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Marine natural resources are increasingly demanded to support the livelihoods and wellbeing of humans facing multiple and simultaneous crises across the planet. Seaweeds, in particular, are renowned sources of bioactive marine compounds used for various purposes, including human and animal nutrition, soil fertilization, and healthcare markets. DNA-based tools are being adopted in integrative taxonomy and ecological research, as well as to monitor the supply chain of commercially important species. This research provides novel insights into the population genetics, phylogenetic relationships, and haplotype network of six commercially significant seaweed species that are abundant in the Azores archipelago and currently traded for industrial applications. This study provides a detailed assessment of the genetic diversity of the red seaweeds Asparagopsis armata, Asparagopsis taxiformis, and Pterocladiella capillacea , and the brown seaweeds Halopteris scoparia, Zonaria tournefortii, and Cystoseira pustulata, contributing with 17 newly generated barcodes of COI, rbc L, and 28S rDNA gene records from the Azores region to the reference databases. Understanding the species identification and population dynamics is critical for understanding species composition in biodiversity hotspots. This knowledge supports taxonomy, conservation, environmental protection, and the sustainable use of marine resources. [Display omitted] • Population genetics, phylogenetic relationships, and haplotype networks of 6 traded Azorean seaweed species were presented. • 17 newly generated barcodes of marine macroalgae from the Azores archipelago were published. • New barcodes may further assist in the management of islands' biodiversity and natural resources' usage. • Three highly abundant seaweed species from the Azores were barcoded for the first time. • Molecular data from Azorean seaweeds will allow results to be compared between locations, across environments and over time. [ABSTRACT FROM AUTHOR]

The addition of macroalgae to livestock diets has demonstrated to enhance the quality of meat by improving the muscle stability, antioxidant capacity and fatty acid profile. However, information regarding rabbit meat is scarce. This study evaluated the effect of adding 1.025% of different macroalgae, dehydrated and as extracts (Saccharina latissima, Himanthalia elongata and Ulva spp.) to the diet of growing rabbits. Dietary supplementation with the Ulva spp. extract increased the fat content (0.96% vs 0.33% in control group) and the proportion of monounsaturated fatty acids (by 22%; P ≤ 0.022), but did not affect the moisture, protein or ash contents or the physicochemical properties of the rabbit longissiumus lumborum muscle. The antioxidant status of the meat was adequate and was not affected by the dietary supplements. The sensorial properties of the meat were also not affected, and dietary supplementation with both S. latissima and H. elongata actually enhanced the flavour and juiciness of the meat (P ≤ 0.01). Altogether, the study findings indicate that the addition of these sustainable ingredients to rabbit feed did not negatively affect meat quality, and some of them may potentially improve specific characteristics, which could make this meat more attractive to consumers. [ABSTRACT FROM AUTHOR]

Growing energy demand is inevitable in the future, due to increased commercialization and industrialization. Biohydrogen production from renewable biomass is considered as clean energy technology and, in this study, the feasibility of using Sargassum tennerimum as a renewable energy source has been attempted. Pretreatment using sonication pretreatment (ST) and surfactant Dioctyl sodium sulphosuccinate (DOSS) mediated ultrasonic pretreatment (DOSSSP) were investigated and the optimized pretreatment time and sonication power, respectively, were 30 and 200W for ST. DOSS dosage of 0.005 g/g TS was found to be optimum for DOSSSP with the corresponding maximum of 2600 mg/L and 27.36% respectively for sCOD (Soluble chemical oxygen demand) release and COD (Chemical oxygen demand) solubilization percentage. Biohydrogen assay analysis of the pretreated algal biomass was carried out and 86 mL/g COD of maximum biohydrogen production was achieved for DOSSSP pretreated sample than ST and control owing to higher COD solubilization percentage, carbohydrate and protein release. Energy analysis was performed to test the economic viability of the pretreatment process. This analysis showed that the maximum net positive energy of 0.0407 and energy ratio of 2.43 was obtained for DOSSSP revealing its economic viability. This study also reveals that macroalgae Sargassum tennerimum could be a sustainable renewable energy source for biohydrogen production as it is abundant throughout the year. [Display omitted] • Dioctyl sodium sulphosuccinate mediated ultrasonic pretreatment of macro algae for biohydrogen generation. • Biohydrogen production from macro algae, Sargassum tenerrimum under anaerobic conditions. • Maximum net energy outcome and higher energy ratio revealing most energy efficient pretreatment. • Sustainable macro algae source for profitable biohydrogen production. [ABSTRACT FROM AUTHOR]

Marine macroalgae (seaweeds) can accumulate high amounts of starch and cellulose in their tissues, hence, offering an attractive potential source of feedstock for bioethanol production. In this study we determined the specific growth rates (SGRs) in the seaweed Ulva sp. (Chlorophyta) during a full year cultured in a land-based facility to estimate sustainable biomass yields. We used 40 and 600 L outdoor tanks that received high and low irradiances, running seawater, aeration and external nutrients. Daily SGRs in 40 L tanks averaged 12 ± 2.04, 15.3 ± 0.8, 19.3 ± 1.8 and 10.3 ± 1.9% biomass increase per day for winter, spring, summer and autumn, respectively, while in 600 L growth averaged 2.5 ± 0.4, 2.2 ± 0.3, 9.8 ± 0.5 and 1.4 ± 0.4% d−1, respectively. In an up-scaled growth trial during summertime in larger culture units of 3400 and 27,000 L growth rates were 4.6 ± 0.8 and 8.7 ± 1.04% d−1, respectively. Altogether, the total biomass potential would yield 1.3 ton FW m−2 y−1. We also optimized enzymatic hydrolysis of dried biomass by means of time-course incubations with cellulase, amyloglucosidase and α-amylase in order to maximize the yields of total reducing sugars (TRS). We measured 163.6 ± 0.3, 179.7 ± 0.1 and 223.9 ± 0.5 mg TRS g−1 DW for summer, spring and winter months, respectively, with an average fermentation of the hydrolysate of 0.3 ± 0.06 g EtOH g−1 TRS. This work underlines the feasibility of seaweed feedstock production in land-based cultivation with respect to ethanol production. • Tank cultivation of the green seaweed Ulva sp. is sustainable year around. • Biomass yields are seasonal and ranged 1.5–5.2 kg FW m−2 y−1. • Hydrolyzed and fermented algal tissue yielded 0.3 ± 0.06 g of EtOH g−1 sugar. • Land-based seaweed facility could provide large biomass for bioethanol industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mixed Ulva intestinalis and Mimusops elengi oils for biodiesel production. • Optimization of reaction parameters through SPAT and RSM methods. • Simulation of process flow for industrial scale biodiesel production. • Project feasibility study through technoeconomic evaluation. • Minimum selling price of biodiesel was estimated to be 0.81 $/kg. • 0.088 kg CO 2 /kg of biodiesel emission estimated through carbon footprint analysis. The present research explored the sustainable production of biodiesel from mixed oils of marine macroalgae and non-edible seeds using a sulphonated Zinc doped recyclable biochar catalyst derived from coconut husk. The maximum biodiesel conversion of 94.8 % was yielded with optimized conditions of 10:1 methanol to oil molar ratio, 4.8 % biochar catalyst concentration, 54.5 ℃ temperature and 87.4 min reaction time. A techno-economic assessment provided a favourable return on investment (ROI) of 21.59 % and 4.63 years of reimbursement period, with a calculated minimum selling price of 0.81 $/kg of produced biodiesel. The carbon footprint analysis results estimated an annual emission of 752.07 t CO 2 which corresponds to 0.088 kg CO 2 emission per kg of biodiesel produced from the simulated process. The study on economic viability and environmental consciousness of biodiesel production not only paves the way for a greener and sustainable future while also contributing to low carbon footprint. [ABSTRACT FROM AUTHOR]

While seaweed cultivation has reached an advanced stage in many Asian countries, this industry remains nascent in Bangladesh, hindered by a lack of comprehensive site suitability mapping. To address this gap, we employed the Generalized Additive Model (GAM) approach to develop habitat suitability maps for different seaweed cultivation systems encompassing the entire coastal and marine territorial areas of Bangladesh. Our study leveraged an in-situ dataset comprising production and environmental factors from 180 cultivation plots of four species (Gracilaria sp., Enteromorpha intestinalis , Ulva lactuca , and Hypnea musciformis) across five cultivation sites, supplementing this data with other ecological variables derived from satellite observations and model simulations. The GAM analysis identified seven key explanatory variables that collectively accounted for 78 %, 76 %, and 79 % of the observed variability in seaweed data for off-bottom long-line, off-bottom net, and floating long-line cultivation systems, respectively. The model predicted that total suspended solids (TSS) predominantly influenced the habitat suitability for off-bottom net and floating long-line cultivation systems, while salinity was a crucial determinant for off-bottom long-line cultivation systems. The study further demonstrated that the predicted suitable areas (50–100 %) for floating long-line cultivation systems (1850 km2) substantially outnumbered those for off-bottom long-line (372 km2) and off-bottom net (380 km2) cultivation systems. The model showed that the southeast coast, specifically the sandy bottom areas of the Moheshkhali channel and its surroundings, exhibited high suitability (>75 % probability) for off-bottom long-line and off-bottom net cultivation systems. In contrast, the floating long-line cultivation system appeared most suitable for seaweed farming along almost the entire coastline of Bangladesh, excluding the Meghna and adjacent estuaries in the central region. Notably, the most suitable areas were specifically concentrated in the coastal areas of Moheshkhali Island, Cox's Bazar, Teknaf, and Saint Martin's Island in the southeast coastal zone, extending potentially to far offshore waters. The predictions of our model aligned well with in-situ observations, as evidenced by an area under the curve (AUC) of 0.83 and an R2 value of 0.85. The insights gleaned from this research offer invaluable guidance to seaweed farmers, entrepreneurs, and policymakers, thereby contributing to the sustainable development of the emerging seaweed-based blue economy in Bangladesh. • A habitat suitability map has been established using the Generalized Additive Model (GAM) • Effects of the ecological drivers on different culture system were evaluated • The estimated suitable area (50–100 %) for floating long-line culture systems greatly surpasses that of off-bottom systems • The floating long-line culture technique has been discovered to be the best option for seaweed farming • The southeast coast exhibited high suitability for off-bottom long-line and net culture systems [ABSTRACT FROM AUTHOR]

The present study investigates the algae-mediated synthesis, characterization, and H 2 O 2 sensing ability of silver nanoparticles using Sargassum spp. extract. The synthesized nanoparticles were spherical agglomerates and exhibited an absorbance peak at 418 nm, as analyzed by FE-SEM and UV–vis spectrophotometric analysis. TEM-SAED analysis interpreted the size between 2 and 35 nm and crystallinity corresponding to face-centered cubic (FCC) silver structure. This was further supported from XRD findings, which ascertained the presence of (111), (200), (220), and (311) lattice planes. FT-IR analysis confirmed the capping of algal phenolics as corresponding functional groups, which was further confirmed by XPS studies. The nanoparticles were observed to be highly stable in aqueous suspensions, due to the zeta potential value (−22.6 mV). On incubation of synthesized nanoparticles, with H 2 O 2 solutions, decolorization of nanoparticle solution was observed along with the reduction of absorbance peak at 418 nm. This color change could be utilized for H 2 O 2 detection in contaminated samples. Therefore, this study reveals the potential of sustainable Sargassum spp. biomass in synthesizing beneficial silver nanoparticles which could be exploited for environmental detection applications. [Display omitted] • AgNPs were synthesized using Sargassum spp. extract. • The AgNPs were observed to be highly stable zeta potential value (−22.6 mV). • Developed colorimetric method to detect H 2 O 2 in aqueous samples. [ABSTRACT FROM AUTHOR]

The present research focused on the extraction of algal oil from marine macroalgae Dictyota bartayresiana biomass, with the aim of optimizing the process using classical and statistical methods. The Soxhlet apparatus was used for the oil extraction and a design of experiments was developed to achieve the highest algal oil yield. Response surface methodology was used to determine the optimal conditions for the extraction process, which included a temperature of 80 °C, an extraction time of 120.40 min, solvent to biomass ratio of 4.74:1 (v:w), and a biomass moisture content of 6.36 %. The regression coefficient was determined to be of 0.97. The extraction kinetics was studied followed by the estimation of activation energy. The extracted algal oil was characterized using FT-IR and GC–MS, and a simulation of the extraction process was conducted for industrial scale production. A technoeconomic assessment was also performed, which revealed positive results with a 14.32 % return on investment, a payback period of 6.98 years, internal rate of return of 15.20 %, and net present value of 9,584,000 $. Overall, the study demonstrates the potential for sustainable extraction of algal oil from D. bartayresiana biomass for use in the production of biofuel. [Display omitted] • D. bartayresiana biomass was pre-treated for oil extraction. • The optimized highest oil yield of 8.86 % was achieved thorough RSM approach. • Characterization of the extracted oil studied through FT-IR and GC–MS • Profitability and sensitivity analysis of project using economic report • Payback period of 6.98 years with positive NPV of 9,584,000 $ [ABSTRACT FROM AUTHOR]

Marine macroalgae have attracted significant interest as a viable resource for biofuel and value-added chemical production due to their abundant availability, low production costs, and high carbohydrate and lipid content. The growing awareness of socio-economic factors worldwide has led to a greater consideration of marine macroalgae as a sustainable source for biofuel production and the generation of valuable products. The integration of biorefinery techniques into biofuel production processes holds immense potential for fostering the development of a circular bioeconomy on a broad scale. Extensive research was focused on the technoeconomic and environmental impact analysis of biofuel production from macroalgal biomass. The integrated biorefinery processes offers valuable pathways for the practical implementation of macroalgae in diverse conversion technologies. These studies provided crucial insights into the large-scale industrial production of biofuels and associated by-products. This review explores the utilization of marine macroalgal biomass for the production of biofuels and biochemicals. It examines the application of assessment tools for evaluating the sustainability of biorefinery processes, including process integration and optimization, life cycle assessment, techno-economic analysis, socio-economic analysis, and multi-criteria decision analysis. The review also discusses the limitations, bottlenecks, challenges, and future perspectives associated with utilizing macroalgal biomass for the production of biofuels and value-added chemicals. [Display omitted] • Macroalgae biorefinery for Sustainable biofuels and biochemicals production. • Integration of biorefinery techniques for circular bioeconomy and greener future. • Technoeconomic and environmental analysis of macroalgae biofuel production. • Assessment tools for sustainability of macroalgae biorefinery techniques. • Challenges and future perspectives in macroalgae based biofuels production. [ABSTRACT FROM AUTHOR]

This work presents an integrated approach for the extraction of lipids from marine macroalgae using RSM optimization and thermo-kinetic analysis. The lipids were extracted from marine macroalgal biomass using a Soxhlet extractor. The Soxhlet extraction parameters, including temperature (60–80 °C), solvent-to-algae ratio (3:1–7:1), algal particle size (0.05–0.25 mm), and extraction time (60–180 min), were optimized using RSM to achieve the maximum possible lipid extraction yield from marine macroalgae. The highest lipid extraction yield of 12.76% was obtained using the optimized conditions, which included an extraction temperature of 72 °C, a solvent-to-algae ratio of 5:1, an algal particle size of 0.16 mm, and an extraction time of 134 min. The kinetic analysis revealed an activation energy of 52.79 kJ mol−1 for the Soxhlet extraction process. The thermodynamic analysis of the Soxhlet extraction process demonstrated the following results: ΔH = 49.98 kJ mol−1, ΔS = −128.24 J K−1 mol−1, and ΔG = 93.98 kJ mol−1. The GC-MS analysis confirmed that the extracted algal lipids exhibited a composition of 14.20% palmitic acid, 4.89% stearic acid, and 76.97% oleic acid. The physiochemical analysis ensured that the extracted algal lipids possess excellent qualities, making them desirable for sustainable biofuel production. [Display omitted] • The lipids from the marine macroalgae were extracted using a Soxhlet extractor. • Optimization of extraction parameters via RSM enhanced the lipid yield to 12.76%. • The kinetic analysis revealed an E a of 52.79 kJ mol−1 for the Soxhlet extraction. • ΔH = 49.98 kJ mol−1, ΔS = −128.24 J K−1mol−1, and ΔG = 93.98 kJ mol−1 were obtained. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Bridging nutritional, physicochemical, and sensory attributes of seaweeds • Taste pattern: very salty, medium umami, a little bitter and sour, and not sweet • PP displays sea and shellfish odour, umami taste, and hard and chewy texture • UL was salty, with lemon and fresh grass odour, and neither crispy, hard nor chewy • SL and AE resemble each other in saltiness, sea flavour and texture [ABSTRACT FROM AUTHOR]

Macroalgae are unavoidable biological elements when monitoring and assessing costal environments. However, these tasks can be difficult to address because macroalgae a) present a high natural variability across a range of spatial and temporal scales, b) they imply a high sampling and laboratory processing effort and good taxonomical expertise (as they are a very diverse group of species), and c) there is insufficient knowledge about their structural and functional characteristics. This work addressed how the vertical (intertidal zonation) and horizontal (latitudinal gradient) variability of macroalgae assemblages are structured across continental Portugal, as well as how some surrogates for species-level biodiversity measures (namely functional groups and thallus morphology approaches) respond to such large-scale variability. Particularly, it was tested if intertidal zonation patterns are higher than fine-scale horizontal variation, and however, if vertical variation decreases along broad-scale horizontal variation. To do so, cover per species was taken (using a photographical and GIS methodological approach) from five sites located along the shoreline and along respective upper- mid- and lower-intertidal zones. The work findings include that both intertidal and latitudinal gradients impose deep structural changes on assemblages patterns. That is, broad-scale processes along Portuguese latitudes act as strongly as vertical stress gradients on assemblages patterns. Functional groups and thallus morphology approaches were useful to generalize the latitudinal assemblages patterns, where some groups emerge at the expense of others, and may improve biodiversity understanding and ecological synthesis. Because these surrogates decrease taxonomical expertise needs and can provide insight into the functional structure of macroalgal communities, their patterns founded may be particularly useful as reference data for further monitoring, so that shifts in such patterns might represent early warning surrogate approaches to detect environmental impact changes. Ultimately, to generate broader databases on rocky shore assemblages diversity (from species-level to functional groups and thallus morphologies approaches) can be useful for large-scale comparisons and for establishing ecological reference conditions, including for monitoring programs and environmental impact studies. [ABSTRACT FROM AUTHOR]

In-depth metabolic profiling, also termed metabolomics, provides detailed information about the biochemical phenotype of an organism. Besides improving our understanding of biochemical processes, metabolomics is used for environmental monitoring, natural product discovery, or even chemotaxonomy, among others. However, for marine macroalgae, comparative large-scale metabolomics studies are lacking, even though seaweeds belong to the most important aquatic primary producers. In this study, we present via a broad scale systematic metabolomics survey 391 metabolites from 21 seaweeds species, representing brown, red and green algae. We demonstrate clear differences in metabolite composition of these seaweeds, reflecting their taxonomic classification. We highlight these differences for amino acid, amino acid derivative and peptide metabolites, energy and carbohydrate metabolites, for lipid, fatty acid and sterol metabolites and for secondary metabolites, including selected metabolic pathways such as the urea cycle, the citrate cycle and the glyconeogenesis/glycolysis, besides others. Additionally, we link selected seaweed biochemical properties to potential pharmaceutical and nutraceutical applications. [ABSTRACT FROM AUTHOR]

The main objective of this study was to obtain guidelines for the hydrothermal pretreatment of kelp for the isolation of uronic acids. This was done by determining the effect of hydrothermal treatment on the kinetic of the decomposition of mannuronic acid (MA) and guluronic acid (GA). These uronic acids were obtained by the hydrolysis of alginic acid originating from kelp. Each uronic acid was treated under hydrothermal conditions using a continuous-flow reactor. The temperature ranged from 170 to 250 °C, the residence time was varied between 5 and 100 s, and the pressure was set at 25 MPa. The decomposed products were analyzed with high-performance liquid chromatography (HPLC). The yields of both uronic acids showed similar trends; they decreased as the temperature was increased. Activation energies for the decomposition of MA and GA were approximately 28.3 and 20.6 kJ/mol, respectively, and pre-exponential factors were determined to be 282 and 40.6 s −1 , respectively. Uronic acids were readily decomposed under hydrothermal conditions. Calculations showed the superiority of the continuous reactor over the autoclave reactor, in terms of the recovery of uronic acids. [ABSTRACT FROM AUTHOR]

Results of 7-days exposure to metals, using environmentally realistic conditions, evidenced the high potential of living Fucus vesiculosus to remove Pb, Hg and Cd from contaminated salt waters. For different contamination scenarios (single- and multi-contamination), ca 450 mg L −1 (dry weight), enable to reduce the concentrations of Pb in 65%, of Hg in 95% and of Cd between 25 and 76%. Overall, bioconcentration factors ranged from 600 to 2300. Elovich kinetic model described very well the bioaccumulation of Pb and Cd over time, while pseudo-second-order model adjusted better to experimental data regarding Hg. F. vesiculosus showed different affinity toward studied metals, following the sequence order: Hg > Pb > Cd. Analysis of metal content in the macroalgae after bioaccumulation, proved that all metal removed from solution was bound to the biomass. Depuration experiments reveled no significant loss of metal back to solution. Exposure to contaminants only adversely affected the organism's growth for the highest concentrations of Cd and Pb. Findings are an important contribute for the development of remediation biotechnologies for confined saline waters contaminated with trace metal contaminants, more efficient and with lower costs than the traditional treatment methods. [ABSTRACT FROM AUTHOR]

Samples of dried marine macroalgae ( Fucus serratus , Palmaria palmata and Ulva lactuca ) have been analysed for trace elements by a novel, non-destructive approach involving a Niton field-portable-X-ray fluorescence (FP-XRF) spectrometer configured in a low density plastics mode with thickness correction. Detection limits for a 200-s counting time ranged from <5 μg g −1 for As and Pb in F. serratus and As in P. palmata to several tens of μg g −1 for Cd, Sb and Sn in all species tested. Arsenic, Cu, Pb and Zn were detected by the XRF in samples collected from a protected beach ( n = 18) and in samples therefrom that had been exposed to additional aqueous elements in combination ( n = 72) with concentrations returned (in μg g −1 ) ranging from 3.9 to 39.7 for As, 13.0 to 307 for Cu, 6.1 to 14.7 for Pb and 12.5 to 522 for Zn. Independent measurements of trace elements in the macroalgae by ICP-MS following nitric acid digestion revealed a direct and significant proportionality with concentrations returned by the XRF, with slopes of the XRF-ICP relationships (As = 1.0; Cu = 2.3; Pb = 2.4; Zn = 1.7) that can be used to calibrate the instrument for direct measurements. The approach shows potential for the in situ monitoring of macroalgae in coastal regions that is currently being investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biodiesel production from marine macroalgae Dictyota bartayresiana oil was studied. • CaO nanocatalyst was synthesized using waste collected from building demolition site. • The reaction parameters for efficient production of biodiesel was optimized. • Investigation on techno-economic aspects was studied for biodiesel production. • Sensitivity analysis was used to study the uncertainty of biodiesel production process. The investigation on utilizing macroalgae for industrial scale biodiesel production is an imperative action needed for commercialization. In the present research work, the biooil from marine macroalgae Dictyota bartayresiana was used for biodiesel production using calcium oxide nanocatalyst synthesized using waste collected from building demolition site. The optimization results obtained were the calcination temperature 573 °C, concentration of catalyst 5.62%, methanol to oil molar ratio 14.36:1, temperature 55.7 °C and time 67.57 min for the transesterification with the biodiesel yield of 89.6%. The techno-economic aspects of biodiesel production were investigated for 20 MT/batch. The return on investment and internal rate of return from the biodiesel production plant was found to be 25.39% and 31.13% respectively. The plant payback period was about 3.94 years with a positive NPV value of about 14,053,000 $/yr. Thus, Dictyota bartayresiana biomass can be efficiently used for the sustainable production of biodiesel. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis and activation of biochar derived catalyst is critically examined. • Activation of biochar catalyst has significant impact for biofuel production. • Challenge and way forward is presented by highlighting research gaps. Biodiesel is considered as a promising sustainable biofuel from renewable resources with lower pollutant emissions. However, high production cost, difficulty in recovering catalyst, and an expensive separation process associated with the use of homogeneous catalysts are still critical challenges. Heterogeneous catalysts derived from biomass are considered as viable options. Marine macroalgae-derived biochar owing to its vast surface area, diverse functional groups, presence of inorganics, and high porosity, could be considered as a suitable heterogeneous catalyst or as a supported catalyst for biodiesel synthesis. Thermochemical conversion processes, such as hydrothermal carbonization and pyrolysis, convert marine macroalgae biomass into biochar, which primarily composed of carbon, oxygen, and inorganics (Ca, K, Mg, Fe, etc.). The activation of macroalgae-derived biochar either physically or chemically played a vital role towards biofuel production. The catalytic activity and the performance of the macroalgae-derived biochar catalyst are influenced by its physicochemical properties (–SO 3 H group density, porosity, overall surface area, functional groups, and so on). Biodiesel production over marine macroalgae-derived biochar catalyst represents a more sustainable solution to current energy demands and develops economically beneficial biodiesel technology. This article provides a critical assessment of the marine macroalgae-derived biochar catalysts for the production of biodiesel. Initially, macroalgal biochar is produced through different thermochemical conversion technologies, including hydrothermal carbonization and pyrolysis, and its yield and physicochemical characteristics are discussed. After that, various techniques for the activation of macroalgae-derived biochar are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ulva sp. was explored to remediate a complex mixture made of 13 elements mimicking an effluent. • Kinetics followed Elovich model for all elements, except Hg, Cu, Y and Ce. • Hierarchical Cluster Analysis confirmed the similar behaviour of REEs in aqueous solutions. • Cu, Zn, Cd, Pb, Y, La, Eu, Gd, Tb were retained in the surface, while Hg was most accumulated. • SEM analysis revealed a clean surface after EDTA washing procedure. Hazardous leachate/effluent from fluorescent lamps contains potentially toxic elements such as Hg and Pb, and critical raw materials such as rare earth elements (REEs). This work evaluated the ability of the live macroalgae Ulva sp. to remediate a simulated lamp industry wastewater consisting of a complex mixture of elements (Y, Eu, La, Ce, Tb, Gd, Hg, Pb, Zn, Cu, Co, Cd, and Pt), with particular emphasis on the investigation of the sorption mechanisms. Experiments were performed with 3.0 g/L (fresh weight) of Ulva sp., salinity 25, and an initial concentration of 100 µg/L for each element. Hierarchical cluster analysis highlighted two main groups according to removal: Pt and Cd as the less removed, and all others with removals > 76 %, underlining Hg and Ce with the fastest kinetics (up to 92 %). Apart from Co, Zn and Cd, all mathematical models described sorption kinetics well, with Akaike Information Criteria identifying the Elovich model as the best for describing REEs sorption. FTIR analysis identified the sulphated polysaccharide Ulvan as intervening in binding elements to Ulva biomass. Extraction with EDTA 0.001 mol/L showed that most elements were mainly localized in the outer fraction (surface), except for Hg, which was entirely in the inner part. SEM analysis supported the EDTA analysis and showed a clean surface after washing. The results are an important contribution to the understanding of sorption mechanisms in macroalgae and demonstrate the feasibility of macroalgae-based biotechnologies with reduced costs and high efficiency for water decontamination, in complex saline mixtures. [ABSTRACT FROM AUTHOR]

In this work, granular biochar, Laminaria japonica -derived biochar (LB)-calcium alginate beads (LB-CAB), was successfully prepared by dropping a mixture of powder biochar and alginate solution into a calcium chloride solution for phosphate adsorption. Among different marine macroalgae derived biochars, LB exhibited the best performance, showing a phosphate removal rate of 97.02%, which was attributed to its high Ca/P and Mg/P ratios. With increasing pyrolysis temperature up to 600 °C, the physicochemical properties of LB became suitable for adsorbing phosphate. Experimental results of kinetics and equilibrium isotherms at different temperatures (10–30 °C) showed that the phosphate adsorption process is endothermic and is mainly controlled by external mass transfer and the intraparticle diffusion rate. The maximum adsorption capacity was found to be 157.7 mg g −1 at 30 °C, as fitted by the Langmuir–Freundlich model, which is higher than capacities of other powder form of biochars. [ABSTRACT FROM AUTHOR]

A novel combined electrochemical modification (CEM) method, using a graphite electrode-based electric field and MgCl 2 as electrolyte, was newly developed to prepare porosity-enhanced biochar containing periclase (MgO) nanocomposites (PE-MgO/biochar). During the CEM method, the dried marine macroalgae was immersed in the MgCl 2 solution, and a voltage of 20 V was then applied for 10 min prior to pyrolysis. Morphological and chemical analyses results showed that nano-sized MgO particles with a highly crystalline structure were dispersed and enriched on the surface of the PE-MgO/biochar, which enabled higher phosphate adsorption capability. In an adsorption equilibrium test, among various biochars, PE-MgO/biochar exhibited the highest phosphate adsorption capacity from aqueous solution with a Langmuir–Freundlich maximum adsorption capacity as high as 620 mg-P g −1 . It can be concluded that the newly introduced CEM method is a potent additional technique to effectively prepare modified-biochar in terms of a simple and time-saving modification method. [ABSTRACT FROM AUTHOR]

The collected roots of Undaria pinnatifida , the main waste in farming sites, accounting for 40–60% of annual production, was pyrolyzed under temperature ranging from 200 to 800 °C to evaluate the influence of pyrolysis temperature on biochar properties and phosphate adsorption capacity. It was confirmed that an increase in the pyrolysis temperature led to a decrease of the yield of biochar, while ash content remained almost due to carbonization followed by mineralization. Elemental analysis results indicated an increase in aromaticity and decreased polarity at a high pyrolysis temperature. When the pyrolysis temperature was increased up to 400 °C, the phosphate adsorption capacity was enhanced, while a further increase in the pyrolysis temperature lowered the adsorption capacity due to blocked pores in the biochar during pyrolysis. Finally, a pot experiment revealed that biochar derived from waste-marine macroalgae is a potent and eco-friendly alternative material for fertilizer after phosphate adsorption. [ABSTRACT FROM AUTHOR]

A meta-analysis was performed to examine the dietary inclusion of marine macroalgae species to target methane (CH 4) reduction from ruminant animals and the effects on rumen fermentation and animal performance. A literature search was conducted from global scientific databases, resulting in 25 in vitro and 22 in vivo studies eligible to be integrated in a database. A total of 673 experimental units comprising 537 in vitro and 136 in vivo experimental units were analyzed by using mixed model methodology in SAS and multivariate analysis in R Studio. Principal component analysis (PCA) from in vitro dataset revealed difference effects of brown, green, and red macroalgae on CH 4 production without a pronounced pattern on rumen fermentation. Likewise, PCA from in vivo dataset supported the in vitro results whereas Ascophyllum nodosum (brown) and Asparagopsis taxiformis (A. taxiformis ; red) species showed noticeably separated clusters on CH 4 production. Mixed regression analysis from in vitro and in vivo databases showed interaction effects (P < 0.001) between levels × species on CH 4 production and the percentages of acetate (C 2), propionate (C 3), butyrate (C 4) whereas A. taxiformis showed the greatest effects on the decrease of C 2 and increase of C 3 proportions (P < 0.001), among other species. Additionally, dietary levels of A. taxiformis had strong linear decrease (R 2 = 0.946 ; P < 0.001) on CH 4 (g/d) and curvilinear effect on CH 4 when expressed as g/kg DMI (R 2 = 0.687 ; P < 0.001). When considering the types of animals, A. taxiformis decreased (P < 0.001) CH 4 by 64.76 % in beef cattle but the effect in dairy cows and small ruminant were non-significant (P > 0.05) compared with control diet as a reference. Curvilinear effect on in vitro organic matter digestibility (P = 0.043) and linear degreased on crude protein digestibility (P = 0.029) were found. Feeding macroalgae did not affect dry matter intake (DMI), average daily gain (ADG), milk production and milk composition except for milk lactose which linearly increased (R 2 = 0.731 ; P = 0.002) by increasing Ascophyllum nodosum level. In dairy cows, the inclusion of A. taxiformis increased iodine concentration by more than six-fold increase (P < 0.001) while other species had no substantial effect on iodine concentration. Taken together, macroalgae can be used as feed ingredients for ruminants to decrease CH 4 emissions without detrimental effects on metabolism and production performance in ruminant livestock. Notwithstanding, feeding A. taxiformis > 10 g/kg DM of diet may result in an unfavorable effect on the high bromoform and iodine residuals in milk. Future in vivo study using less-explored species that had been tested in vitro need to be conducted. [Display omitted] • Meta-analysis was performed with 25 in vitro and 22 in vivo macroalgae studies in ruminant. • A. taxiformis had strongest linear effect on CH 4 reduction (g/d). • A. taxiformis decreased acetate and increased propionate proportions in rumen. • In beef cattle, A. taxiformis decreased CH 4 by 64.76 % compared with control diet. • Macroalgae did not affect dry matter intake and ruminant's production. [ABSTRACT FROM AUTHOR]

This study aimed to assess and explore the bioaccumulation capabilities of three different macroalgae species, Ulva lactuca (green), Gracilaria gracilis (red) and Fucus vesiculosus (brown), very common on temperate coasts and estuaries, for the removal of mercury (Hg) from contaminated waters (with high salinity), using environmentally realistic concentrations of metal (10–100 μg L −1 ). Levels of Hg accumulated by all seaweeds ranged between 20.8 and 208 μg g −1 , corresponding to bioconcentration factors of c.a. 2000. A comparative evaluation of bioaccumulation (living biomass) and biosorption (dried biomass) was performed for U. lactuca , which had displayed the best performance in accumulating Hg. The removal conducted by the living seaweed ( m macroalgae / V solution ≈ 500 mg L −1 ), although slower, was more promising since all Hg levels were reduced by about 99%, fulfilling the European criteria for drinking water quality. Pseudo-second-order and Elovich models described quite well the experimental data, assuming a process essentially of chemical nature. Determination of total Hg content in algal biomass over time, allowed to confirm and to follow the uptake of this metal by the living organism. Volatilization of Hg or its conversion to organo-metallic forms (0.02–0.05%) was negligible during the decontamination process. Overall, the results are a contribution for the development of an efficient and cost-effective water remediation biotechnology, based on the use of living macroalgae to promote the removal of Hg. [ABSTRACT FROM AUTHOR]

Various marine sediments were evaluated as promising microbial sources for methane fermentation of Saccharina japonica , a brown alga, at seawater salinity. All marine sediments tested produced mainly acetate among volatile fatty acids. One marine sediment completely converted the produced volatile fatty acids to methane in a short period. Archaeal community analysis revealed that acetoclastic methanogens belonging to the Methanosarcina genus dominated after cultivation. Measurement of the specific conversion rate at each step of methane production under saline conditions demonstrated that the marine sediments had higher conversion rates of butyrate and acetate than mesophilic methanogenic granules. These results clearly show that marine sediments can be used as microbial sources for methane production from algae under high-salt conditions without dilution. [ABSTRACT FROM AUTHOR]

Highlights: [•] Caulerpa peltata is a renewable feedstock, which has been used for first time. [•] Maximum yield of ME 98.11% was achieved by acid–base catalyzed transesterification. [•] Characterization of biodiesel was performed by spectroscopy analysis. [•] Fuel properties of algal biodiesel were satisfied ASTM standards limits. [•] Acid–base transesterification was an efficient method for C. peltata algal oil biomass. [Copyright &y& Elsevier]

Marine macroalgal biomass provides polysaccharides that could result in the valuable transformation of waste into an economic resource. Crude extracts, or polysaccharides, from Chaetomorpha aerea (Chlorophyta) and Agardhiella subulata and Hypnea cornuta (Rhodophyta), collected from the coastal brackish Lake Ganzirri (Italy), were evaluated for their effects on the adhesion and biofilm formation of Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213, as model organisms. Without exerting any antibacterial activity, each crude extract showed dose-dependent inhibitory effect on biofilm formation, differing each other and also on the strain tested. The highest concentration (400 μg mL−1) of C. aerea extract, a sulfated polysaccharide mainly composed by glucuronic acid, strongly acted on the initial attachment of P. aeruginosa (54% of biofilm reduction), whereas H. cornuta extract greatly acted on that of S. aureus (59%). The addition of A. subulata and C. aerea extracts reduced the biofilm growth of S. aureus , but did not its mature biofilm. Conversely, A. subulata extract, a κ-carrageenan was also able to reduce the developed biofilm of P. aeruginosa. As resulted by surface-coating and the bacterial affinity to hydrocarbons assays, extracts from C. aerea and H. cornuta were able to inhibit the adhesion to polystyrene of P. aeruginosa and S. aureus, and modify their cell-surface properties and hydrophobicity. Furthermore, all the extracts formed stable emulsions. No in vitro cytotoxicity effects were observed for H. cornuta extract, while they were moderate for C. aerea and high for A. subulata. However, all the extracts did not show any potential toxicity in vivo fish-embryo Danio rerio assay. These extracts could be used to prevent or remove the bacterial biofilms in several medical and non-medical applications. • Seaweed biomass provides polysaccharides able to hinder bacterial biofilm formation. • C. aerea and H. cornuta extracts strongly acted on the initial bacterial attachment. • A. subulata extract was able to reduce the developed biofilm of P. aeruginosa. • No in vivo toxicity effects of crude polysaccharides were observed in D. rerio assay. [ABSTRACT FROM AUTHOR]

Highlights: [•] Presentation of a laboratory experiment for analysis of reflectance spectra of marine macroalgae. [•] At the higher taxonomic group level, spectral mixture of macroalgae is linear. [•] Inner-group spectral similarity is high; therefore unmixing can hardly be performed. [•] Sub-pixel analysis of macroalgae is feasible to a limited extend. [Copyright &y& Elsevier]

Abstract: In this investigation, Enteromorpha compressa algal oil with high free fatty acids (FFA) used as a feedstock for biodiesel production. Two step process was developed and kinetic study executed to obtain reaction rate constant for the transesterification reaction. The acid esterification was carried out to reduce FFA from 6.3% to 0.34% with optimized parameters of 1.5% H2SO4, 12:1 methanol–oil ratio, 400rpm at 60°C and 90min of reaction time. The maximum biodiesel yield 90.6% was achieved from base transesterification through optimum conditions of 1% NaOH, 9:1 methanol–oil ratio, 600rpm and 60°C temperature for 70min. The algal biodiesel was characterized by GC–MS, HPLC and NIR. This transesterification follows first order reaction kinetics and the activation energy was determined as 73,154.89J/mol. The biodiesel properties were analyzed and found to be within the limits of American standards. Hence, E. compressa serves as a valuable renewable raw-material for biodiesel production. [Copyright &y& Elsevier]

Abstract: The Water Framework Directive (WFD) requires European Member States to assess the Ecological Quality Status (EQS) of their water bodies based on Biological Quality Elements (BQEs). A tool called MarMAT (Marine Macroalgae Assessment Tool) was developed to implement the WFD in Portugal, which assesses the EQS of Portugal''s coastal intertidal rocky shores. MarMAT is a multimetric method that is compliant with the European WFD requirement. It is based on the composition (Chlorophyta, Phaeophyceae and Rhodophyta) and abundance (coverage of opportunists) of marine macroalgae. This study focused on the demands of the WFD to have the assessment methodologies legally accepted by the European Commission. The following factors were examined: (a) the response of MarMAT against anthropogenic pressures; (b) the ability of MarMAT to report all of the five quality classes (bad, poor, moderate, good and high); and (c) the performance of MarMAT, specifically in comparing the RSL (Reduced Species List) methodology with the utility of including the abundance (coverage of opportunists) metric and the necessity of locally adapted reference conditions and boundaries. MarMAT was high inversely correlated (p <0.001) with anthropogenic pressure. MarMAT also successfully reported all of the quality classes (bad to high) and captured the community changes more accurately when using the coverage of opportunists metric. Because MarMAT satisfactorily covered all of the issues examined, MarMAT may be accepted as a compliant assessment methodology in the scope of the WFD requirements. [Copyright &y& Elsevier]

Abstract: Macroalgae build biogenic habitats which give shelter and provide a suitable physical environment for a great variety of organisms. Structural complexity of algal substrates may influence the composition of their attached epifauna. The aim of this study is to test whether the taxonomic relatedness of the algal hosts and the functional groups to which they belong influence the species richness and composition of their epifaunal bryozoans. We analysed 36 algal genera from the Atlantic coast of South America between 42°S and Cape Horn. Changes in bryozoan species richness (number of species) among different algal functional groups (filamentous algae, foliose algae, corticated foliose algae, corticated macrophytes) were non-significant. The composition of the epifaunal assemblages differed significantly only between filamentous and foliose algae. Sheet-like bryozoans (i.e. encrusting, pluriserial colonies) were more frequent on foliose than on filamentous algae, while runner-like species (i.e. uniserial stolons) were characteristic epibionts on filamentous thallii. Similarity of bryozoan assemblages increased with increasing taxonomic relatedness of their hosts. As most filamentous seaweeds analysed in this study are members of the Order Ceramiales, the influence of algal taxonomic relatedness and functional groups on the composition of their bryozoan assemblages can be viewed as two different aspects of the same phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: A two-dimensional biomarker approach, using stable isotopes (δ13C, δ15N) and fatty acids, was used to evaluate differences both amongst and within benthic primary producer types (seagrass, fleshy red algae, calcareous red algae, brown algae, and seagrass periphyton) that are typical of the nearshore, temperate Australian region. The primary source of variance (as examined by permutational ANOVA) for all biomarkers examined was amongst primary producer types, as opposed to amongst species within type. δ13C showed a clear separation (Monte Carlo p <0.05) between seagrass (range of means=−10.1 to −14.0‰) and macroalgae (−14.6 to −25.2‰), but could not differentiate amongst the algal types examined. Similarly, distinct δ15N signatures (p <0.05) were found only for seagrass (range of means=3.6–4.1‰) versus calcareous red algae (4.6–5.5‰), with all other types overlapping in their mean δ15N values. In contrast, multivariate analysis of fatty acid data (using Canonical Analysis of Principal coordinates; CAP) distinguished not only between seagrass and macroalgae, but also between red and brown algae (and to a limited extent between the calcareous and fleshy red algal types). The principal unsaturated fatty acids in the samples were C20 polyunsaturates (found primarily in the macroalgae and periphyton), and C18 mono- and polyunsaturates, with high proportions of 18:2n-6 and 18:3n-3 typical of the seagrasses. The C18 monounsaturate 18:1n-7 was one of the most diagnostic compounds for the red algae examined, being present in very low amounts in seagrass and virtually absent in the brown algae. Conversely, brown algae were high in 18:4n-3, with 20:4n-3 particularly diagnostic of the kelp Ecklonia radiata. In contrast to stable isotopes, fatty acids helped distinguish different algal groups, thereby providing support that a two-dimensional approach using stable isotopes and fatty acids is likely to provide the most useful tool to distinguish primary producers in food web structure. [Copyright &y& Elsevier]

Abstract: This work reports the results of the study for cadmium binding by the dead red macroalga Mastocarpus stellatus. Kinetics sorption experiments demonstrated the high rate of metal biosorption: the system attained over 50% of the total biomass cadmium uptake within 2min of contact and over 90% in the first 9min. The kinetic data were successfully described by a pseudo-second order model with rate constants ranging from 1.06 to 10gmmol−1 min−1, as a function of initial metal concentration and temperature. The equilibrium binding was accurately represented in terms of Langmuir and Langmuir–Freundlich models. The sorption isotherms at constant pH showed uptake values as 0.49mmolg−1 (at pH 2.4), 0.56mmolg−1 (at pH 4) and 0.59mmolg−1 (at pH 6), while the affinity constant values were between 0.6 and 5mmol−1 L (Langmuir fit). The acid–base properties of the alga were also studied, obtaining the total number of acid groups, 2.5mmolg−1, and their apparent pK value, 1.56, using the Katchalsky model. Desorption studies were conducted employing different HNO3 concentrations and desorption times. [Copyright &y& Elsevier]

Axenic plantlets derived from three species of marine macroalgae, the temperate green alga Acrosiphonia coalita, the temperate red alga Porphyra yezoensis, and the tropical red alga Portieria hornemannii, all possessed a similar metabolic route to remove the explosive compound 2,4,6-trinitrotolune (TNT) from seawater. At a biomass density of 1.2gl−1 and initial TNT concentrations of 10mgl−1 or less, TNT removal from seawater was 100% within 72h for P. hornemannii and P. yezoensis. Specific rate constants for TNT uptake were 0.016–0.018lg−1 FWh−1 for A. coalita filaments, 0.047–0.062lg−1 FWh−1 for P. yezoensis blades, and 0.037–0.049lg−1 FWh−1 for P. hornemannii microplantlets. Only trace amounts of TNT were found within the biomass. All species reduced TNT to 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dintrotoluene, but these products never accounted for more than 20% of the initial TNT. [Copyright &y& Elsevier]

Abstract: Levels of radionuclides in seven species of marine brown algae and Ulva were determined to establish a baseline for the Northern Pacific Ocean/Bering Sea (Aleutian Islands). There were differences in levels among algal species and locations (Amchitka Island vs Kiska Island). No values were above the minimum detectable activity (MDA) level for 137Cs, 129I, 60Co, 152Eu, 90Sr, and 99Tc. There were interspecific differences in some radionuclides: Ulva lactuca (=Ulva fenestrata) had the highest levels of 241Am, Alaria fistulosa had the highest levels of 239,240Pu, and Fucus distichus (=Fucus gardneri) had the highest levels of 234U, 235U, and 238U. However, levels of all radionuclides were generally low and near the MDA for all isotopes. Although Amchitka Island had higher levels of 239,240Pu than Kiska, the differences were very small and not significant biologically. The data indicate that algae can be useful bioindicators of actinides because they accumulate them at very low environmental levels, allowing them to provide early warning of any potential seepage of radionuclides into the marine environment. Further, the data indicate that some species (the intertidal Fucus) are better accumulators than others, and these should be used as bioindicators in future monitoring schemes. [Copyright &y& Elsevier]

Abstract: This work reports kinetic and equilibrium studies of cadmium(II) and lead(II) adsorption by the brown seaweed Cystoseira baccata. Kinetic experiments demonstrated rapid metal uptake. Kinetic data were satisfactorily described by a pseudo-second order chemical sorption process. Temperature change from 15 to 45°C showed small variation on kinetic parameters. Langmuir–Freundlich equation was selected to describe the metal isotherms and the proton binding in acid–base titrations. The maximum metal uptake values were around 0.9mmolg−1 (101 and 186mgg−1 for cadmium(II) and lead(II), respectively) at pH 4.5 (raw biomass), while the number of weak acid groups were 2.2mmolg−1 and their proton binding constant, K H, 103.67 (protonated biomass). FTIR analysis confirmed the participation of carboxyl groups in metal uptake. The metal sorption was found to increase with the solution pH reaching a plateau above pH 4. Calcium and sodium nitrate salts in solution were found to affect considerably the metal biosorption. [Copyright &y& Elsevier]

Abstract: Five different brown seaweeds, Bifurcaria bifurcata, Saccorhiza polyschides, Ascophyllum nodosum, Laminaria ochroleuca and Pelvetia caniculata were studied for their ability to remove cadmium from aqueous solution. Kinetics of cadmium adsorption by all the algae were relatively fast, with 90% of total adsorption occurring in less than 1h. These experiments could be accurately described by a pseudo-second-order rate equation, obtaining values between 1.66×10−3 and 9.92×10−3 g/mgmin for the sorption rate constant k. Several equilibrium adsorption isotherms were obtained for the quantitative description of cadmium uptake. The use of the Langmuir isotherm led to values between 64 and 95mg/g for q max and between 0.036 and 0.094L/mg for b. The effect of pH on biosorption was also studied. Acid–base properties of algae were studied by potentiometry to determine pK values (from 3.54 to 3.98) and the total number of acid groups. [Copyright &y& Elsevier]

In this study, we determined the antioxidative potential of 15 marine macroalgae by measuring the photosynthetic efficiency under artificial oxidative stress after a 30-min exposure to a series of ascending H2O2 concentrations. Species exhibiting high maximum quantum yields (Fv/Fm values) were regarded as not susceptible towards H2O2 stress. In addition to the short-term stress experiments, the antioxidative defense systems (enzymatic and non-enzymatic) of selected algal species under longer exposure times to H2O2 were investigated.Species with striking photosynthetic activity under H2O2 stress were Chaetomorpha melagonium (Chlorophyta), showing 40% reduced Fv/Fm as compared to the control after 8 days of exposure to 20 mM H2O2. In Fucus distichus (Phaeophyta) Fv/Fm decreased to 50% of the control under the same exposure conditions. Polysiphonia arctica (Rhodophyta) exhibited highest Fv/Fm values with a reduction of only 25%, therefore possessing the highest antioxidative potential of the investigated species.In P. arctica the activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), as well as the pool size of the antioxidant ascorbic acid were investigated. When exposed to different H2O2 concentrations (0–2 mM) over 6 days, the intrinsic activities of SOD and GR were stimulated. In a kinetic study over 8 days, the activity of antioxidative enzymes APX and CAT as well as ascorbic acid content were recorded. APX activity was much higher in H2O2-treated thalli at the end of the experiment than in the control, also CAT activity increased significantly with increasing H2O2 stress. In parallel, ascorbic acid content was reduced under high H2O2 concentrations. Furthermore, by using GC–MS techniques in P. arctica bromophenolic compounds with antioxidative properties were identified.This study shows that the measurement of the in vivo fluorescence of photosystem II is a suitable tool to determine the effect of oxidative stress on macroalgae. From these studies it is obvious that different algal species have varying strategies against oxidative stress which correlate with zonation on the shore. [Copyright &y& Elsevier]

Mineral content was determined in several brown (Fucus vesiculosus, Laminaria digitata, Undaria pinnatifida) and red (Chondrus crispus, Porphyra tenera) edible marine sea vegetables. Seaweeds contained high proportions of ash (21.1–39.3%) and sulphate (1.3–5.9%). In brown algae, ash content (30.1–39.3%) was higher than in red algae (20.6–21.1%). Atomic absorption spectrophotometry of the ashes indicated that marine seaweeds contained higher amounts of both macrominerals (8.083–17,875 mg/100g; Na, K, Ca, Mg) and trace elements (5.1–15.2 mg/100 g; Fe, Zn, Mn, Cu), than those reported for edible land plants. Edible brown and red seaweeds could be used as a food supplement to help meet the recommended daily intake of some essential minerals and trace elements. [Copyright &y& Elsevier]

[Display omitted] Biohydrogen production from marine macroalgal biomass by advanced pre-treatment strategies is considered a clean energy technology. The present study focuses on investigating the effects of sonication pre-treatment (SP) and saponin coupled sonic pre-treatment (SSP) on Ulva fasciata for enhancing the production of biohydrogen. The SP and SSP were optimized to improve the hydrolysis process during digestion. The optimized time and sonication power were found respectively as 30 min and 200 W. A high concentration of biopolymer release was noticed in SSP than SP at optimized conditions. The surfactant dosage in SSP was optimized at 0.0036 g/g TS. The effect of SSP process was assessed by estimation of COD (Chemical Oxygen Demand) and SCOD (Soluble Chemical Oxygen Demand) release. The study revealed that, at a specific energy of 36,000 KJ/Kg TS, the SCOD release was higher in SSP (1900 mg/L) than SP (1050 mg/L). The SSP process could improve the COD solubilization to 15 % more than the SP. Carbohydrate and protein release are also more in SSP than SP. The use of biosurfactants significantly reduced the energy utilization in the hydrolysis process. The SSP pre-treated Ulva fasciata biomass has yielded a higher biohydrogen of 91.7 mL/g COD which is higher compared to SP (40.5 mL/g COD) and Control (9 mL/g COD). [ABSTRACT FROM AUTHOR]

Abstract: Biosynthesis of nanoparticles is an important area in the field of nanotechnology which has economic and eco-friendly benefits over chemical and physical methods of synthesis. The present contribution deals with one pot method for synthesis of zinc oxide nanoparticles (ZnO NPs) through green process using the brown marine macroalgae Sargassum muticum (S.muticum) aqueous extract. FTIR spectra revealed the involvement of sulfate and hydroxyl moieties of polysaccharide in the formation of ZnO NPs. Pure ZnO NPs were obtained after calcination of S.muticum formed ZnO at 450°C. FESEM analysis shows that the pure ZnO NPs synthesized have hexagonal wurtzite structures and the average size ranged from 30 to 57nm. The UV–vis absorption spectra of the pure ZnO NPs exhibited absorption peaks in the UV region which were attributed to the band gap of the ZnO NPs. [Copyright &y& Elsevier]

Gadolinium (Gd) is a rare earth associated with hospital and urban wastewaters due to its application as a contrast agent for magnetic resonance imaging. In this work, the uptake of Gd from contaminated seawater by three living marine macroalgae, Ulva lactuca (Chlorophyta), Fucus spiralis (Phaeophyta) and Gracilaria sp. (Rhodophyta) was studied along 72 h. Surface analysis (FTIR), water content, kinetic modelling, and Gd quantification in seawater and biomass were performed. All species were able to accumulate Gd from seawater with 10, 157, and 500 μg Gd L−1, although green and red macroalgae performed better, following the order: green > red > brown. Removal efficiencies reached 85%, corresponding to a bioconcentration factor of 1700. In more complex solutions that intended to mimic real contaminated environments, namely mixtures with other rare earth elements (Y, La, Ce, Pr, Nd, Eu, Tb, Dy), and with potentially toxic elements commonly found in wastewaters (Cr, Ni, Cu, Cd, Hg, Pb), at two salinities (10 and 30), the macroalgae kept its efficiency: 84% and 88% of removal by green and red macroalgae, respectively. Overall, findings evidence that living macroalgae could be a countermeasure to the increasing anthropogenic enrichment of Gd observed in the aquatic environment. Unlabelled Image • Gadolinium uptake by 3 living macroalgae under realistic conditions was studied. • Removal went up to 88% and bioconcentration up to 1700 (dose-reliant accumulation). • Surface area, protein content and metabolism explained F. spiralis worst performance. • Potentially toxic elements enhanced removal while rare earths slightly inhibited it. • No noticeable physiological changes in macroalgae were observed. [ABSTRACT FROM AUTHOR]