Laminaria Japonica Research Articles

Novel insights into the rhizosphere and seawater microbiome of Zostera marina in diverse mariculture zones

BackgroundSeagrasses offer various ecosystem services and possess high levels of primary productivity. However, the development of mariculture has affected the homeostasis of seagrass meadow ecosystems. Plant-microbiome associations are essential for seagrasses health, but little is known about the role of environmental microbiomes and how they affect seagrass in a mariculture environment. In this study, we investigated the influence of mariculture on the rhizosphere and seawater microbiome surrounding Zostera marina and focused on the bacterial, eukaryotic, and fungal components in the composition, diversity, metabolism, and responses to mariculture-related environmental factors.ResultsSignificant differences in the composition, richness, diversity, and internal relations of the bacterial community between the seawater and rhizosphere sediment surrounding Z. marina were observed, while differences in the eukaryotic and fungal communities were less significant. More complex bacterial and fungal co-occurrence networks were found in the seawater and rhizosphere sediment of the Saccharina japonica (SJ) and sea cucumber (SC) culture zones. The seawater in the SJ zone had higher levels of dissimilatory and assimilatory nitrate reduction, denitrification, and nitrogen fixation processes than the other three zones. The assimilatory sulfate reduction enzymes were higher in the rhizosphere sediments of the SJ zone than in the other three zones. Tetracycline, sulfonamide, and diaminopyrimidine resistance genes were enriched in the mariculture SJ and SC zones.ConclusionsOur findings might contribute to a better understanding of the effects of mariculture on the seagrass and the meadow ecosystems and thus revealing their potential operating mechanisms. These insights may serve to raise awareness of the effects of human activities on natural ecosystems, regulation of antibiotic usage, and environmental restoration.7tqXcmUUPbCQ9vMfWLp9EQVideo

Laminaria japonica Aresch-Derived Fucoidan Ameliorates Hyperlipidemia by Upregulating LXRs and Suppressing SREBPs.

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide, and hyperlipidemia is one major inducing factor of CVD. It is worthy to note that fucoidans are reported to have hypolipidemic activity with species specificity; however, the underlying mechanisms of action are far from clarification. This study is aimed at investigating the plasma lipid-lowering mechanisms of the fucoidan from L. japonica Aresch by detecting the levels of hepatic genes that are involved in lipid metabolism. Our results demonstrated that the fucoidan F3 significantly lowered total cholesterol and triglyceride in C57BL/6J mice fed a high-fat diet. In the mouse liver, fucoidan F3 intervention significantly increased the gene expression of peroxisome proliferator-activated receptor (PPAR) α, liver X receptor (LXR) α and β, and ATP-binding cassette transporter (ABC) G1 and G8 and decreased the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9), low-density lipoprotein receptor, cholesterol 7 alpha-hydroxylase A1, and sterol regulatory element-binding protein (SREBP) 1c and SREBP-2. These results demonstrated that the antihyperlipidemic effects of fucoidan F3 are related to its activation of PPARα and LXR/ABC signaling pathways and inactivation of SREBPs. In conclusion, fucoidan F3 may be explored as a potential compound for prevention or treatment of lipid disorders.

Increased Accumulation of Ginsenosides in Panax ginseng Sprouts Cultivated with Kelp Fermentates

Currently, new agri-tech has been developed and adapted for the cultivation of crops using smart farming technologies, e.g., plant factories and hydroponics. Kelp (Laminaria japonica), which has a high industrial value, was considered as an alternative to chemicals for its eco-friendly and sustainably wide use in crop cultivation. In this study, a fermented kelp (FK) was developed for use in hydroponics. The FK contained various free and protein-bound amino acid compositions produced by fermenting the kelp with Saccharomyces cerevisiae. Supplementing FK as an aeroponic medium when cultivating ginseng sprouts (GSs) elevated the total phenolic and flavonoid contents. Additionally, seven ginsenosides (Rg1, Re, Rb1, Rc, Rg2, Rb2, and Rd) in GSs cultivated with FK in a smart-farm system were identified and quantified by a high-performance liquid chromatography-evaporative light scattering detector/mass spectrometry analysis. Administering FK significantly increased the ginsenosides in the GSs compared to the control group, which was cultivated with tap water. These results indicate the FK administration contributed to the increased accumulation of ginsenosides in the GSs. Overall, this study suggests that FK, which contains abundant nutrients for plant growth, can be used as a novel nutrient solution to enhance the ginsenoside content in GSs during hydroponic cultivation.

Biochar mitigates the mineralization of allochthonous organic matter and global warming potential of saltmarshes by influencing functional bacteria

Saltmarshes are suffering from severe degradation due to anthropogenic activities, leading to the loss of blue carbon and greenhouse gas (GHG) emissions. Given the significant potential of biochar in mitigating climate change, adding biochar to saltmarshes would alleviate this situation. This study investigated the effects of different biochar (made from Spartina alterniflora, corn straw, and Laminaria japonica) and their aged biochar on the carbon fraction contents, GHG emissions, and microbial community structure of saltmarsh soils with allochthonous organic matter (Enteromorpha prolifera) addition. After 60 days of incubation, total organic carbon (TOC) loss and global warming potential (GWP) of biochar-amended soils were reduced by 67.29–124.33% and 4.91–123.24%, respectively (p < 0.05). Biochar reduced the proportion of labile carbon (dissolved organic carbon (DOC) and microbial biomass carbon (MBC)) in organic carbon by 61.92–86.15% (p < 0.05). In addition, biochar reduced the relative abundance of specific functional bacteria (inc. cellulolysis, aromatic compound degradation, and xylanolysis) involved in organic carbon decomposition by 20.02–37.82% (p < 0.05). These results suggest that even in the presence of high levels of liable organic matter, the application of biochar to saltmarshes has a sustained effect in promoting carbon accumulation and reducing GHG emissions, and this effect is regulated by a decrease of functional bacteria associated with carbon metabolism. Therefore, the in situ study of biochar on restoring carbon sink function of saltmarshes is proposed for practical engineering in future.Graphical

Macroalgal virosphere assists with host-microbiome equilibrium regulation and affects prokaryotes in surrounding marine environments.

The microbiomes in macroalgal holobionts play vital roles in regulating macroalgal growth and ocean carbon cycling. However, the virospheres in macroalgal holobionts remain largely underexplored, representing a critical knowledge gap. Here we unveil that the holobiont of kelp (Saccharina japonica) harbors highly specific and unique epiphytic/endophytic viral species, with novelty (99.7% unknown) surpassing even extreme marine habitats (e.g. deep-sea and hadal zones), indicating that macroalgal virospheres, despite being closest to us, are among the least understood. These viruses potentially maintain microbiome equilibrium critical for kelp health via lytic-lysogenic infections and the expression of folate biosynthesis genes. In-situ kelp mesocosm cultivation and metagenomic mining revealed that kelp holobiont profoundly reshaped surrounding seawater and sediment virus-prokaryote pairings through changing surrounding environmental conditions and virus-host migrations. Some kelp epiphytic viruses could even infect sediment autochthonous bacteria after deposition. Moreover, the presence of ample viral auxiliary metabolic genes for kelp polysaccharide (e.g. laminarin) degradation underscores the underappreciated viral metabolic influence on macroalgal carbon cycling. This study provides key insights into understanding the previously overlooked ecological significance of viruses within macroalgal holobionts and the macroalgae-prokaryotes-virus tripartite relationship.

Pyrolysis of Laminaria japonica with biochar production and its characteristics

In the present paper, biochar from the Laminaria japonica from brackish lagoons (Sea of Okhotsk, Sakhalin Island) was obtained by a stepwise pyrolysis at 500 °C. The properties of concerned biochar (elemental composition, specific surface area, particle size distribution) were studied. It was shown that the Laminaria japonica biochar has 0.2–18 μm particle sizes with a complex branched surface of high microporosity and a specific surface area of 38.6 m2g-1. Aforementioned biochar has the high content of carbon (~60 at%) and high content of oxygen (~34 at.%).

A comparative study of the hypolipidemic effects and mechanisms of action of Laminaria japonica- and Ascophyllum nodosum-derived fucoidans in apolipoprotein E-deficient mice.

The structural characteristics of fucoidans exhibit species and regional diversity. Previous studies have demonstrated that Laminaria japonica- and Ascophyllum nodosum-derived fucoidans have type I and type II fucosyl chains, respectively. These chemical differences may contribute to distinct hypolipidemic effects and mechanisms of action. Chemical analysis demonstrated that the percentage contents of sulfate, glucuronic acid, and galactose were higher in L. japonica-derived fucoidans than those of A. nodosum-derived fucoidans. In hyperlipidemic apolipoprotein E-deficient mice, both A. nodosum- and L. japonica-derived fucoidans significantly decreased the plasma and hepatic levels of total cholesterol and triglyceride, leading to the reduction of atherosclerotic plaques. Western blotting experiments demonstrated that these fucoidans significantly enhanced the expression and levels of scavenger receptor B type 1, cholesterol 7 alpha-hydroxylase A1, and peroxisome proliferator-activated receptor (PPAR)-α, contributing to circulating lipoprotein clearance and fatty acid degradation, respectively. Differentially, L. japonica-derived fucoidan significantly increased the LXR/ATP-binding cassette G8 signaling pathway in the small intestine, as revealed by real-time quantitative PCR, which may lead to further cholesterol and other lipid excretion. Collectively, these data are useful for understanding the hypolipidemic mechanisms of action of seaweed-derived fucoidans, and their potential application for the prevention and/or treatment of atherosclerotic cardiovascular diseases.

Effects of high-pressure processing on the physicochemical and adsorption properties, structural characteristics, and dietary fiber content of kelp (Laminaria japonica)

To investigate the effects of high-pressure processing (HPP) on the physicochemical and adsorption properties and structural characteristics of kelp, kelp slice (KS) and kelp powder (KP) were treated under different pressures (300, 450, and 600 MPa) for 5 and 10 min. Compared to untreated KP, HPP-treated KP yielded a 1.31-fold increase in water holding capacity (600 MPa/5 min), a 0.12-fold increase in swelling capacity (450 MPa/10 min), a 1.33-fold increase in oil holding capacity (600 MPa/10 min), a 10-fold increase in glucose adsorption capacity (450 MPa/10 min), and a 0.22-fold increase in cholesterol adsorption capacity (163.1 mg/g DW at 450 MPa/10 min), and exhibited good Cd (Ⅱ) adsorption capacity when its concentration was 10 mmol/L in the small intestine. The physicochemical properties of HPP-treated KS were not improved due to its low specific surface area. In addition, HPP treatment efficiently reduced the particle size of KP and increased its total and soluble dietary fiber content by 17% and 63% at 600 MPa/10 min, respectively. Scanning electron microscope micrographs demonstrated that the surface of HPP-treated KP was rough and porous, and the specific surface area increased with increasing pressure and processing time. To conclude, the results obtained in the present study suggest that HPP is a promising processing method for improving the functionality and structural characteristics of KP and provide a theoretical basis for the utilization of HPP-treated KP as a fiber-rich ingredient in the functional food industry.

Laminaria japonica Polysaccharides Improves the Growth Performance and Faecal Digestive Enzyme Activity of Weaned Piglets.

The aim of this experiment was to investigate the effect of Laminaria japonica polysaccharide (LJP) supplementation at levels of 100, 200, or 400 mg/kg on the growth performance, faecal digestive enzyme activity, and serum biochemistry and amino acids of weaned piglets. One hundred and twenty weaned piglets (Barkshire × Licha Black, 21 days old, 6.13 ± 0.16 kg) were randomly divided into four groups with five replicates of six piglets in each group based on body weight. Piglets were fed with different levels (0, 100, 200, and 400 mg/kg) of LJP for a 21-day trial. On day 21, faecal and blood samples were collected from one piglet per pen. The results showed that the supplementation of the 200 and 400 mg/kg LJP significantly increased average daily gain (ADG) and average daily feed intake (ADFI) compared to the control group (p = 0.007; p = 0.002), and dietary LJP linearly increased ADG and ADFI (p = 0.002; p < 0.001). In addition, the supplementation of the 200 and 400 mg/kg LJP significantly increased faecal amylase activity (p < 0.001) compared to the control group, and dietary LJP linearly increased faecal amylase and lipase activities (p = 0.001; p = 0.037). Moreover, dietary LJP at 400 mg/kg increased serum histidine content compared to the other groups (p = 0.002), and dietary LJP linearly increased the contents of serum histidine and asparagine in piglets (p < 0.001; p = 0.046). In conclusion, supplementation of 200 and 400 mg/kg LJP could enhance growth performance and faecal digestive enzyme activity and modulate the serum amino acid content of weaned piglets, potentially contributing to the health of weaned piglets.

Potential application of Saccharina japonica and its extracts in cosmetology

Saccharina japonica (S. japonica), a type of brown algae widely consumed in east Asia due to its enormous health benefits, has now been greeted with great expectation in the field of cosmetics. Although many cosmetological functions of S. japonica extracts have been reported, there is still a lack of comprehensive review on the potential application of S. japonica and its extract in cosmetology. This article aims to sum up the cosmetological functions of S. japonica extracts, including anti-inflammation, skin whitening, anti-oxidation, and anti-bacterial activities. Moreover, the production of bioactive chemicals from S. japonica is explored, hoping to provide new insights into cosmetic manufacturing. Study exploration was conducted using online databases (PubMed) using the keywords Saccharina japonica, Laminaria japonica, kelp, cosmetics, anti-inflammation, skin whitening, anti-oxidation, anti-bacterial, etc., focusing on established pre-clinical trials proving relative bioactivities.

Laminaria japonica polysaccharide alleviates type 2 diabetes by regulating the microbiota-gut-liver axis: A multi-omics mechanistic analysis

The hypoglycemic effects of low-molecular-weight Laminaria japonica polysaccharide (LJO) were investigated in type 2 diabetes mellitus (T2DM) mice, focusing on its effect on the microbiome, metabolome, and transcriptome. The findings demonstrated that LJO significantly reduced fasting blood glucose levels, insulin levels, and inflammatory factors. Additionally, LJO induced changes in gut microbiota composition and increased the concentrations of cecal short-chain fatty acids. Analysis of transcriptomics and metabolomics data revealed that LJO primarily altered the endocrine and digestive systems, signal transduction, and lipid metabolism. It led to a decrease in palmitic acid levels and an increase in glutathione levels. Real-time quantitative polymerase chain reaction assay suggested that LJO upregulated Irs1 expression, consequently reducing insulin resistance. These findings strongly suggest that LJO holds promise in ameliorating T2DM and may serve as a potential dietary supplement for patients with T2DM.

Fucoidan attenuates chronic colitis and behavioral deficits by reshaping gut microbiota-brain axis balance

Inflammatory bowel disease (IBD) often coexists with depression, posing considerable challenges for treatment. This study aimed to investigate the therapeutic potential of fucoidan, a compound derived from Laminaria japonica, in a dextran sulfate sodium (DSS)-induced model of IBD with comorbid depression. The administration of fucoidan demonstrated significant therapeutic efficacy, as it reduced disease activity, increased sucrose preference, and decreased immobility time, suggesting benefits for both IBD and depression. Fucoidan had a noteworthy impact on the gut microbiota, characterized by an increase in the abundance of Firmicutes and Lactobacillus. Additionally, it strengthened the integrity of the colonic barrier by upregulating tight junction proteins (ZO-1, Occludin, and Claudin-1) and reduced colonic inflammation via the TLR4/NF-κB pathway. Fucoidan also exhibited the ability to suppress peripheral inflammation and lower stress response hormone levels, particularly corticosterone. Furthermore, fucoidan reduced the number of microglia, as well as decreasing cytokines such as interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) levels, indicating a decrease in neuroinflammation in IBD-afflicted mice. In conclusion, fucoidan effectively mitigates IBD comorbid with depression by modulating the gut microbiota-brain axis. These findings offer promise for fucoidan as a natural compound to manage both IBD and associated depressive symptoms.

Effects of ultra-fine micronization on the structure, rheological and functional properties of dietary fiber from Laminaria japonica

Laminaria japonica is known to be a rich source of dietary fiber (DF). The DF in L. japonica was extracted by combined enzymatic and chemical method in this study. The effect of ultra-fine pulverization on structural and functional properties of DF fractions were also investigated. The results displayed that the molecular weight of DF was 2.22 × 107 Da. After ultra-fine grinding, the viscosity of soluble dietary fiber (SDF) suspension increased from 4.65 ± 0.08 to 6.89 ± 0.24 mPa·s. In addition, ultra-fine grinding significantly reduced the particle size of DF with higher insoluble dietary fiber (IDF) yields. L. japonica IDF exhibited significant enhancement on absorption capacities of nitrite ion absorption, cholesterol and glucose, which could be utilized as potential ingredients in several DF intensified foods. This work could provide understanding into the influence of micronization on the structure-function relationship of food materials rich in dietary fiber.

Effects of Supplementary Kelp Feeding on the Growth, Gonad Yield, and Nutritional and Organoleptic Quality of Subadult Sea Urchin (Strongylocentrotus intermedius) with Soya Lecithin Intake History.

A 23-week feeding experiment was conducted to investigate the effects of supplementary kelp feeding on the growth, gonad development, and nutritional and sensory properties of sea urchin (Strongylocentrotus intermedius) with soya lecithin (SL) intake history. The feeding experiment was divided into experimental phase I and phase II. During phase I, 48 subadult sea urchins (initial weight: 6.28 ± 0.07 g) were fed one of the feeds with different levels of SL (0%, 1.6%, 3.2%) or kelp (Saccharina japonica) for 12 weeks. Then, all sea urchins were fed kelp for the next 11 weeks during the phase II. Each diet was randomly allocated to six cages of sea urchins. The results of phase I showed that weight gain rate (WGR), gonadosomatic index (GSI), gonad sensory properties (color and texture), and essential amino acid (EAA) contents were not significantly affected by SL level in the feed groups. High level (3.2%) of SL suppressed gonad development of S. intermedius with retarded gametogenesis in the 3.2% SL group (stage Ⅱ) compared to those fed 0% and 1.6% SL groups (stage Ⅲ). Sea urchins fed dry feeds exhibited significantly lower WGR and values of color (redness and yellowness) and texture (hardness and gumminess) but higher contents of EAA in the gonads than those fed kelp. The n-3/n-6 polyunsaturated fatty acid (PUFA) and eicosapentaenoic acid (EPA) of gonads in the groups fed with dry feeds showed no significant differences, but were significantly lower than that of kelp group. At the end of phase II, the gonad yellowness and EPA content of gonads in all dry feed groups were significantly increased by supplementary kelp feeding, with a higher increase observed in S. intermedius with SL intake history, while arachidonic acid (ARA) content was significantly improved by supplementary kelp feeding in S. intermedius with SL intake history. Gonad texture was improved to some extent by supplementary kelp feeding. These results indicated that S. intermedius fed dry feeds showed significantly higher GSI and EAA but poorer organoleptic quality and lower n-3/n-6 PUFA and EPA than those fed kelp. Kelp supplementary feeding improved the fatty acid value and organoleptic quality of gonads, especially for the sea urchins with SL intake history.

Temperature-Dependent Food Consumption Rates of the Sea Urchin Mesocentrotus nudus and Top Shell Turbo sazae: Potential Impacts on Seaweed Beds.

In Korea, the expansion of barren ground and a shift in macrograzer habitats due to increasing water temperatures associated with climate change are becoming increasingly problematic. This study assessed the potential effects of the sea urchin Mesocentrotus nudus and top shell Turbo sazae on seaweed beds by examining changes in their food consumption rates in response to changes in temperature. The food consumption rates of kelp (Saccharina japonica) for both species were estimated at 5 °C, 10 °C, 15 °C, 20 °C, and 25 °C in laboratory experiments. The rate for M. nudus increased with increasing water temperature, with the highest rate of 0.001 g g-1 d-1 at 15 °C and 20 °C, and the lowest at 25 °C, which killed some individual sea urchins. The rate for T. sazae also increased with increasing water temperature, with the highest being 0.087 g g-1 d-1 at 25 °C and the lowest being at 5 °C. T. sazae had a higher food consumption rate than M. nudus at all temperatures; as water temperature increased, the difference between species increased, with the largest difference occurring at 25 °C. These findings indicate that as water temperature increases, T. sazae places greater feeding pressure on macroalgae than M. nudus.

The Potential Hypoglycemic Competence of Low Molecular Weight Polysaccharides Obtained from Laminaria japonica.

This study aimed to assess the hypoglycemic efficacy of low molecular weight polysaccharides fractions obtained from Laminaria japonica (LJOO) in a model of type 2 diabetes mellitus (T2DM) constructed using mice. Biochemical parameters were measured after 4 weeks of continuous gavage, and fasting blood glucose (FBG) concentrations were analyzed. Pathological changes in tissues were assessed. The intestinal contents were obtained for 16S rDNA high-throughput sequencing analysis and detection of short-chain fatty acids (SCFAs). LJOO lowered FBG and insulin concentrations. It altered the gut microbiota composition, as evidenced by enriched probiotic bacteria, along with an increase in the Bacteroidetes/Firmicutes ratio and a decrease in the population of harmful bacteria. LJOO stimulated the growth of SCFA-producing bacteria, thereby increasing cecal SCFAs levels. LJOO can potentially aid in alleviating T2DM and related gut microbiota dysbiosis. LJOO may be used as a food supplement for patients with T2DM.

Grazing pressure of sea urchin Mesocentrotus nudus estimated from seawater temperature and wave height, and its effects on the early growth of annual kelp Saccharina japonica in northeastern Japan

Grazing by the sea urchin Mesocentrotus nudus plays a vital role in the development of marine forests of annual kelp, Saccharina japonica, along the Pacific coast of northeastern Japan. The grazing rate of sea urchins, which are rigorously temperature dependent, affects the chance of germination/survival of the kelp during winter/spring when seawater temperatures in this region are highly variable among years. It has previously been found that if the mean seawater temperature between February and March remained below 5.5 °C, kelp forests in this region would establish later in the year. However, the mechanism leading to this success or failure of kelp forests to develop has yet to be investigated in detail.Laboratory experiments confirmed that the grazing rate and movement of the sea urchin decreased as seawater temperature declined from 12 °C to 3 °C. Field observations, using interval cameras from autumn to spring, revealed that the density of sea urchins on artificial reefs decreased at lower seawater temperatures and/or higher significant wave heights (SWH). Using these relationships, the grazing pressure by sea urchins (= grazing rate × density) in the site was estimated based on seawater temperature and SWH. Comparing the grazing pressures among past years with different states of kelp forests, conditions needed to establish kelp forests were revealed. Extremely low grazing pressure (< 0.5 g m−2 day−1) lasted for a total of 31 days in 2015 when kelp grew densely, while this condition occurred on 11 and 14 days respectively in 2019 and 2022 when kelp was sparse. Kelp did not grow in 2016 when the grazing pressure continuously remained above 0.5 g m−2 day−1. At this study site, such combinations of seawater temperature and SWH as 4 °C and 1.0 m, 6 °C and 2.3 m, and 8 °C and 3.7 m would equate to a grazing pressure of 0.5 g m−2 day−1. To develop a dense kelp forest, grazing pressure was required to be lower than 0.5 g m−2 day−1 for about a month as in 2015. Though these figures should be adjusted, a model and scheme of this study will be applied to the other areas where kelp forest restoration/management plans are required.

Fucogalactan Sulfate (FS) from Laminaria japonica Regulates Lipid Metabolism in Diet-Induced Humanized Dyslipidemia Mice via an Intestinal FXR-FGF19-CYP7A1/CYP8B1 Pathway.

Our previous study found that fucogalactan sulfate (FS) from Laminaria japonica exhibited significant hypolipidemic effects. To further elucidate the mechanism, we first constructed a dyslipidemia mouse model with humanized gut microbiota and proved the main differential metabolic pathway involved bile acid metabolism. Then, we evaluated the beneficial effects of FS on dyslipidemia in this model mice, which revealed that oral FS administration reduced serum cholesterol levels and mitigated liver fat accumulation. Gut microbiota and microbiome analysis showed FS increased the abundance of Ruminococcaceae_NK4A214_group, GCA-900066755, and Eubacterium, which were positively associated with the fecal DCA, β-MCA, and HDCA. Further investigation demonstrated that FS inhibited the hepatic farnesoid X receptor (FXR), while activating the intestinal FXR-FGF19 pathway, leading to suppression of CYP7A1 and CYP8B1, as well as potentially reduced bile acid synthesis and lipid absorption. Overall, FS regulated lipid metabolism in diet-induced humanized dyslipidemia mice via the bile acid-mediated intestinal FXR-FGF19-CYP7A1/CYP8B1 pathway.

The isolation and functional identification of a phosphoenolpyruvate carboxykinase gene from Saccharina japonica

Similar to other macroalgae, Saccharina japonica has CO2-concentrating mechanism (CCM) that allows high photosynthesis efficiency and elevates biomass. Phosphoenolpyruvate carboxykinase (PEPCK) in cytoplasm is an essential component of CCM. However, no reports on cytosolic PEPCK of S. japonica are available. In this study, the full-length cDNA sequence of a PEPCK gene (SjPCK1) predicted to be localized in cytoplasm, was screened from the full-length transcriptome of S. japonica gametophytes and identified by RT-PCR. The complete cDNA sequence of SjPCK1 was 2174 bp in length, which encompassed an open reading frame (ORF) of 1734 bp, a 5′- untranslated region (UTR) of 216 bp and a 3′-UTR of 224 bp. In parallel, the genomic DNA of SjPCK1 was 21 294 bp in length, characterized by the presence of 11 introns and 12 exons. It encoded a protein of 577 amino acids with a molecular weight of 63 kD and an isoelectric point of 8.47. Amino acid sequence alignment showed that the functional sites of PEPCK were highly conserved in the selected species. Phylogenetic analysis and sequence characterization showed that SjPCK1 was an ATP-dependent PEPCK. SjPCK1 gene was expressed by using Escherichia coli prokaryotic expression system, and the SjPCK1 protein with His 6 tag (rSjPCK1) was 81.93 kD in molecular weight. Enzyme activity assay results showed that the specific activity of carboxylase and decarboxylase of rSjPCK1 was 1.91 ± 0.29 U/mg prog and 11.3 ± 1.97 U/mg prog, respectively. These findings provide valuable molecular and biochemical insights for a further analysis of the role of cytosolic PEPCK in the storage of inorganic carbon in S. japonica.

Influence of red yeast rice extract fermentation on fucoidan profiles, inorganic elements and flavor properties of the kelp Saccharina japonica

This study evaluated the efficacy of fermentation on Saccharina japonica (SJ). Changes of fucoidan, heavy metals, iodine and flavor profiles of fermented SJ (FSJ) were determined. Results showed that fermentation decreased the yield and molecular weight of fucoidan and increased the levels of phenolic compounds. The antioxidant activity of fucoidan also increased. It is notable that the fermentation process resulted in a significant reduction of iodine, lead, chromium and cadmium. The flavor properties of SJ during the fermentation process were evaluated. A total of 44 volatile compounds were identified which were correlated with the odor attributes of FSJ. FSJ fermented for five days (FSJ-5) showed the highest overall score for desirable aroma properties dominated by “fruity” and “sweet” odors. The results proved that fermentation is a promising methodology to improve the bioactivity, safety and flavor properties of SJ.