Seaweed Species Research Articles

Fermentation of brown seaweeds Alaria esculenta and Saccharina latissima for new product development using Lactiplantbacillus plantarum, Saccharomyces cerevisiae and kombucha SCOBY

Two seaweed species were examined (Alaria esculenta and Saccharina latissima) as a fermentation feedstock for the development of a beverage. Three microbial groups were selected for experimentation; a single-species bacterium; Lactiplantibacillus plantarum, a single-species yeast; Saccharomyces cerevisiae and a multi-species culture; kombucha SCOBY (Symbiotic Culture of Bacteria and Yeast). Results showed SCOBY cultures were more successful in fermenting A. esculenta than S. latissima due to the lowered glucose content (4.069 ± 0.174 mg / mL and 12.224 ± 2.249 mg / mL, respectively). Likewise, L. plantarum played a major role in fermenting S. latissima, over A. esculenta, resulting in a lowered pH in the former but not the latter (6.44 ± 0.040 and 4.825 ± 0.045, respectively). S. cerevisiae does not appear to have been suitable as a fermentation medium for these two seaweed species under these conditions due to the lack of pH lowering, glucose reduction and acid production. All treatments showed an increased production of lactic acid, especially the SCOBY treated samples, which is an indicator of fermentation. There is potential for optimization of the seaweed fermentation process through strain selection, fermentation conditions optimization (temperature, time, pH) and seaweed biomass pretreatment. Glutamic acid, the amino acid responsible for umami flavour, was found in greater quantities in the S. cerevisiae treated seaweed, indicating that fermentation using S. cerevisiae cultures may improve the umami flavour profile of a seaweed fermented beverage product. In order to see if the seaweed species used had an impact on the SCOBY microbial makeup, the DNA profiles of the two SCOBYs used were analyzed. There were significant differences between the two SCOBYs. The A. esculenta SCOBY showed slightly rarer species of fungi and the species abundance of fungi was greater than that of S. latissima SCOBY. Furthermore, the number of fungal operational taxonomic units (OTUs) in A. esculenta SCOBY was higher than that in S. latissima SCOBY. This study shows the potential of using brown seaweed species as a fermentation substrate to develop a novel, fermented beverage.

The distribution of radiotoxic 137Cs concentrations in seaweed and mussel species in the Mediterranean Sea

A study was conducted to determine the 137Cs activity concentrations in various seaweed and mussel samples from the North East Mediterranean Sea, including the brown algae (Dictyota dichotoma) and oarweed (Laminaria digitata), and mussel species (Haliotis asinina, Mytilus edulis and Mytilus galloprovinciali). The 137Cs activity concentration in seaweed species exhibited varying levels, ranging from 84.20 ± 1.82 to 236.05 ± 5.72 mBq kg−1 fresh weight (fw) for oarweed, and 106.29 ± 2.26 to 252.38 ± 6.04 mBq kg−1 fw for brown algae. The 137Cs value in mussel species were between 12.94 ± 0.51–101.84 ± 1.35 mBq kg−1 fw for M. galloprovincialis, 15.49 ± 0.58–71.52 ± 1.16 mBq kg−1 fw for M. edulis, and 10.36 ± 0.11–69.13 ± 1.34 mBq kg−1 fw for H. asinine. When comparing the 137Cs concentration in seaweed and mussel species, the average concentration in seaweeds was approximately four times higher than that in mussels. This significant difference in radioisotope concentration highlights the potential for higher bioaccumulation of 137Cs in seaweeds compared to mussels.

Iodine concentration and palatability of milk from cows fed the common red seaweed species Himanthalia elongata

Iodine concentration and palatability of milk from cows fed the common red seaweed species Himanthalia elongata

Species-specific arsenic species and health risk assessment in seaweeds from tropic coasts of South China Sea

Arsenic (As) is a notorious toxic contamination in marine environments, while the toxicity and health risk of As is highly dependent on As species in seafoods. In this study, we hypothesized that the species-specific As bioaccumulation and species resulted in species-specific healthy risk of As in seaweeds. To test the hypothesis, we collected 10 common edible seaweeds from the coast of Hainan Island in South China Sea. Then we comparatively quantified concentration of total As and 5 major As species [AsB, DMA, MMA, As(III), and As(V)] in seaweeds. The results revealed that the concentrations of total As varied significantly among 10 seaweed species. Specially, the highest total As concentration were found in brown seaweeds, followed by red seaweeds, and green seaweeds. Furthermore, the percentage of 5 As species to total As differed significantly among 10 seaweeds. The percentage of AsB was highest in Caulerpa lentillifera (53%) and lowest in Sargassum oligocystum (13%), while that of As(V) was lowest in Caulerpa lentillifera (21%) and highest in Sargassum oligocystum (81%). The iAs [As(III) + As(V)] exhibited highest value in brown seaweeds and least value in green seaweeds. The potential human health risk assessment indicated that the consumption of brown seaweeds of Sargassum oligocystum and Sargassum polycystum could cause a considerable carcinogenic risk and non-carcinogenic risk to residents. Overall, our findings here largely validated our hypothesis that the species-specific As bioaccumulation and As species had great significance to healthy risk of As in seaweeds.

Dietary sulfated polysaccharides extracted from Caulerpa sp. and Padina sp. modulated physiological performance, antibacterial activityand ammonia challenge test in juvenile rainbow trout (Oncorhynchus mykiss).

Nowadays, the use of seaweed derivatives in aquaculture has drawn attention for their potential as an immunostimulant and growth promotor. The sulfated polysaccharide extracted (SPE ) from green (Caulerpa sp.; SPC) and brown (Padina sp.; SPP) seaweeds with two concentrations (0.05% and 0.1%); nominated in four groups: SPC0.05 , SPC0.1 , SPP0.05 , SPP0.1 and control group (free of SPE ) were used for juvenile rainbow trout (Oncorhynchus mykiss) diet. Fish (N: 150; 8.5 ± 0.2 g) were selected aleatory distributed in 15 circular tanks (triplicate for the group) and fed test diets for 56 days. The outcomes revealed that the supplementation of SPE up to 1 g kg-1 failed to show significant differences in the organosomatic indices as compared to the control group. The most inferior protein value of dress-out fish composition was observed in the fish fed the control diet, which was statistically lower than the SCP0.1 group (p < 0.05), while no significant difference was observed in other macronutrient composition among the treatments. Total monounsaturated fatty acid (MUFA) had lower trend in the carcass of fish fed SPE supplemented diets, so that lowest MUFA were observed in SPC0.05 group (p < 0.05; 25.22 ± 4.29%). The lowest value of docosahexaenoic acid was observed in the control diet compared to the SPE -supplemented diets (p < 0.05). The serum alternative complement pathway levels in all treatments tend to promote compared to the control treatment. A similar trend was observed for lysozyme activity. According to the results, the superoxide dismutase (SOD) value were highest in SPC0.05 and SPC0.1 compared to the other treatments (p < 0.05), while a further elevation of the SPE Padina sp. extracted level (SPP0.1 ) leads to a decrease in SOD value. Thiobarbituric acid reactive substances of plasma was indicated not to influence by sulfated polysaccharide extracts in the refrigerated storage. The lowest serum stress indicators were observed in fish fed SPP0.05 group postchallenge test. Taken together, our outcomes revealed that SPE of two species of seaweeds bestows benefits in some of the immunity and antioxidant system. Also, notable elevations in HUFA were observed in juvenile rainbow trout fed supplemented with SPE .

Trace metals and macrominerals in common seaweeds in the Marchica (a restored lagoon, Mediterranean Sea): Nutritional value and health risk assessment

This study investigated the contents of macrominerals (Na, K, Ca, Mg and P) and essential trace metals (Fe, Mn, Cu, Zn and Se) in four species of seaweeds (Gracilaria sp., Alsidium corallinum, Caulerpa prolifera, and Chaetomorpha sp.) from Marchica Lagoon. The contents of macrominerals with mean values (% dw) can be sequenced in this descending order, [Ca > Mg > Na > K > P] for Caulerpa prolifera, and the decreasing sequence [K > Ca > Mg > P > Na] for Chaetomorpha sp. In red seaweeds, Gracilaria sp. and Alsidiumcorallinum followed these orders: [K > Ca > Na > Mg > P] and [K > Na > Ca > Mg > P] respectively. The essential trace metals mean values (mg kg−1) followed the decreasing order [Fe > Mn > Zn > Cu > Se] for Alsidiumcorallinum, Chaetomorpha sp. and Gracilaria sp., and the following order [Fe > Mn > Zn > Se > Cu] for Caulerpa prolifera. Based on the calculated recommended dietary allowance (RDA), targeted hazard quotient (THQ) and the hazard index (HI), the studied seaweeds did not pose any health risk for human consumption.

Potential of Edible Seaweed of the Kenyan Coast as a Micronutrient Source

Edible seaweed, a rich source of micronutrients, remains underutilized despite its availability at the Kenyan coast, while micronutrient deficiencies remain a major health concern in Kenya. The study assessed micronutrient content of randomly sampled seaweed and consumption patterns, interviewing 175 seaweed farmers and analysing 58 samples from Mombasa, Kilifi, and Kwale counties. Micronutrients (vitamin A, D, B9, B12, iron, zinc, iodine) and heavy metals (mercury, lead, arsenic, cadmium) were measured. Predominantly female seaweed farmers, aged 30-40, with low income and education levels, focused on commercial farming over personal consumption due to limited nutritional awareness. A diverse array of edible seaweed species was identified; 11 Phaeophyceae (Sargassum, Turninaria, Dictyota, Padina, Eucheuma), 9 Chlorophyta (Ulva, Caulerpa, Eucheuma) and 8 Rhodophyta (Gracilaria, Hypnea, Soliera, Eucheuma). Significant regional and species variations were observed; Kilifi samples had higher vitamin A (p= 0.031), D (p=0.047), B9 (p=0.006), Kwale exhibited elevated iron levels (p= 0.047). Green phyla showed higher vitamin B12, D, zinc, iodine levels, while red phyla were rich in vitamin B9, A, and iron. Eucheuma cotonii had the highest vitamin B12 (696.6 μg/100 g) and vitamin A (298.6 μg/100 g) levels, Ulva intestinalis recorded highest iron (637.85 mg/kg) and Caulerpa taxifolia had highest zinc (277.74 mg/kg). Though some species contained traces of lead and cadmium within permissible limits, mercury was found in only four species, with no arsenic detected. Increasing awareness of seaweed's nutritional value is crucial to combatting micronutrient deficiencies, alongside further research into processing, value addition, market integration, and heavy metal mitigation strategies. Keywords; Edible seaweed, Micronutrients, Micronutrient deficiencies, Kenyan coast

In silico molecular docking of cyclooxygenase (COX-2), ADME-toxicity and in vitro evaluation of antioxidant and anti-inflammatory activities of marine macro algae.

The marine ecosystem harbors unique and diverse bioactive compounds that can offer a vast repertoire of molecules with therapeutic properties. In the present study, four different species of red marine seaweeds were analyzed for its phytoconstituents and the potent antioxidant and anti-inflammatory activity of the methanolic extracts were screened and determined. The results revealed that, among the 4 samples, G. corticata, scored a good antioxidant potential by DPPH (67.61 ± 1.23%, IC50 = 577.7µg) and metal chelation assay (29.40 ± 0.32%, IC50 = 1684µg). The anti-inflammatory analysis has shown that, H. dialata was found to exhibit maximum inhibition against the albumin denaturation (83.50 ± 0.24%), whereas G. corticata was observed to measure a maximum inhibition in heat-induced hemolysis (60.40 ± 0.46%) and proteinase inhibition assay (83.30 ± 0.18%). An extensive literature survey was carried out for the bioactive compounds in G.corticata; it was examined for drug likeliness by ADME analysis and toxicological parameters. Further, the best selected bioactive compounds were subjected to in silico molecular docking with pro-inflammatory target, cyclooxygenase (COX-2). Hexadecanal and Neophytadiene were reported to obtain the highest binding affinity (-5.3) for COX-2 enzyme. Hence, in silico molecular docking studies had shown that G. corticata was found to possess potential anti-inflammatory activity that can prevent conversion of arachidonic acid to prostaglandins by inhibiting COX-2. In addition, molecular dynamic simulation studies have shown the stability of Hexadecanal-6COX complex. To conclude, the outcomes of the present study may shed light on the understanding of the usage of bioactive compounds for therapeutic purpose.

Deep Learning in Chinese Text Information Extraction Model for Coastal Biodiversity

In the coastal areas of China, scientists have collected nearly 500 species of coastal plants and seaweeds. The collected information includes species description, morphological characteristics, habitat distribution and resource value of plants in China. By effectively extracting Chinese text information, this article establishes a Chinese text information extraction model based on DL. This article is based on short-term and short-term memory artificial neural networks for short text classification. In addition, this article also integrates the L-MFCNN models of MFCNN for short text classification. Comparing the two methods with traditional text recognition algorithms, information extraction based on syntax analysis and deep learning, the results show that, compared with the comparison method, the recognition accuracy of Chinese text information of this neural network model can reach 96.69%. Through model training and parameter adjustment, Chinese text information of coastal biodiversity can be quickly extracted, and species categories or names can be identified.

Characteristics of powder agar extracted from different seaweeds species and locations in Indonesia

Characteristics of powder agar extracted from different seaweeds species and locations in Indonesia

Oral administration of terpenoids and phenol fraction of Padina gymnospora stimulates the nonspecific immune response and expression of immune genes, and protects the common carp (Cyprinus carpio) from experimental Aeromonas hydrophila infection

Common carp (Cyprinus carpio), a valuable aquaculture species susceptible to various infections, requires effective immune enhancement strategies. This study investigates the immunomodulatory effects of orally administered terpenoids and phenol fraction (TPF) from Padina gymnospora in C. carpio, focusing on stimulation of nonspecific immune response, immune gene expression, and protection against experimental infection. P. gymnospora is a brown seaweed species known for its bioactive compounds and medicinal properties. TPF was extracted using the Harborne fractionation method, and the presence of terpenoids and phenol compounds was confirmed by qualitative analysis and high-performance thin layer chromatography (HPTLC). TPF was administered orally in different doses to carp. Nonspecific immune responses were evaluated by measuring cellular ROS, RNI, and peroxidase production. The expression of immune genes (lysozyme and interleukin-1β) was assessed by reverse transcriptase PCR. Furthermore, the protective efficacy of TPF was determined by infecting carp with a virulent pathogen, Aeromonas hydrophila, and monitoring mortality rates and disease symptoms. The results demonstrate that oral TPF administration significantly enhances nonspecific immune responses, with increased ROS, RNI, and peroxidase production, indicating improved immune function. Expression levels of lysozyme and interleukin-1β were upregulated, suggesting immune system activation. Moreover, TPF exhibited significant protection against experimental infection, with lower mortality rates compared to the control group. These findings highlight TPF's potential as an effective immunostimulatory agent, enhancing immune responses and providing infection protection in carp. In conclusion, oral TPF administration stimulates nonspecific immune responses, modulates immune gene expression, and confers protection against experimental infection in carp, displaying its potential for enhancing immune responses and disease resistance in aquaculture species, and contributing to sustainable fish health management.

Polysaccharides from red seaweeds: Effect of extraction methods on physicochemical characteristics and antioxidant activities

Seaweed polysaccharides are reported to possess biological and medicinal properties. Specifically, the antioxidant activity of seaweed extracts is the subject of intensive research due to ever-increasing demands from the food and pharmaceutical industries. The structure and composition of polysaccharides (carrageenan, xylan) extracted from four red seaweed species: Chondrus crispus (CC), Ahnfeltiopsis devoniensis (AD), Sarcodiotheca gaudichaudii (SG) and Palmaria palmata (PP) were compared and correlated with their antioxidant activity. Crude polysaccharide extracts were characterized by NMR (1H and 13C), HPLC-SEC, and FTIR spectroscopy. Total phenolic content (TPC), total sugars, sulfate and protein content were determined using spectrophotometric methods. The antioxidant capacity of each fractionated polysaccharide sample was evaluated by the following methods: DPPH (2,2-diphenyl-1-picrylhydrazyl radical), ABTS (2,2-azino-bis-[3-ethylbenzothiazoline-6-sulfonic acid]), superoxide dismutase (SOD), ferric-reducing power in FRAP (Ferric-reducing Antioxidant Power) assays, and the hydroxyl radical (OH) scavenging capacity assay. The highest antioxidant activity was found in extracts from A. devoniensis (ι/κ hybrid carrageenan), while the lowest was in P. palmata (xylans). Moreover, Chondrus crispus extracts did not possess SOD inhibition activity. Polysaccharides evaluated in this study offer high potential for applications in the food, pharmaceutical and biotechnology industries.

Analysis and health risk assessment of heavy metals in four common seaweeds of Marchica lagoon (a restored lagoon, Moroccan Mediterranean)

The Marchica lagoon (Morocco, Mediterranean) is a wetland classified as a RAMSAR site, which has been the subject of restoration activities after several years of pollution. The heavy metal (loïdes) content was studied in four common species of seaweed (Gracilaria sp., Alsidium corallinum, Caulerpa prolifera and Chaetomorpha sp.) for the first time, and was added to the basic studies carried out on sediments and water of this ecosystem. The heavy metals with mean values (mg/kg) can be sequenced in descending order, Al > Sr > Rb > Ba > As > Ti > V > Ni > Pb > Cr > Cd > Li > Co for Chaetomorpha sp., and the following order Al > Sr > As > Pb > Ti > Ba > Rb > V > Li > Cr > Co > Ni > Cd for Caulerpa prolifera. The mean concentrations (mg/kg) in Gracilaria sp. followed the sequence Al > Sr > Ti > Rb > Pb > As > Co > Ba > V > Ni > Cr > Li > Cd, and the following order Al > Sr > Ti > Rb > As > Ba > Pb > V > Co > Ni > Cr > Li > Cd in Alsidium corralinum. The Pb and As levels in studied seaweeds were above the CEVA standards. The health risk analysis showed that consuming the seaweed under study posed a serious risk. All examined seaweed had HI values greater than 1.0, and arsenic is the element that strongly contributes to these values, which can suggest a potential negative impact caused by this metalloid. Red seaweeds showed the highest MPI, followed by green seaweeds.

Role of ABC Proteins in Secondary Metabolism and Immune (=Defensive) Response in Seaweeds.

Laurencia seaweed species synthesize a broad range of secondary metabolites, mainly terpenes (e.g., elatol), exhibiting diverse ecological roles, such as defense against fouling and herbivores. Recently, an intricate cellular machinery was described concerning terpenes biosynthetic pathways, storage inside corps en cerise (CC), and regulated exocytosis in these species. But for seaweeds in general, the proteins involved in transmembrane transport of secondary metabolites remain unknown. Assays with Rhodamine-123 and cyclosporine A (CSA) revealed the presence of ABC transporters in CC membrane of Laurencia dendroidea. In vivo incubation assays with CSA resulted in CC morphological changes, reduced intracellular elatol concentrations, and increased biofouling cover on the seaweed surface. Cultivation assays in the presence of a marine pathogenic bacteria induced the expression of ABC proteins belonging to the subfamilies ABCB, ABCD, ABCF, and ABCG. The latter subfamily is known to be associated with the transport of plant terpenes. Our results shed new light on the role of ABC proteins in key mechanisms of the defensive system in seaweeds against fouling and herbivory.

Australian brown seaweeds as a source of essential dietary minerals

Seaweeds are rich in essential dietary minerals, often lacking in terrestrial plant foods, with interest in Australian seaweeds rapidly increasing. We screened six Australian brown seaweeds with commercial potential for dietary mineral composition: Cystophora torulosa, Caulocystis uvifera, Durvillaea potatorum, Ecklonia radiata, Hormosira banksii and Phyllospora comosa. Spatial replicates of each species were collected from three non-urbanised sites remote from pollution sources and processed for human consumption. Dried samples were analysed by inductively coupled plasma mass spectrometry (ICP-MS) for 12 essential dietary minerals. Overall dietary mineral composition differed significantly amongst all species, except between sargassaceous species C. torulosa and C. uvifera; but concentrations of individual elements varied in complex ways. All species investigated had high concentrations of dietary minerals essential for optimal human health if consumed in realistic quantities (e.g. 10 g day−1 DW) as part of balanced diets, including the most common dietary minerals deficient in humans (iodine, iron, zinc, magnesium, calcium and selenium): iodine (888 ± 100 mg kg−1 DW) and zinc were highest in P. comosa; iron and calcium were highest in C. torulosa, but calcium was also high in E. radiata, H. banksii and D. potatorum; magnesium was highest in H. banksii, D. potatorum and P. comosa; selenium concentrations exceeded those previously reported for seaweeds for all species, except D. potatorum. The best nutritional outcomes may be achieved by regularly consumption of a diversity of seaweed species. However, further investigation into ways to reduce iodine content in some species may be required to maximise health benefits from regular consumption of these Australian seaweeds.

Elements and sugars in kelp and fucoid species in Greenland, correlation and seasonality

Greenland seaweeds constitute an arctic marine resource as well as being important monitoring organisms in connection with arctic mining activities. In both cases, the natural element content, and its potential seasonal variation, is important knowledge for designing a monitoring programme and for planning of harvest for highest biomass quality and value. Therefore, concentration levels of 54 elements and two sugars (laminarin and mannitol) were obtained in seven different seaweed species of relevance for monitoring and commercial harvest sampled in the same location in Greenland across all seasons during two years. The kelp species sampled were Agarum clathratum, Alaria esculenta, Hedohyllum nigripes, Saccharina latissima, and the fucoids Ascophyllum nodosum, Fucus distichus and F. vesiculosus. The thallus samples were analysed for element concentration levels by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and the monosaccharides were separated by HPAEC ion exchange and detected using Pulsed Amperometric Detection (gold electrode). The results showed, in the studied location, and on average, that the dominant major and minor elements are potassium, sodium, calcium, magnesium and phosphorus with mean concentration levels > 4800 μg g−1. The trace elements are dominated by iron, aluminium and arsenic with mean concentration levels > 61 μg g−1. Concentration levels of elements were in general seaweed species specific. Seasonality was not tested statistically significant for most of the elements when data were pooled in summer and winter months, although higher concentration levels during winter could be observed. Thus, the content of laminarin and mannitol is highest during late summer, thus July–October/November may be the time window for optimal harvest yield with respect to those compounds, although narrower time windows may be considered, depending on the species harvested. Regarding unwanted compounds such as As and I, harvesting time of the year seems not to cause a profound difference on the quality of the biomass.

Genetic resources of macroalgae: Development of an efficient method using microsatellite markers in non-model organisms

Red and brown seaweeds are species with high ecological and economic importance. Here we report the feasibility of cost-effective molecular marker development in 6 species from different phyla. Microsatellite markers of two brown seaweed species Alaria esculenta and Pylaiella littoralis, and of four red seaweed species Calliblepharis jubata, Gracilaria gracilis, Gracilaria dura and Palmaria palmata were identified and characterized in genomic sequences obtained using Double-Digest Restriction site Associated DNA (ddRAD). A total of 64,623,186 reads were generated from two runs of multiplexed Illumina Miseq sequencing, from which 30,636 reads containing microsatellite motifs including 15,443 where primer pairs could be designed. Five hundred seventy-six primers pairs were selected for amplification trials to determine levels of polymorphism. Of these 576 loci, 338 could be amplified and 142 of the 338 loci were polymorphic. A total of 28 usable polymorphic markers were developed in A. esculenta, 18 in P. littoralis, 11 in C. jubata, 14 in G. gracilis, 21 in G. dura and 13 in P. palmata. The overall number of alleles per locus ranged from 2 to 22. These 105 new microsatellite markers will be useful for further studies of population genetics, breeding programs and conservation genetics of these species. Compared with traditional approaches, our study yielded thousands of microsatellite loci for six different species in a short time and with affordable costs. This study, based on the use of ddRADseq, provided preliminary data about the genetic structure and reproduction mode of these six non-model species based on a small number of individuals from two geographically-distant populations and on the genetic structure and reproduction mode of two non-model species, i.e. detection of clonality for two red algae, C. jubata and G. dura and detection of highly genetically divergent populations corresponding probably to different cryptic species under the name P. littoralis.

Ocean acidification reduces thallus strength in a non-calcifying foundation seaweed

Climate change is causing unprecedented changes in terrestrial and aquatic ecosystems through the emission of greenhouse gases, including carbon dioxide (CO2). Approximately 30% of CO2 is taken up by the ocean ('ocean acidification', OA)1, which has profound effects on foundation seaweed species. Negative physical effects on calcifying algae are clear2, but studies on habitat-forming fleshy seaweeds have mainly focused on growth and less on thallus strength3,4. We exposed the habitat-forming brown seaweed Fucus vesiculosus to OA corresponding to projected climate change effects for the year 2100, and observed reduced apical thallus strength and greater loss of exposed individuals in the field. The tissue contained less calcium and magnesium, both of which are important for creating structural alginate matrices. Scanning electron microscopy (SEM) revealed tissue voids in the OA samples that were not present in seaweeds grown under ambient pCO2. We conclude that under OA, weakened F. vesiculosus will be at a significantly higher risk of physical damage and detachment.

Nutritional, physicochemical, and sensory characterization of four common Northern European seaweed species intended for food

Seaweed is depicted as a future food in Western cultures, yet its introduction and expansion to new markets come with several challenges, including food neophobia and limited knowledge about its usability. To address these challenges, this study characterizes sensory perceptions, nutritional content, and physicochemical properties of four common northern European seaweed species, Saccharina latissima, Alaria esculenta, Palmaria palmata, and Ulva sp. These species are rich in minerals (25.8–36.8 %) and carbohydrates (29.6–54.6 %), especially dietary fibre (29.8–34.1 %), but have lower levels of dietary protein (6.7–11.4 %) and lipids (1.3–2.4 %). The amino acid profiles almost matched those of complete proteins, but with lower levels of histidine (Ulva sp. had also lower levels of lysine). All species were generally perceived to have high taste of saltiness, medium umami, low bitterness and sourness, and no sweetness. Overall, P. palmata stood out most from the other species with its red magenta colour, sea and shellfish odour, umami taste, and firm and chewy texture. Contrary, Ulva sp. was perceived as the saltiest species, with a lightness in colour and elements of yellow, an odour resembling lemon and fresh grass, and the least crispy, firm, and chewy texture. The two brown species, S. latissima and A. esculenta, were overall perceived as similar to each other. The mapping of seaweed's attributes in this study can be directly useful as knowledge for the improvement of future seaweed products and their availability in Western food cultures.

Exploring alternative red seaweed species for the production of agar-based hydrogels for food applications

Three different red seaweed species, Gelidium corneum and two Gracilaria species (Agarophyton chilensis, and Gracilariopsis longissima), were used to produce agar-based fractions through conventional and simplified extraction methods and their composition and gel-forming properties were evaluated. The use of an alkaline pre-treatment was effective in removing impurities such as proteins, lipids, and ash, while the agarose/agaropectin ratio in agar was not affected. This led to the formation of hydrogels with higher stiffness and strength. Surprisingly, the presence of semi-crystalline agaropectin in the agar fractions from the two Gracilaria species, especially G. longissima, promoted the formation of more densely packed and stronger hydrogel networks, with higher gelling temperatures and superior mechanical properties. Thus, these results suggest that G. longissima has the potential to be used as an alternative to the more widespread use of G. corneum for the production of agar hydrogels for food applications.