Ulva Rigida Research Articles

Ulva species from the Romanian Black Sea Coast – between green blooms and nature’s contribution to people

Ulva species have a worldwide distribution and remarkable ability to develop under various conditions, being considered an important natural resource that is under-exploited along the Romanian Black Sea coast. These green algae, involved in green tides observed worldwide, have also a remarkable potential as prolific sources of bioactive compounds with potential health benefits and a wide range of applications in food, feed, pharmaceutical, nutraceutical, cosmetic, or biofuel industries. The study aims to analyze the quantitative variability of Ulva spp. during 2019 - 2023, in order to highlight the areas with algal agglomerations. These are also areas where potential algal deposits can develop during summer season. This fresh biomass can be selectively collected and valorized, thus supporting the circular economy. The sampling method was the classic one (square method/20x20 cm) from 14 stations along Pescarie towards Vama Veche, at depths between 0 to 3 m deep. Among all Ulva spp., Ulva rigida and Ulva intestinalis quantitatively distinguished during the study period, being also the main components of algal deposits. The highest mean wet biomasses were recorded in the southern part, as follows: U. rigida – a maximum value of 2200 g/m2 at 2 Mai; U. intestinalis – max. value of 700 g/m2 at Eforie South. Furthermore, a review of species’ main bioactive compounds, emphasizing their potential health benefits, will also be provided.

Evaluation of the ecological quality of the macroalgal communities along the Algerian coast (Algeria, Mediterranean Sea)

The assessment and preservation of the marine environment, particularly coastal ecosystems, has emerged as a global priority. In this study, the rocky bottom quality (CFR) index, which is based on macroalgae composition and abundance, was used to assess the ecological quality of coastal waters at six sites along the Algerian coast that represent a wide range of anthropogenic pressures. The sensitivity of the CFR index to the anthropogenic pressure index (MALUSI) was also assessed. Multivariate analyses (DCA, nMDS, cluster, SIMPER, and PCA) were used to assess the variability of macroalgal community structure. The CFR index calculated for this study was compared to the EEI-c and CARLIT indices. The CFR index classified the study sites based on ecological quality: good to high quality in the western sites (Ténès, Kouali1, and Kouali2) and moderate quality in the central sites (Fontaine, Fort de l’eau, and Surcouf). The findings indicate that the CFR and MALUSI indices are highly correlated. The abundance and composition of macroalgal communities are useful indicators of rocky shore quality, as demonstrated by structural analyses of characteristic macroalgae and opportunistic species. The competitive characteristic macroalgae of the Cystoseira sensu lato species were found to be associated with sites of good and high ecological quality. Stress-tolerant characteristic macroalgae (Pachymeniopsis lanceolata, Ellisolandia elongata, and Halopteris scoparia) and opportunistic ruderal species (Ulva rigida, Ulva lactuca, and Ulva linza) were found in sites with moderate ecological quality. The CFR index was compared with the EEI-c and CARLIT indices, and it can be noted that the three indices use different spatial scales, biological levels and species classifications. Therefore, CFR, EEI-c, and CARLIT indices are useful tools for assessing the quality of coastal waters.

Mechanism of up-regulated H2O2 BPA-derived production and production of (poly)phenols by two seaweeds of the genus Ulva.

The present study provides information on the effects of BPA on ROS production-related phenomena in the chlorophytes Ulva rigida and U. intestinalis, and on the mechanism they establish against BPA toxicity, at environmentally relevant concentrations (0.1-3 μg L-1). Up-regulated H2O2 generation seems to be a key factor causing oxidative damage. Interspecific differences, in terms of the mechanism and the temporal response to BPA toxicity were observed. BPA effects on U. rigida were more intense and appeared earlier (on 1D at 0.1 μg L-1) compared to U. intestinalis and mostly after 7D (LOEC: 0.3 μg L-1, Terminal time, Tt: 7D). In U. rigida, on 1-5D, the 'mosaic' type effect patterns ('models' 3A/3B) with 'unaffected' and 'affected' areas (dark content, positive H2DCF-DA staining signal/H2O2 production and chlorophyll autofluorescence signal loss) indicated a time-dependent manner. After 7D, only U. rigida cells with dark content formed aggregates, showing positive H2O2 production ('model' 4) or in some cells oxidative damages triggering retrograde signaling in the neighboring 'unaffected' areas ('model' 5). H2O2 overproduction (CTCF ratio) in U. rigida, on 1D at the lowest concentration and after 7D at 0.3-1/3 μg L-1, respectively, seems to stimulate (poly)phenolic production, in a dose- and time-dependent manner. U. intestinalis did not display severe BPA impact (i.e., 'models' 4, 5) at any exposures, although at a later time indicated a lower LOEC (0.1 μg L-1, Tt: 9D) than that in U. rigida. In U. intestinalis, H2O2 production does not appear to stimulate high (poly)phenolic amounts.

Effects of Individual and Combined Applications of Seaweed Extracts and Plant Growth-Promoting Rhizobacteria (PGPR) on Plant Growth and Physio-Biochemical Properties of Soft Wheat and Faba Bean

ABSTRACT The research on carbon materials and plants primarily focuses on their use in soil, showing variable effects. However, significant gaps exist regarding their impact under stress conditions (such as drought, salinity, etc.) and their interactions with plant physiological processes. Long-term effects on plant health and ecosystems are understudied, as are their interactions with other biofertilizers like algae extracts and plant growth-promoting rhizobacteria (PGPR). The aim of the present study was to evaluate the effects of seaweed extracts and PGPR on plant growth and some physio-biochemical properties of soft wheat (Triticum aestivum L.) and faba bean (Vicia faba L.). Two concentrations of aqueous extract from two seaweeds, Fucus spiralis (F) and Ulva rigida (U), and the PGPR bacillus strain solution S48 (S48S) were used either individually or in combination. All treatments were applied as foliar sprays. The findings showed that the combined application of Fucus spiralis extract [25%] (F), Ulva rigida extract [50%] (U), along with the PGPR S48 bacillus strain solution (S48S) promoted plant growth (50.93 cm for faba bean) and root development (17.90 cm for wheat). This treatment also resulted in increased chlorophyll content (3.25 mg/g Fresh Weight (FW) in soft wheat and 3.93 mg/g FW in faba bean), proteins (14.66 µg/mg FW in soft wheat and 23.79 µg/mg FW in faba bean), amino acids (0.46 mg/g FW in soft wheat and 0.56 mg/g FW in faba bean), and total carbohydrates (529.8 µg/ml in soft wheat and 340.7 µg/ml in faba bean) as compared to controls. On the other hand, the nitrate reductase activity was enhanced by seaweed extract application in both crops. Phosphorus (P) uptake by soft wheat and faba bean was significantly improved following the application of Ulva rigida extract [50%] (U), the PGPR S48 bacillus strain solution (S48S), and the co-treatment of Fucus spiralis extract [25%] (F) with the PGPR S48 bacillus strain solution (S48S). The findings suggest that the combined application of Fucus spiralis extract (F) and Ulva rigida extract (U) with the PGPR S48 bacillus strain solution (S48S) can significantly improve plant growth and nutrient absorption in durum wheat and faba bean. This offers a sustainable alternative to chemical fertilizers, reducing pollution and promoting healthier ecosystems. Furthermore, these biological treatments enhance plant resilience to abiotic stresses, potentially increasing yields in challenging conditions. By reducing reliance on chemical fertilizers, these practices can save money for farmers and advance sustainable agriculture.

In vitro evaluation of algae and their effect as dietary ingredient on growth, chemical composition and intestinal functionality in juvenile turbot (Scophthalmus maximus)

The objectives of this study were to evaluate the in vitro protein hydrolysis of five algae (Arthrospira sp., Chlorella sp., Tisochrysis sp., Microchloropsis sp. and Ulva rigida) by the digestive proteases of Scophthalmus maximus, and to assess the effect of feeding turbot juveniles on diets supplemented with these algae in a 60-day feeding trial. The in vitro results revealed that algal protein was hydrolysed by turbot digestive proteases. Besides, the quantification of total amino acids released during the in vitro hydrolysis evidenced noticeable amino acid bioavailability, mainly in the case of Arthrospira sp. with up to 42.7% of the amino acids released after 120 min of in vitro hydrolysis. However, the structural characteristics of cell wall of each species influenced the protein accessibility as evidenced by the lower values obtained in Microchloropsis sp. For the in vivo feeding trial, 255 specimens of turbot, with an average initial weight of 26.4 ± 7.6 g, were used, and were fed with diets including 5% and 10% of a blend of the same microalgae tested in vitro (M5 and M10) or U. rigida (U5 and U10), compared to a control feed without algal biomass (CT). At the end of the feeding trial, growth performance and nutrient utilization did not show differences among the experimental groups. In addition, the fish fed with the diets supplemented with algae showed lower lipid oxidation in the muscle, and an improvement in digestive functionality, as the activity of pancreatic and intestinal enzymes increased. The ultrastructural study of the intestinal mucosa revealed an increase in the length of the microvilli and the absorptive surface in fish fed with the algae-supplemented diets, as well as decreased thickness of the lamina propria and the number of goblet cells. These results confirmed that the supplementation of turbot juvenile diets with low percentage of microalgae or U. rigida is appropriate for improving digestive functionality, as well as reducing the oxidation of lipids in the muscle.

Element composition of several marine macrophytes (Crimea, Black Sea) and correlations with the element abundances in sediments and seawater

The study of the element accumulation in marine plants against the backdrop of permanently increasing environmental pollution is of particular importance due to the participation of these plants in biogeochemical cycles. The element abundances are highly variable and depend on both the macrophyte species and environment. The purpose of this study was to analyze the elemental composition of widespread marine plants of different taxonomic affiliations collected in the same area of the Black Sea coast. The contents of 74 elements in three species of lower (red, brown, green algae) and one species of higher plants (seagrass) were analyzed using inductively coupled plasma mass spectrometry. High contents of most elements were found in the red alga Ceramium ciliatum and in rhizomes of the seagrass Zostera noltei. In C. ciliatum, high metal bioaccumulation factors were found, which are dependent also on their concentration in the environment. Compared to the higher plant, all the macroalgae accumulated increased amounts of As and I. The seagrass proved to be a good concentrator of Mo and Sb, and relatively high contents of Mn, Co, Ni, Zn, Cd and Ir were registered in its leaves. High contents of Mg, S, Ge, Se and Ta were found in the green alga Ulva rigida, and elevated levels of Al, As, Sr, Zr, Ru, Rh, Pd, Ag, Ba and Re were noted in the brown alga Gongolaria barbata. The enrichment factors for most elements in the sediments were well above 1 with respect to both the local Late Pleistocene sediments and the upper continental crust. The strength of correlations between the element contents in the plants and sediments was found to decrease with the specific surface area growth and appeared to have a lower asymptotic limit of the sediments–seawater correlation strength.

Haliotis tuberculata coccinea grow-out performances according to diet and production systems

ABSTRACT Haliotis tuberculata coccinea is a candidate of growing interest to diversify aquaculture in the Canary Islands, principally based on fish production, to improve aquaculture development opportunities. The economic viability of commercial abalone farming depends largely on the rearing system employed and the feeding sources employed during the grow-out culture period. We studied the effects of two land-based culture systems on the growth performance of abalone and the nutritional quality of their tissues, in a crossed design. Recirculated (RAS) and open flow (FLOW) culture systems were compared. Fresh macro algae (FMA) (Gracilaria cornea and Ulva rigida) were compared to manufactured compound feed (CF) and a mixture of both (MIX). Survival rates were high (97–100%) regardless the treatments tested. MIX and FMA diets produced the best results for Shell Growth Rate, Specific growth rates for shell growth (SGRsl) and weight (SGRw) as well as Food Conversion Ratio (FCR). The highest value for feed intake was recorded for the MIX diet. A positive relationship has been observed between the amounts of protein and lipids in diets and the disposition of these in the viscera of animals fed such diets. The rearing system used had no significant effect on growth and nutritional parameters.

Valorization of Gelidium corneum by-product through solid-state fermentation

Red seaweed Gelidium is used for agar extraction, generating large quantities of by-products (red seaweed by-product – GBP). Its carbohydrate and protein-rich composition makes it a suitable substrate to produce value-added compounds through solid-state fermentation (SSF). For the first time, GBP was used in SSF with Aspergillus ibericus and Aspergillus niger for carbohydrases production and protein enrichment. SSF was performed with unsupplemented GBP, supplemented with Mandel salt solution, and mixed at equal dry mass proportion with plant feedstuffs and with the seaweed Ulva rigida. A. niger CECT 2915 was the best strain under SSF obtaining the maximum xylanase activity (498 ± 49 U g-1), in GBP mixed with sunflower cake and the maximum of cellulase activity (382 ± 37 U g-1) in GBP mixed with rapeseed cake. In these mixtures, protein content increased 1.2-fold by SSF, as well as in GBP mixed with rice bran (1.3-fold). Scale-up of SSF using GBP mixed with sunflower cake from flasks to tray-type bioreactors demonstrated SSF reproducibility, achieving similar xylanase and cellulase activities. In the stirred-drum bioreactor, aeration and low agitation favored both enzymes production. Bioprocessing of GBP with plant feedstuffs using SSF was a cost-effective strategy to produce high-value enzymes, valorizing this seaweed by-product.

Physicochemical properties and in vitro prebiotic activity of Ulva rigida polysaccharides

The physicochemical properties and prebiotic potential of polysaccharide extract from the green seaweed Ulva Rigida were explored. The UPS PII-1 fraction purified by DEAE-Sephacel and Sephacryl S-400 columns was identified as a high molecular weight heteropolysaccharide (1.63 × 103 kDa) composed of rhamnose, glucose, mannose, galactose, arabinose, and fructose. FTIR analysis showed typical absorption bands of the structure of ulvan polysaccharides. In vitro prebiotic studies revealed that U. rigida polysaccharides (UPS) were highly resistant to gastric and intestinal juice hydrolysis. UPS also enhanced the growth of probiotic bacteria including Bifidobacterium and Lactobacillus as a potential source of prebiotics in functional food.

Extraction, Characterisation and Evaluation of Antioxidant and Probiotic Growth Potential of Water-Soluble Polysaccharides from Ulva rigida Macroalgae.

Ulva rigida green macroalgae contain a variety of polysaccharides. A recent study investigated the optimum concentration and yield of polysaccharide extraction from oven-dried U. rigida biomass using a water-soluble polysaccharide extraction method that adhered to safety standards. This study utilised complete factorial experiments to examine the effects of varying factors on polysaccharide extraction. Results showed a positive correlation between increased levels of all factors and higher polysaccharide extraction yield. This study also found that the main factors and their interaction had a significant impact on the extracted polysaccharides from U. rigida. The highest polysaccharide content and yield were 9.5 mg/mL and 189 mg/g, respectively. Water-soluble polysaccharides demonstrated the presence of reducing sugar (8 mg/g), phenolics (0.69 mg/g) and flavonoids (1.42 mg/g) and exhibited antioxidant properties. Results revealed that freeze-dried polysaccharide powders were primarily composed of the monosaccharide rhamnose. Preliminary results on the effect of these powders on probiotics demonstrated that supplementation of polysaccharides from U. rigida promoted viable Lactobacillus rhamnosus ATCC 53103 growth during cultivation. This discovery has the potential to revolutionise the human food industry and promote the development of functional ingredients for novel and future food products, with numerous applications in the nutraceutical and pharmaceutical industries.

Unveiling the Antioxidant Potential of Halophyte Plants and Seaweeds for Health Applications

Halophyte plants and seaweed are described in the literature as rich sources of antioxidant compounds that can be used in the pharmaceutical and food industries. In this work, we studied the antioxidant composition of five species of halophytic plants (Suaeda vera Forssk, Portulaca oleracea L., Inula crithmoides L., Salicornia ramosissima (Hook.f.) J. Woods and Sarcocornia perennis (Mill.) A.J.Scott) and three seaweeds (Gracilaria gracilis (Stackhouse) Steentoft, L.Irvine and Farnham, Fucus spiralis L. and Ulva rigida C. Agardh) collected in Sado Estuary, Portugal. In the case of the plants, different parts of the plant were also assessed. Various extraction procedures were also performed to understand which methods were most suitable for extracting the various antioxidant compounds. Therefore, the aim of this study was to characterize the antioxidant compounds in halophytes and seaweed using various methods (ABTS, DPPH and FRAP), as well as the phenolic (TPC) and flavonoid (TFC) contents in the different extracts obtained. The amount of soluble protein in each extract was also determined. The results show that methanolic extracts generally have a higher antioxidant capacity, while the highest soluble protein content was observed in aqueous extracts. The seaweed Fucus Spiralis showed the highest antioxidant content, while in halophytic plants the highest antioxidant content was detected in the leaves. In general, this work confirms the potential of halophytes and seaweed as sources of antioxidant compounds for use in the food and pharmaceutical industries.

Photoprotection by photoinhibitory and PSII-reaction centre quenching controls growth of Ulva rigida (Chlorophyta) and is a pre-requisite for green tide formation

Main ConclusionThe combined photoinhibitory and PSII-reaction centre quenching against light stress is an important mechanism that allows the green macroalga Ulva rigida to proliferate and form green tides in coastal ecosystems.Eutrophication of coastal ecosystems often stimulates massive and uncontrolled growth of green macroalgae, causing serious ecological problems. These green tides are frequently exposed to light intensities that can reduce their growth via the production of reactive oxygen species (ROS). To understand the physiological and biochemical mechanisms leading to the formation and maintenance of green tides, the interaction between inorganic nitrogen (Ni) and light was studied. In a bi-factorial physiological experiment simulating eutrophication under different light levels, the bloom-forming green macroalga Ulva rigida was exposed to a combination of ecologically relevant nitrate concentrations (3.8–44.7 µM) and light intensities (50–1100 µmol photons m−2 s−1) over three days. Although artificial eutrophication (≥ 21.7 µM) stimulated nitrate reductase activity, which regulated both nitrate uptake and vacuolar storage by a feedback mechanism, nitrogen assimilation remained constant. Growth was solely controlled by the light intensity because U. rigida was Ni-replete under oligotrophic conditions (3.8 µM), which requires an effective photoprotective mechanism. Fast declining Fv/Fm and non-photochemical quenching (NPQ) under excess light indicate that the combined photoinhibitory and PSII-reaction centre quenching avoided ROS production effectively. Thus, these mechanisms seem to be key to maintaining high photosynthetic activities and growth rates without producing ROS. Nevertheless, these photoprotective mechanisms allowed U. rigida to thrive under the contrasting experimental conditions with high daily growth rates (12–20%). This study helps understand the physiological mechanisms facilitating the formation and persistence of ecologically problematic green tides in coastal areas.

Microplastic accumulation and ecological impacts on benthic invertebrates: Insights from a microcosm experiment

Microplastic (MP) pollution poses a global concern, especially for benthic invertebrates. This one-month study investigated the accumulation of small MP polymers (polypropylene and polyester resin, 3–500 μm, 250 μg L−1) in benthic invertebrates and on one alga species. Results revealed species-specific preferences for MP size and type, driven by ingestion, adhesion, or avoidance behaviours. Polyester resin accumulated in Mytilus galloprovincialis, Chamelea gallina, Hexaplex trunculus, and Paranemonia cinerea, while polypropylene accumulated on Ulva rigida. Over time, MP accumulation decreased in count but not size, averaging 6.2 ± 5.0 particles per individual after a month. MP were mainly found inside of the organisms, especially in the gut, gills, and gonads and externally adherent MP ranged from 11 to 35 % of the total. Biochemical energy assessments after two weeks of MP exposure indicated energy gains for water column species but energy loss for sediment-associated species, highlighting the susceptibility of infaunal benthic communities to MP contamination.

Green Macroalgae Hydrolysate for Biofuel Production: Potential of Ulva rigida

In this study, the green macroalgae Ulva rigida, which contains 34.9% carbohydrates, underwent treatment with commercial hydrolytic enzymes. This treatment yielded a hydrolysate that contained 23 ± 0.6 g·L−1 of glucose, which was subsequently fermented with Saccharomyces cerevisiae. The fermentation process resulted in an ethanol concentration of 9.55 ± 0.20 g·L−1. The optimal conditions for ethanol production by S. cerevisiae were identified as follows: non-sterilized conditions, an absence of enrichment, and using an inoculum size of 118 mg·L−1. Under these conditions, the fermentation of the green macroalgal hydrolysate achieved a remarkable conversion efficiency of 80.78%. The ethanol o/t ratio, namely the ratios of the experimental to theoretical ethanol produced, for Scheffersomyces stipitis, Candida guilliermondii, Kluyveromyces marxianus, and S. cerevisiae after 48 h of fermentation were 52.25, 63.20, 70.49, and 82.87%, respectively. Furthermore, S. cerevisiae exhibited the best outcomes in terms of ethanol production (9.35 g·L−1) and conversion efficiency (80.78%) after 24 h (optimal time) of fermentation.

Characterization and Biological Activities of the Ulvan Polysaccharide-Rich Fraction Obtained from Ulva rigida and Ulva pseudorotundata and Their Potential for Pharmaceutical Application.

Seaweed from the genus Ulva (Ulvales, Chlorophyta) has a worldwide distribution and represents a potential biomass source for biotechnological applications. In the present study, we investigated the ulvan polysaccharide-rich fraction (UPRF) isolated from two Ulva species (U. rigida and U. pseudorotundata), naturally occurring on the Spanish Mediterranean coast. Chemical characterization of UPRFs was performed in order to explore the polysaccharides' composition. Biological assessments of UPRFs were compared by antioxidant activity and in vitro toxicity tests in the human cell lines: HCT-116 (colon cancer), G-361 (malignant melanoma), U-937 (leukemia), and HaCaT cells (immortalized keratinocytes). Chemical analysis revealed that both UPRFs presented rhamnose as the major relative sugar constituent, followed by glucose in U. rigida and xylose in U. pseudorotundata. Both also presented glucuronic acid, galactose, ribose, and mannose as the remaining monosaccharides. Similar antioxidant activity was obtained, where we observed increased activity in response to increased polysaccharide concentrations. Both UPRFs presented moderate toxicity against HCT-116 cell lines and a selectivity index ≥ 3, suggesting a good potential for use in pharmaceutical products.

Synergistic activity of Limosilactobacillus reuteri KUB-AC5 and water-based plants against Salmonella challenge in a human in vitro gut model.

A synbiotic is a combination of live microorganisms and specific substrates that are selectively utilized by host microorganisms, resulting in health benefits for the host. Previous studies have demonstrated the protective effects of L. reuteri KUB-AC5 against Salmonella infection in chicken and mouse models. The probiotic activity of L. reuteri KUB-AC5 in these hosts was influenced by nutritional supplements. Water-based plants contain significant amounts of carbohydrates, particularly dietary fiber and proteins, making them potential prebiotic substrates. In this study, four water-based plants (Ulva rigida, Caulerpa lentillifera, Wolffia globosa, and Gracillaria fisheri) were screened for their ability to support the growth of L. reuteri KUB-AC5. Under monoculture testing, U. rigida exhibited the highest capacity to support the growth of L. reuteri KUB-AC5 and the production of organic acids, including acetic acid, lactic acid, and propionic acid (p ≤ 0.05). In co-culture experiments, the synbiotic combination of U. rigida and L. reuteri KUB-AC5 demonstrated the potential to eliminate Salmonella Typhimurium DMST 48437 when inoculated at 104CFU/mL within 9h. The synbiotic activities of U. rigida and L. reuteri KUB-AC5 were further investigated using an in vitro human gut model. Compared to the probiotic treatment, the synbiotic combination of L. reuteri KUB-AC5 and U. rigida showed significantly higher levels of L. reuteri KUB-AC5 (5.1 log copies/mL) and a reduction of S. Typhimurium by 0.8 log (CFU/ml) after 24h (p ≤ 0.05). Synbiotic treatment also significantly promoted the production of short-chain fatty acids (SCFAs), including butyric acid, propionic acid, and acetic acid, compared to prebiotic and probiotic treatments alone (p ≤ 0.05). Furthermore, the synbiotic formulation modulated the in vitro simulated gut microbiome, enhancing putatively beneficial gut microbes, including lactobacilli, Faecalibacterium, and Blautia. Our findings demonstrated that L. reuteri KUB-AC5, in combination with U. rigida, exhibited synergistic activity, as indicated by increased viability, higher anti-pathogenicity toward Salmonella, and the ability to modulate the gut microbiome.

Nutritional Properties, Antioxidant Activity, and Heavy Metal Accumulation in Selected Marine Macro-Algae Species of Sri Lanka

In recent years, the emergence of drug resistance and sensitivity in leading diseases has heightened global interest in natural nutraceuticals as primary health supplements. However, comprehensive scientific scrutiny is essential before marketing these as supplements. In this study, we assessed the nutritional composition, antioxidant activities, and trace metal accumulation in eleven selected Sri Lankan coastal seaweed species. Gracilaria corticata had the highest (p < 0.05) ash and crude fiber content among the species. Protein content ranged from 4.87% to 23.67% (DW), with Ulva rigida displaying the highest (p < 0.05). Crude fat content ranged from 0.09% to 4.13% (DW), with Cladophora herpestica having the highest (p < 0.05) crude fat content. Sargassam cinereum, Turbinaria ornata and Sargassum crassifolium had the highest (p < 0.05) TPC content (51.32 ± 0.61–28.90 ± 2.68 mg/GAE g) and the highest (p < 0.05) radical scavenging antioxidant activity compared to other seaweeds. The study findings indicate that most of the studied metals in seaweeds exceeded the WHO-recommended levels. Aluminum was the highest (p < 0.05) accumulated metal in seaweeds compared to other metals. Toxic heavy metals, such as arsenic, cadmium and chromium, levels in all of the studied seaweeds surpassed the WHO limits. While seaweeds displayed acceptable nutritional and antioxidant properties, heavy metal presence poses a potential health risk to consumers. Products using seaweeds with accumulated heavy metals may have lower nutritional quality. Thus, this study underscores the need for comprehensive scientific investigation before developing high-quality natural food products or supplements from seaweeds.

Maximum entropy modelling to identify optimal locations for an IMTA system comprising Sparus aurata, Mytilus galloprovincialis and Ulva rigida on Europe’s Atlantic coastline

Meeting the resource demand for an increasing human population has led to the emergence of the aquaculture industry as the fastest growing sector for food production worldwide. Modern finfish aquaculture has raised environmental concerns and, to address this, Integrated Multi-Trophic Aquaculture (IMTA) has gained popularity as a means to minimise environmental impacts. This is done by culturing extractive species alongside fed species to utilise excess nutrients and enhance their own growth. The current study, based within the Atlantic Area of Europe, identified suitable habitats for the three species Sparus aurata, Mytilus galloprovincialis and Ulva rigida, for use in a new IMTA system. Models were created using MaxEnt software and input into GIS software (ArcMap 10.8.1) for analysis. For all species, the AUC results in the model were >0.9, with values of 0.931 (S. aurata), 0.928 (M. galloprovincialis) and 0.939 (U. rigida), demonstrating significant predictive power. Jackknife testing of the model for each species identified the mean sea surface temperature (°C) and Chlorophyll A (mg m–3) concentration as the two most important variables. The model showed that areas of >50% suitability could be found throughout the study area, although the most suitable sites were in coastal areas in more southern latitudes. To identify the feasibility of establishing an IMTA system in different areas, the shipping density, MPA status and the locations of harbours were added to the maps for further consideration. Using this study, and the species-specific information identified by the model, the aquaculture industry will be better equipped to identify potential IMTA sites and integrate these systems into the EU market for sustainable production.

Characterization of Proteins Extracted from Ulva sp., Padina sp., and Laurencia sp. Macroalgae Using Green Technology: Effect of In Vitro Digestion on Antioxidant and ACE-I Inhibitory Activity.

Macroalgal proteins were extracted from Ulva rigida (URPE) (green), Padina pavonica (PPPE) (brown), and Laurencia obtusa (LOPE) (red) using ultrasound-assisted enzymatic extraction, which is one of the green extraction technologies. Techno-functional, characteristic, and digestibility properties, and biological activities including antioxidant (AOA) and angiotensin-I converting enzyme (ACE-I) inhibitory activities were also investigated. According to the results, the extraction yield (EY) (94.74%) was detected in the extraction of L. obtusa, followed by U. rigida and P. pavonica. PPPE showed the highest ACE-I inhibitory activity before in vitro digestion. In contrast to PPPE, LOPE (20.90 ± 0.00%) and URPE (20.20 ± 0.00%) showed higher ACE-I inhibitory activity after in vitro digestion. The highest total phenolic content (TPC) (77.86 ± 1.00 mg GAE/g) was determined in LOPE. On the other hand, the highest AOACUPRAC (74.69 ± 1.78 mg TE/g) and AOAABTS (251.29 ± 5.0 mg TE/g) were detected in PPPE. After in vitro digestion, LOPE had the highest TPC (22.11 ± 2.18 mg GAE/g), AOACUPRAC (8.41 ± 0.06 mg TE/g), and AOAABTS (88.32 ± 0.65 mg TE/g) (p < 0.05). In vitro protein digestibility of three macroalgal protein extracts ranged from 84.35 ± 2.01% to 94.09 ± 0.00% (p < 0.05). Three macroalgae showed high oil holding capacity (OHC), especially PPPE (410.13 ± 16.37%) (p < 0.05), but they showed minimum foaming and emulsifying properties. The quality of the extracted macroalgal proteins was assessed using FTIR, SDS-PAGE, and DSC analyses. According to our findings, the method applied for macroalgal protein extraction could have a potential the promise of ultrasonication application as an environmentally friendly technology for food industry. Moreover, URPE, PPPE, and LOPE from sustainable sources may be attractive in terms of nourishment for people because of their digestibility, antioxidant properties, and ACE-I inhibitory activities.

Optimization of ultrasonic-assisted extraction of polysaccharides from Ulva rigida and evaluation of their antioxidant activity

Ultrasonic-assisted extraction (UAE) of sulfated polysaccharides from the cell walls of Ulva rigida green macroalgae was performed with a central composite design using the independent variables (pH 2–10, extraction temperature 40–80 °C, time 50–130 min and liquid/solid ratio of raw material 15–75 mL/g) with response surface methodology. Optimum conditions were obtained as pH 4.92, extraction temperature 73 °C, time 126 min, and the liquid/solid ratio of the raw material as 68 mL/g. Under these optimum conditions, the experimental yield was obtained as 13.22 %, and the results were close and in harmony with the estimated value of 12.91 %. FT-IR results, especially at the peaks corresponding to wave numbers 850 cm−1 and 1256 cm−1, the tension vibrations of sulfated esters in C-O-S and SO bonds were more clearly observed in the extracted ulvan components. As a result of the SEM images obtained by considering the surface morphology, it was observed that the sulfated polysaccharides from the cell wall were more prominently removed after the lipids were removed and as a result of the precipitation process. While the extracted sulfated polysaccharides showed higher antioxidant activity, although the results were close to each other. The total phenolic content was higher in the extracted sulfated polysaccharides.