance, and promoted B cell homing and sIgA secretion. FUC regulates DC-mediated immune responses, repairs intestinal mucosal barrier function, and restores the intestinal immune microenvironment, thereby alleviating LPS-induced intestinal inflammation and maintaining intestinal homeostasis. Full article

Saccharina japonica is an economically important stenohaline brown seaweed whose growth and yield are significantly affected by frequent salinity fluctuations in coastal aquaculture areas. The differences in salt tolerance and response characteristics among developmental stages and among tissue regions of adult-stage thalli remain unclear, and the dynamic temporal patterns of responses across stages and tissues have not been systematically elucidated. In this study, we compared the physiological responses of juvenile and adult-stage thalli under varying salinity conditions and further analyzed the responses of the basal, middle, and tip regions of adult-stage thalli to define stage- and tissue-specific patterns of salt tolerance. The results indicate that low-salinity stress caused more severe injury than high-salinity stress, as reflected by sustained decreases in Fv/Fm, increased accumulation of MDA, and aggravated tissue decay with green-rot symptoms. Juvenile sporophytes exhibited higher salt tolerance than adult-stage thalli, and within the latter, tolerance differed markedly among tissue regions, with the basal region showing greater tolerance than the middle and tip regions. The basal region maintained higher photosynthetic activity, lower lipid peroxidation levels, and more stable antioxidant and osmotic regulatory responses under stress, whereas the tip region experienced early photosynthetic inactivation and irreversible damage. qRT-PCR results showed that antioxidant- and osmotic-regulation-related genes, including SjGSH, SjGST, SjPro, SjSOD, and SjPOD, were differentially expressed under salinity treatments at 24 h and 72 h, and their expression dynamics were generally consistent with the changes in physiological indicators. Overall, this study demonstrates that the response of S. japonica to salinity stress exhibits clear developmental stage-dependent differences and tissue-specific characteristics. In adult-stage thalli, the tip region may serve as a sensitive monitoring region for low-salinity damage, the middle region may serve as a transitional region for evaluating the progression of stress-induced damage, and the basal region may be an important region for maintaining thallus growth and physiological homeostasis. This study also provides experimental evidence for low-salinity stress risk assessment, the management of key growth stages, the monitoring of sensitive tissues, and the evaluation of salt tolerance traits during S. japonica aquaculture. Full article

Attention deficit hyperactivity disorder (ADHD), a prevalent neurodevelopmental disorder characterized by inattention, impulsivity, and hyperactivity, is associated with monoaminergic dysfunction, neuronal damage, and gut microbiota disorders. Low molecular weight fucoidan (LMWF) is a sulfated polysaccharide extracted from Saccharina japonica (Phaeophyta), processes antioxidant, anti-inflammatory, and neuroprotective properties, suggesting its potential relevance for ADHD-related pathophysiology. This study investigated the therapeutic effects of LMWF on ADHD-like symptoms in spontaneously hypertensive rats (SHR). Behavioral tests revealed that LMWF reduced hyperactivity and anxiety-related behavior in the open field test, and improved spatial memory in the Morris water maze test. LMWF treatment significantly increased dopamine (DA), norepinephrine (NE), and 5-hydroxyindoleacetic acid (5-HIAA) levels in the prefrontal cortex (PFC). The transcript levels of tyrosine hydroxylase (Th) and synaptosome-associated protein-25 (Snap25) were upregulated, while dopamine transport (Dat) was downregulated in the PFC. TH protein expression was elevated in the striatum (STR), and neuronal integrity was preserved in the STR and cerebellum. LMWF also reshaped gut microbiota composition and enhanced microbial diversity, contributing to improved gut-brain axis homeostasis. These findings suggest that LMWF may serve as a promising dietary intervention for ADHD through neurochemical restoration and microbiota modulation. Full article

Marine natural products, including seaweeds, sponges, and marine microorganisms, have emerged as promising sources of bioactive compounds with diverse pharmacological properties. We investigated the antibacterial and antioxidant potential of ethanol extracts (30%, 60%, and 90%) from Saccharina japonica collected from two Korean coastal regions, Gijang and Wando, and evaluated their bioactive metabolites through integrated in vitro and in silico approaches. Among the extracts, the 60% ethanol fraction exhibited the highest total phenolic content and strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, indicating superior antioxidant capacity. Antibacterial assays revealed selective concentration-dependent inhibition against Staphylococcus aureus, while limited effects were observed against Escherichia coli. Kinetic analysis further demonstrated growth suppression of S. aureus at higher concentrations. Molecular docking was performed against multiple bacterial proteins, including DNA gyrase, topoisomerase IV, and tyrosyl-tRNA synthetase. Sterol compounds, particularly fucosterol and 24-methylene cholesterol, showed strong binding affinities across key targets, suggesting their potential role as multitarget antibacterial agents. ADMET predictions indicated favorable pharmacokinetic properties, although high lipophilicity and potential hERG II inhibition were noted. Overall, while the antibacterial effects observed were moderate, these findings suggest that marine-derived sterols from S. japonica may represent compounds of interest for further mechanistic investigation and optimization in complementary antibacterial strategies. Full article

To address the increasing global demand for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), novel and sustainable sources are required. Seaweeds have been identified as promising alternative sources of these fatty acids (FAs). This study evaluated the FA profiles of dry, commercially available seaweeds in the United Kingdom, including Porphyra spp., Palmaria palmata, Himanthalia elongata, Laminaria digitata, Saccharina japonica, Undaria pinnatifida, Sargassum fusiforme and Fucus vesiculosus. FA identification was performed by gas chromatography. The highest content of polyunsaturated FAs (PUFAs) was observed in U. pinnatifida, accounting for 67.68% of the total FAs (TFAs). EPA represented 33.34% of TFA content in Rhodophyta and 7.13% in Ochrophyta. EPA was the dominant FA in Porphyra spp., comprising 38.91% of TFAs (1064.40 mg/100 g dry weight). A higher content of EPA was also found in P. palmata (32.18%), L. digitata (13.76%), and U. pinnatifida (13.00%). DHA content was consistently lower than that of EPA, with the highest proportion observed in P. palmata (0.27% of TFAs). U. pinnatifida, P. palmata and Porphyra spp. appear to be the most promising seaweed species for providing n-3 long-chain PUFAs in human diets. Full article

Heat shock transcription factors (HSFs) play a crucial role in mediating responses to abiotic stresses. However, characterization of HSFs in macroalgae remains largely unexplored. In this study, a comprehensive analysis of HSFs was carried out in Saccharina japonica. A total of sixteen SjHSFs were identified. Phylogenetic analysis revealed that HSFs from brown algae form a distinct clade, separate from those from red algae, green algae, moss, and Arabidopsis thaliana. The DNA-binding domain was found to be highly conserved among SjHSFs. Analysis of cis-acting elements in SjHSF promoters suggested their potential roles in regulating growth, development, and stress responses. Tissue-specific expression profiles revealed differential expression of SjHSFs across various tissues of S. japonica. Under abiotic stresses, certain SjHSFs exhibited dynamic expression patterns, with particularly pronounced changes observed under high-temperature stress. We further employed a transcription factor-centered yeast one-hybrid (TF-Centered Y1H) to determine the motifs recognized by SjHSF-03. Seven conserved motifs were identified, and the distributions of these motifs were screened in the promoter regions of S. japonica genes involved in diverse biological processes and pathways. Notably, 23 heat shock protein (HSP) genes were among these motif-containing genes, and 21 out of these 23 SjHSPs were up-regulated under heat stress. Our results provide a solid foundation for future research on the specific functions of HSFs under different stress conditions and the regulatory mechanisms of HSF-mediated stress responses in S. japonica and other brown algae. Full article

Two marine bacteria, designated strains 4Alg 33^Tand 3Alg 14/1, were isolated from brown (Saccharina japonica) and green (Ulva fenestrata) macroalgae, respectively. These isolates were aerobic Gram-negative rods exhibiting a gliding motility. The 16S rRNA gene phylogenetic analysis clearly showed their belonging to the genus Formosa, the family Flavobacteriaceae, and the phylum Bacteroidota. The closest relatives of the new strains were Formosa undariae KCTC 32328^T (99.05%), Formosa arctica IMCC 9485^T (99.05%) and Formosa agariphila KMM 3901^T (98.96%). The ANI and dDDH values between the two new strains were 97.9% and 85.3%, respectively. The AAI values between 4Alg 33^T and Formosa type strains ranged from 80.1% (Formosa haliotis MA1^T) to 91.4% (F. undariae KCTC 32328^T). The cellular fatty acid and polar lipid profiles of the new isolates were generally similar to those of the type strains of Formosa species. The genomes of 4Alg 33^T and 3Alg 14/1 are represented by a circular chromosome of 4,157,724 bp and 4,316,096 bp in size with 3536 and 3879 protein-coding genes, respectively. They shared a DNA G+C content of 34.3 mol% and comprised four rrn operons. The pangenome of the genus Formosa belongs to the open type and is characterized by an abundance of CAZymes. The proportion of CAZyme genes in novel genomes was more than 5%, with a prevalence of glycoside hydrolase genes, suggesting great potential for utilizing marine-derived polysaccharides. Based on the results of polyphasic characterization, the two algal isolates represent a distinct species lineage within the genus Formosa, for which we propose the name Formosa bonchosmolovskayae sp. nov. with the type strain 4Alg 33^T (= KMM 3963^T = KCTC 72008^T). In addition, we have proposed to transfer Formosa maritima Cao et al. 2020 and Bizionia arctica Li et al. 2015 to the genus Xanthomarina Vaidya et al. 2015 as Xanthomarina maritima comb. nov. and Xanthomarina arctica comb. nov. based on a combination of the genomic and phenotypic characteristics. Full article

As a major export crop in China, Saccharina japonica cultivation suffers from significant economic losses due to disease outbreaks, with pathogen identification remaining a critical bottleneck for mariculture. In this study, a dominant bacterial strain, LJ53, was isolated from the diseased farmed S. japonica. Artificial challenge assay confirmed that this strain is the direct causative agent of bleaching symptoms on sporophytes. Based on morphological characteristics and 16S rRNA gene-based phylogeny, it was identified as Pseudoalteromonas agarivorans LJ53. Ultrastructural observation revealed that this strain destroyed host cells and caused typical pathological changes such as chloroplast disintegration. Interestingly, metagenomic analysis showed no significant difference in the relative abundance of this pathogen between healthy and diseased S. japonica tissues. However, the co-occurrence network of the disease community exhibited increased connectivity, altered modularity, and features characteristic of microbial dysbiosis. This dysbiosis disrupts the water ecological balance by destabilizing microbial symbiosis and nutrient cycling, which are essential for overall ecosystem resilience. As a result, these imbalances can exacerbate disease transmission and weaken the self-regulating capacity of marine environment, highlighting the need for integrated management strategies to restore equilibrium. These findings provide a theoretical basis for elucidating the mechanisms of bacterial diseases in S. japonica and developing future control strategies. Full article

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) that can lead to intestinal complications and systemic risks, significantly increasing the likelihood of colorectal cancer in individuals with long-term illness. Fucoidan has shown potential in alleviating UC; however, the structure–activity relationship remains challenging. The present study aims to compare fucoidan (CF) and its degraded derivatives (DF) in the prevention and treatment of UC. Structural analysis demonstrated that CF and DF possess similar monosaccharide compositions and sulfation content; however, they differ significantly in molecular weight, with CF measuring 582 kDa and DF 2.3 kDa. Additionally, DF display a lower degree of branching compared to CF. Results from the mouse model demonstrated that both CF and DF can effectively alleviate clinical symptoms of UC; however, the underlying mechanisms of action are likely to differ. Both CF and DF produced comparable improvements in the disease activity index. CF demonstrated superior efficacy in alleviating weight loss and maintaining colon length, whereas DF showed greater benefits in protecting the colonic mucosa and reducing inflammatory infiltration. The gut microbiota analysis indicated that DF was more effective in restoring microbial diversity in UC mice. Both CF and DF were capable of modulating microbial imbalances at the phylum and genus levels, although the specific taxa exhibited differences. Full article

Background/Objectives: Seaweeds have recently gained global attention as sustainable and health-promoting food sources. However, seaweeds contain iodine. While iodine is a beneficial micronutrient, its excessive intake can pose health risks. Therefore, ensuring iodine safety has emerged as a critical priority. The present study aims to determine the total iodine content in five major edible seaweeds, namely laver (Porphyra spp.), sea mustard (Undaria pinnatifida), sea tangle (Saccharina japonica), green laver (Enteromorpha spp.), and hijiki (Hizikia fusiforme), collected from 12 coastal regions in South Korea during 2020–2024. Methods: A total of 348 samples were analyzed using inductively coupled plasma mass spectrometry following microwave-assisted digestion. A risk assessment was performed based on the estimated daily intake and hazard index (HI) using both the Korean Ministry of Food and Drug Safety (MFDS), EFSA (European Food Safety Authority), and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) reference values. Results: The iodine content varied widely among the different species, with sea tangles exhibiting the highest levels (mean 2432 mg/kg dry weight). The HI values were all below 1.0, based on MFDS standards, indicating a low potential health risk. However, sea tangle exhibited values exceeding 1.0 based on the EFSA and JECFA standards. Conclusions: These findings highlight the need for species-specific iodine intake guidelines and safety regulations to ensure consumer protection and facilitate global seaweed trade. The present study provides a scientific basis for balancing the nutritional benefits of seaweed with the potential risks of overconsumption, contributing to the development of national dietary guidelines and providing evidence-based data for navigating international regulatory landscapes. Full article

This study aims to clarify the dose–response relationship between dietary β-carotene levels and gonadal pigment deposition and regulation mechanisms related to the carotenoid synthesis of Strongylocentrotus intermedius based on a 60-day feeding trial and subsequent transcriptome analysis. Adult sea urchins (initial weight: 9.33 ± 0.21 g) of three cages were given one of the dry feeds with different doses of β-carotene (0 mg/kg, 150 mg/kg, 300 mg/kg) or fresh kelp (Saccharina japonica). The results indicated that the weight gain rate (WGR) of sea urchins increased with the addition of β-carotene, with that of the C300 group being markedly higher than that of the C0 group. The addition of β-carotene significantly improved the redness (a*) and yellowness (b*) values of the gonads, with sea urchins in the C300 group exhibiting closest gonad coloration to those in the kelp-fed group. Meanwhile, β-carotene and echinenone in the gonads of the C300 group showed the highest contents, reaching 1.96 μg/kg and 11.97 μg/kg, respectively. Several differential genes, enriched in the pathways of steroid biosynthesis, oxidative phosphorylation, and ubiquitination, were screened based on transcriptome analysis. Real-time PCR further demonstrated that β-carotene significantly upregulated the expression of cholesterol 25-hydroxylase (CH25H), NADH dehydrogenase subunit 1 (ND1), NADH dehydrogenase subunit 2 (ND2), and NADH dehydrogenase subunit 4 (ND4) while it downregulated the expression of 24-dehydrocholesterol reductase (DHCR24). These results showed that 300 mg/kg β-carotene significantly increased the WGR, redness, and yellowness values, as well as the contents of β-carotene and echinenone in the gonads of S. intermedius. On the one hand, dietary β-carotene increased NADH enzyme activity, which participates in echinenone synthesis by donating electrons for the transformation of β-carotene to echinenone synthesis. On the other hand, the addition of β-carotene inhibited cholesterol synthesis by increasing the expression of CH25H and decreasing the expression of DHCR24, which could in turn increase the fluidity and permeability of the cell membranes and the transport efficiency of β-carotene and echinenone from the digestive tract to the gonads. These results provided fundamental insights into the production of sea urchin gonads with market-favored colors. Full article

Saccharina japonica (S. japonica) is a large-scale intertidal aquatic plant that exhibits characteristics such as rhizoid, holdfast, and blade differentiation. It demonstrates remarkable environmental adaptability. However, compared with higher plants, details about its phytohormone content, distribution, synthesis, and accumulation remain poorly understood. In this study, the phytohormone contents distribution and expression patterns of synthetic genes in different parts of S. japonica, including the rhizoid, petiole, basis, middle, and tip, were analyzed in detail by combining targeted metabolomics and transcriptomics analyses. A total of 20 phytohormones were detected in S. japonica, including auxin, abscisic acid (ABA), cytokinin (CTK), ethylene (ETH), gibberellin (GA), jasmonate acid (JA), and salicylic acid (SA), with significant site-differentiated accumulation. ABA and JA were significantly enriched in the tips (28.01 ng·g⁻¹ FW and 170.67 ng·g⁻¹ FW, respectively), whereas SA accumulated specifically only in the rhizoid. We also identified 12 phytohormones, such as gibberellin A1, methyl jasmonate, and trans-zeatin for the first time in S. japonica. Transcriptomic profiling revealed the tissue-specific expression of phytohormone biosynthesis genes, such as CYP735A (CTK synthesis), in the rhizoids and LOX/NCED (JA/ABA synthesis) in the tips. Key pathways, such as carotenoid biosynthesis and cysteine methionine metabolism, were found to be differentially enriched across tissues, aligning with hormone accumulation patterns. Additionally, an enrichment analysis of differentially expressed genes between various parts indicated that different parts of S. japonica performed distinct functions even though it does not have organ differentiation. This study is the first to uncover the distribution characteristics of phytohormones and their synthetic differences in different parts of S. japonica and elucidates how S. japonica achieves functional specialization through non-specific phytohormone regulation despite lacking organ differentiation, which provides an important theoretical basis for research on the developmental biology of macroalgae and their mechanisms of response to adversity. Full article