Brown Seaweed Sargassum Muticum Research Articles

Enhancing brown seaweed Sargassum muticum drying using pulsed electric fields and dehydration pretreatments

The present study on the brown seaweeds Sargassum muticum focused on the application of dehydration by pressing or pulsed electric fields (PEF) pretreatment before three drying processes, namely freeze-drying, air impingement drying, and natural convection in an oven. Both pretreatments permitted to reduce significantly the initial moisture of the seaweeds with a reduction up to 50 %. The structural modifications induced by these pretreatments had a direct impact on the mechanisms of moisture retention and distribution within the seaweeds, which consequently exerted an influence on drying kinetics. The apparent moisture diffusivity for freeze-drying was significantly improved by PEF passing from 2.98 10−9 m2 s−1 to 3.62 10−9 m2 s−1 after a total disintegration. Concerning oven drying by natural convection, a dehydration by pressing will be preferred because the drying time to reach 0.45 kg kg−1 in dry basis was reduced by 61 min with this pretreatment.

Spatiotemporal variation in phenology of the invasive brown macroalga Sargassum muticum (Yendo) Fensholt and the environmental parameters relationships along four different sites on the Atlantic coast of Morocco

The alien brown seaweed Sargassum muticum (Yendo) Fensholt is currently observed along the coasts of Morocco. The present study aimed to evaluate the impact of physicochemical parameters on the distribution of S. muticum at four sites on the Atlantic coast of Morocco harvested between 2019 and 2020. This study showed that the highest biomass, thalli length, and fertility values were recorded in sampling sites characterized by optimal physicochemical (temperature, pH, and salinity) and nutrient H₃PO₄ during summer. The highest biomass values were recorded in August for Sidi Bouzid and Moulay Abdellah sites, conversely, in Saada and Jorf Lasfar sites the highest values were observed in February and March respectively. The thallus length was slightly larger in Moulay Abdellah site with 77.30 ± 14.09 cm compared with the three other sites during the summer/spring periods. Minimum thalli length was recorded in September for all studied sites. The thalli of S. muticum were fertile earlier in Sidi Bouzid and Saada during spring and peaked during the summer season for all studied sites showing a positive correlation with increasing temperature.Finally, the collected data shows that indeed physicochemical parameters influence bioecological parameters. Thus, contributed to a better understanding of the temporal variation of S. muticum phenology on the Moroccan Atlantic coast, these data provide the necessary information for coastal marine management and biomonitoring program as well as sustainable utilization of this renewable marine resource.

The establishment of the invasive non-native macroalga Sargassum muticum in the north of Scotland

Abstract The spread of the brown seaweed Sargassum muticum is one of the best documented invasions of a non-native marine species. Observation of a potentially established population of S. muticum in the Orkney Islands archipelago, located off the northern coast of Scotland, was reported by recreational snorkellers in 2019 and 2020. The present study summarises a focussed investigation to confirm its presence and current local distribution, using data from 46 survey sites monitored as a part of the Orkney Islands Council Harbour Authority monitoring programme. Findings in this study represent the most northerly record of an established population of S. muticum in the United Kingdom, extending the latitudinal range in this country by 1.44° (159 km) northwards, and indicate only localised presence of this species. Analysis of a partial cytochrome oxidase I gene sequence confirmed the visual species identification. Possible vectors of introduction, gaps in the geographic range, local ecological and economic impacts, and the potential ameliorating factor of deep rockpools on wave exposed shores for S. muticum are discussed.

Synthesis, process optimization and characterization of gold nanoparticles using crude fucoidan from the invasive brown seaweed Sargassum muticum

Crude fucoidans from Sargassum muticum obtained by hot water extraction at 40–80 °C were used for the synthesis of gold nanoparticles (AuNPs). The effect of operation temperature on the yield and properties of the extract was determined. The alginate fraction partially coextracted precipitated as calcium alginate and showed rheological properties slightly lower than those of commercial alginates reported elsewhere. The fraction of fucoidan with a larger amount of sulfate, obtained at 60 °C (45% saccharide, 22% fucose, 24% sulfate), also contained 8.5% phlorotannins and 3% protein, as well as showing 37% the 2,2-azinobis(3-ethyl-benzothiazoline-6-sulfonate) (ABTS) radical scavenging capacity of Trolox. This soluble product was used for optimization during the synthesis of AuNPs. Several reaction conditions were tested until the obtainment of homogeneous nanoparticles. The characterization of the synthesized nanoparticles was performed employing ultraviolet-visible spectroscopy, Z potential, transmission electron microscopy and Fourier transformed infrared spectroscopy.

Insecticidal, antibacterial and dye adsorbent properties of Sargassum muticum decorated nano-silver particles

Marine algae contain many bioactive constituents. In the current research, the brown seaweed Sargassum muticum was collected from Red Sea and its extract used as a capping agent for the formulation of biocompatible stable silver nanoparticles (AgNPs). The seaweed-fabricated AgNPs were studied through UV–vis, TEM, XRD, EDX, FTIR and Zeta potential analyses. The chemical constituents of S. muticum extract were evaluated by RP-HPLC and 1H NMR. Both seaweed extract and AgNPs had mosquito larvicidal and adulticidal activities. The seaweed-fabricated AgNPs induced high larval mortality against mosquitoes from both Indian and Saudi Arabian strains when compared to the seaweed extract. The LC50 values of AgNPs against the Indian strains of Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi were 43.9, 35.9 and 27.0 μg/ml, respectively; those against the Saudi Arabian strains of Ae. aegypti and Cx. pipiens were 110.4 and 126.2 μg/ml, respectively. In adulticidal experiments, the LC50 values of S. muticum-fabricated AgNPs against Indian strains of Cx. quinquefasciatus, Ae. aegypti and An. stephensi were 42.3, 34.3 and 29.7 µg/ml, respectively, whereas those against the Saudi Arabian strains of Ae. aegypti and Cx. pipiens were 86.4 and 120.0 µg/ml, respectively. Minimal doses of seaweed-fabricated AgNPs were highly effective in inhibiting the growth of Bacillus subtilis (11.25 mm inhibition zone), Escherichia coli (13.35 mm), Klebsiella pneumoniae (14.24 mm) and Salmonella typhi (12.23 mm). Additionally, the seaweed extract was highly efficient to adsorb methylene blue (MB) and methyl orange (MO) dyes. In conclusion, the S. muticum extract revealed to be an effective capping agent to fabricate AgNPs to be industrially used for the control of deadly mosquito vectors and as an antimicrobial and dye adsorbent agent.

Does the invasive macro-algae Sargassum muticum (Yendo) Fensholt, 1955 offer an appropriate temporary habitat for mobile fauna including non indigenous species?

The fauna inhabiting the brown seaweed Sargassum muticum was studied on a spatial scale along the Normandy coast from the Normand-Breton Gulf to the Bay of Seine (English Channel) in both shallow sandy and rocky tidal pools during the springs 2018 and 2019. In this paper, we test the following hypothesis: do the areas with dense populations of S. muticum represent an appropriate habitat for dense motile fauna including other Non-Indigenous Species (NIS)? The ALEX (ALien biotic indEX) is used to ascertain whether or not S. muticum favours the establishment of other NIS in this new habitat. Results show that the epifaunal assemblage associated with S. muticum differs between the five sampling sites. However, the fauna at all five sites is dominated by arthropoda, especially the amphipods and isopods. In addition, five non indigenous species are observed inhabiting the brown seaweed (four amphipods: Aoroides longimerus, Aoroides semicurvatus, Monocorophium acherusicum, Monocorophium sextonae and one decapod: Hemigrapsus sanguineus). In spite of the presence of Non-Indigenous Species (NIS) associated with the invasive Sargassum, the ALEX yields a high Ecological Quality Status for all the sites. Nevertheless, the results suggest that S. muticum is a suitable habitat for many invertebrates especially amphipods and isopods, while also representing a potential source of food for several local fish and cephalopod species.

Acetone Precipitation of Heterofucoidans from Sargassum muticum Autohydrolysis Extracts

The brown seaweed Sargassum muticum was processed by non isothermal autohydrolysis under conditions selected to maximize fucoidan solubilization (170 °C). Acetone precipitation was tried for recovery of fucose-containing oligosaccharides present in hydrolyzates. The acetone:hydrolyzate volume ratio influenced both yields and composition of the precipitated fractions. The sugar components were mostly found as oligomers, their content increased with acetone:hydrolyzate volume ratio 2.0 (v/v) exhibited slight. The fractions precipitated with 0.1 and 0.9 acetone volumes showed higher phenolic and sulfate content, which was positively correlated with the antiradical activity, and exhibited slightly cytotoxic activity against human colon adenocarcinoma cells. The highest volumes of acetone used led to a slight increase in the apparent viscosity as well as the elastic and viscous moduli of formulated aqueous dispersions of alginate. Steady-state and oscillatory shear measurements of above representative dispersions indicated that the alginate extracted after acetone precipitation exhibited a slight enhancement of the viscoelastic features.

Boom-bust of Sargassum muticum in northern Spain: 30 years of invasion

ABSTRACT The brown seaweed Sargassum muticum is one of the best-studied invasive marine species, although most studies are short-term and focus on the expansion phase of invasion. Here I report 30 years of observations of the invasion of the north coast of Spain by S. muticum at regional (400 km coastline) and local scales (at the site where the invasion was first detected). At the local scale, this long-term series reveals a ‘boom-bust’ process where the expansion (‘boom’) phase lasted 12 years and the decline (‘bust’) was completed in 8 years. This cycle is supported by evidence at the regional scale. The impact of S. muticum on the recipient assemblages was only moderate during the initial ‘boom’ phase of the invasion and negligible afterwards. In conclusion, 30 years after its first observation in the region, Sargassum muticum can be considered an addition to the algal flora rather than a threat to the native assemblages.

Sargassum muticum extract based on alginate biopolymer as a new efficient biological corrosion inhibitor for carbon steel in hydrochloric acid pickling environment: Gravimetric, electrochemical and surface studies

The inhibition effect of the invasive brown seaweed Sargassum muticum extract (ESM), harvested from the Atlantic coast of Morocco, against the corrosion of carbon steel (CS) in 1 M HCl medium was studied for the first time using gravimetric, electrochemical and surface techniques. The methanolic crude extract of Sargassum muticum (ESM) is rich in alginate biopolymer. The evaluation corrosion tests showed that this algal extract acts as a good mixed corrosion inhibitor for CS substrate in 1 M HCl since inhibition efficiency of 97% was reached with 1 g/L of ESM at 303 K. AC impedance findings showed that the seaweed extract adding in the corrosive electrolyte increases the polarization resistance and conversely decreases the charge capacitance at the interface. Adsorption of ESM on the substrate surface followed the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy analyses (XPS) demonstrated that the corrosion inhibition mechanism of CS substrate in 1 M HCl environment by the investigated algal extract is typical of the chemisorption process and the protective barrier is mainly formed by the adsorbed biological macromolecules.

Summer shifts of bacterial communities associated with the invasive brown seaweed Sargassum muticum are location and tissue dependent.

Seaweed-associated microbiota experience spatial and temporal shifts in response to changing environmental conditions and seaweed physiology. These shifts may result in structural, functional and behavioral changes in the host with potential consequences for its fitness. They, thus, may help the host to adapt to changing environmental conditions. The current knowledge of seasonal variation of seaweed-associated microbiota is however still limited. In this study, we explored temporal and spatial variation of microbial communities associated with the invasive brown seaweed S. muticum. We sampled in northern and southern Portugal, in September, March and July-August (summer). In addition, as (pseudo-)perennial seaweeds display seasonal reproductive phenology, we sampled various parts of the individuals to disentangle the effect of temporal changes from those due to structural development variations. The diversity and structure of associated microbial communities were determined using next generation sequencing of the variable regions V5-7 of the 16S rDNA. We expected to find differentiation in associated microbial communities between regions and sampling months, but with differences depending on the seaweed structure examined. As expected, the study revealed substantial temporal shifts in S. muticum microbiome, for instance with large abundance of Rhodobacteraceae and Loktanella in September-March but prevalence of Pirellulales during the summer months. Variations between regions and tissues were also observed: in northern Portugal and on basal structures, bacterial diversity was higher as compared to the South and apical parts. All examined seaweed structures showed temporal differences in associated microbial community structure over time, except for holdfasts between September and March. Bacteria contributing to these changes varied spatially. Conversely to all other structures, the holdfast also did not show differences in associated community structure between southern and northern regions. Our study highlights the importance of structural microscale differentiations within seaweeds hosts with regard to their associated microbial communities and their importance across temporal and spatial dimensions.

Brown Seaweed Sargassum muticum as Low-Cost Biosorbent of Methylene Blue

Biomass of the invasive seaweed Sargassum muticum harvested from the Atlantic coast of Morocco was investigated as a natural biosorbent for the removal of methylene blue (MB) dye from aqueous solutions. FTIR spectroscopy was used to examine the variability of functional groups participating in the interaction between MB and biosorbent. The zero point charge (pHZPC) of the biomass was about 5.45. The factors affecting the efficiency of the biosorption process such as the biosorbent dose, the initial solution pH, the initial dye concentration and the contact time were investigated. The theoretical monolayer saturation capacity was estimated to be 191.38 mg/g. The biosorption process was generally not dependent on pH for values ranging from 2 to 10. The biosorption occurs very fast in the first 5 min and reaches the equilibrium within 60–90 min. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. Four conventional isotherm models were applied to describe the biosorption equilibrium data and classified according to their correlation coefficients in the following order: Temkin model (R2 = 0.989) > Dubinin–Radushkevich (R2 = 0.982) > Langmuir (R2 = 0.938) > Freundlich (R2 = 0.934). The Temkin constants (KT = 0.825 L/g, bT = 43.165 J/mol) and the Dubinin–Radushkevich mean free energy (ED= 0.731 kJ/mol) indicated that the adsorption of MB onto the biomass of the invasive seaweed could be a physisorption process. The values of the thermodynamic parameters showed that adsorption is a spontaneous and exothermic process. This study suggests that biomass of the invasive seaweed Sargassum muticum has a good potential capacity to remove MB dye and it could offer promising opportunity, as a low-cost biosorbent for the treatment of cationic dye industrial wastewaters.

The paranthurid isopod crustacean Paranthura nigropunctata (Lucas, 1846): first record from the Atlantic coast of Morocco

The littoral paranthurid isopod crustacean Paranthura nigropunctata (Lucas, 1846) is recorded for the first time from the littoral of El Jadida located on the Atlantic northwest coast of Morocco. Specimens were obtained from the invasive brown seaweed Sargassum muticum and the natives Bifurcaria bifurcata and Cystoseira tamariscifolia in January 2015. This new record further confirms a significant southward distribution of P. nigropunctata and contributes to the knowledge of the biogeography of this isopod. Heretofore, the species was only known from the western and eastern Mediterranean and some Atlantic coasts. The present finding is the first of the species from Moroccan Atlantic shores, and suggests that the species may also be present in other coastal localities from Morocco and Africa. Some data on morphology, ecology and spatial distribution of the species are provided.

Acidification increases abundances of Vibrionales and Planctomycetia associated to a seaweed-grazer system: potential consequences for disease and prey digestion efficiency.

Ocean acidification significantly affects marine organisms in several ways, with complex interactions. Seaweeds might benefit from rising CO2 through increased photosynthesis and carbon acquisition, with subsequent higher growth rates. However, changes in seaweed chemistry due to increased CO2 may change the nutritional quality of tissue for grazers. In addition, organisms live in close association with a diverse microbiota, which can also be influenced by environmental changes, with feedback effects. As gut microbiomes are often linked to diet, changes in seaweed characteristics and associated microbiome can affect the gut microbiome of the grazer, with possible fitness consequences. In this study, we experimentally investigated the effects of acidification on the microbiome of the invasive brown seaweed Sargassum muticum and a native isopod consumer Synisoma nadejda. Both were exposed to ambient CO2 conditions (380 ppm, pH 8.16) and an acidification treatment (1,000 ppm, pH 7.86) for three weeks. Microbiome diversity and composition were determined using high-throughput sequencing of the variable regions V5-7 of 16S rRNA. We anticipated that as a result of acidification, the seaweed-associated bacterial community would change, leading to further changes in the gut microbiome of grazers. However, no significant effects of elevated CO2 on the overall bacterial community structure and composition were revealed in the seaweed. In contrast, significant changes were observed in the bacterial community of the grazer gut. Although the bacterial community of S. muticum as whole did not change, Oceanospirillales and Vibrionales (mainly Pseudoalteromonas) significantly increased their abundance in acidified conditions. The former, which uses organic matter compounds as its main source, may have opportunistically taken advantage of the possible increase of the C/N ratio in the seaweed under acidified conditions. Pseudoalteromonas, commonly associated to diseased seaweeds, suggesting that acidification may facilitate opportunistic/pathogenic bacteria. In the gut of S. nadejda, the bacterial genus Planctomycetia increased abundance under elevated CO2. This shift might be associated to changes in food (S. muticum) quality under acidification. Planctomycetia are slow-acting decomposers of algal polymers that could be providing the isopod with an elevated algal digestion and availability of inorganic compounds to compensate the shifted C/N ratio under acidification in their food.In conclusion, our results indicate that even after only three weeks of acidified conditions, bacterial communities associated to ungrazed seaweed and to an isopod grazer show specific, differential shifts in associated bacterial community. These have potential consequences for seaweed health (as shown in corals) and isopod food digestion. The observed changes in the gut microbiome of the grazer seem to reflect changes in the seaweed chemistry rather than its microbial composition.

Arsenic removal from water using iron-coated seaweeds

Arsenic is a semi-metal element that can enter in water bodies and drinking water supplies from natural deposits and from mining, industrial and agricultural practices. The aim of the present work was to propose an alternative process for removing As from water, based on adsorption on a brown seaweed (Sargassum muticum), after a simple and inexpensive treatment: coating with iron-oxy (hydroxides). Adsorption equilibrium and kinetics were studied and modeled in terms of As oxidation state (III and V), pH and initial adsorbate concentration. Maximum adsorption capacities of 4.2 mg/g and 7.3 mg/g were obtained at pH 7 and 20 °C for arsenite and arsenate, respectively. When arsenite was used as adsorbate, experimental evidences pointed to the occurrence of redox reactions involving As(III) oxidation to As(V) and Fe(III) reduction to Fe(II), with As(V) uptake by the adsorbent. The proposed adsorption mechanism was then based on the assumption that arsenate was the adsorbed arsenic species. The most relevant drawback found in the present work was the considerable leaching of iron to the solution. Arsenite removal from a mining-influenced water by adsorption plus precipitation was studied and compared to a traditional process of coagulation/flocculation. Both kinds of treatment provided practically 100% of arsenite removal from the contaminated water, leading at best in 12.9 μg/L As after the adsorption and precipitation assays and 14.2 μg/L after the coagulation/flocculation process.

Hexavalent Chromium Uptake from Aqueous Solutions using Raw Biomass of the Invasive Brown Seaweed Sargassum muticum from the Moroccan Shorelines: Kinetics and Isotherms

Raw biomass of the invasive Japanese brown seaweed Sargassum muticum, recently introduced to the Atlantic coast of Morocco, has been applied for the removal of hexavalent chromium Cr(VI) from aqueous solutions. Various parameters such as biomass dose, initial pH, contact time and initial Cr(VI) concentration were studied to reveal their effects on the biosorption process. At optimum values of the above mentioned parameters, total removal of Cr(VI) can be achieved within 10 min at pH 2, adsorbent dose of 0.5 g/100 mL for initial chromium ions concentration of 50 mg/L. Cr(VI) biosorption follows pseudo second-order kinetics. Adsorption isotherms were determined at room temperature and the experimental data were modelled with the Langmuir, Freundlich and Temkin isotherm equations. The isotherm data were found to be well fitted by linear Langmuir equation. The maximum sorption capacity calculated from Langmuir isotherm was estimated to be about 143 mg per gram of dry biosorbent. Thus, the biomass used in this study can be considered a promising and valuable natural adsorbent for the treatment of aqueous solution containing toxic hexavalent chromium ions.

The invasive brown seaweed Sargassum muticum as new resource for alginate in Morocco: Spectroscopic and rheological characterization

SUMMARYThe Japanese brown seaweed Sargassum muticum, recently invaded several shorelines worldwide including the Atlantic coast of Morocco with large well‐established populations. Within the framework of a sustainable strategy to control this invasive seaweed, we report on extraction yield, spectroscopic characterization and rheological properties of alginate, a commercially valuable colloid, from harvested biomass of S. muticum. Extraction yield was about 25.6% on dry weight basis. Infrared spectroscopy analysis shows that the obtained Fourier transform infrared spectra of the extracted biopolymer exhibit strong similarities with that of the commercial alginate. Furthermore, Proton nuclear magnetic resonance spectroscopy revealed that S. muticum alginate has almost equal amounts of β‐D‐mannuronic acid (M; 49%) and α‐L‐guluronic acid (G; 51%) with an M/G ratio of 1.04 and a high content of heteropolymeric MG GM diads suggesting a sequence distribution of an alternated polymer type. Rheological measurements were performed at different sodium alginate concentrations, temperatures and shear rates. The hydrocolloid exhibited pseudoplastic behavior and showed shear thinning, particularly at high solution concentration and low temperature which is consistent with the rheological behavior reported for commercial alginates. Considering the abundance of S. muticum in the Northwestern Atlantic coast of Morocco and the quality of the extracted hydrogel, this invasive species could be considered as a potential source of alginates.

Bioactive Polysaccharides Extracts fromSargassum muticumby High Hydrostatic Pressure

Sargassum muticum is an important source of bioactive polysaccharides; hence, high hydrostatic pressure (HHP) was used to improve their extraction efficiency. Response surface methodology and a Box-Behnken full factorial design were employed to assess and optimize the effects of extraction conditions on the yield, total sugars, total sulfated sugars and antioxidant activity of S. muticum extracts. The extraction yield ranged between 32 and 40.4% independently of the extraction conditions or seaweed solid/liquid ratio resulting in average increases of 3.6 to 4.8-fold for total sugars and sulfated sugars, as compared to conventional extraction. Extracts displayed improved antioxidant activities, yet maximum values were achieved under different optimum conditions of HHP processing, for example, 5–5.5 min, 300 MPa and 1 g of dry seaweed for yield. In conclusion, the optimal HHP technology conditions described in this paper enables to obtain enriched bioactive polysaccharide S. muticum extracts. Practical Applications High hydrostatic pressure (HHP) is a suitable method used to improve the extraction of natural ingredients with added value both in terms of nutritional value as in biological properties from different natural sources. In this study it was intended to evaluate the potential and the effectiveness of HHP to obtain extracts concentrated in bioactive polysaccharides from the brown seaweed Sargassum muticum. A new and possible strategy to valorize this invasive brown seaweed rich in sulfated polysaccharides with several health benefits associated. The main results have demonstrated that HHP increased extractability (higher extraction yields) and bioactivity from the seaweed S. muticum, providing extracts with higher content in polysaccharides which can be used as ingredients to develop novel functional foods.

Extraction of alginate from Sargassum muticum: process optimization and study of its functional activities

In the present study, alginate extraction from the brown seaweed Sargassum muticum was studied using single factor analysis. Response Surface Methodology-Central Composite Rotatary design (RSM-CCRD) was performed to reduce and optimize extraction temperature, alkali concentration, and consumption of solvent. Different interaction effect of three extraction factors of temperature (60–100 °C), alkali (1–5 %), and aqueous ethanol (70–100 %) were studied to reduce residual waste. The result showed that the optimum extraction yield (13.57 %) was obtained with 86 °C temperature, 3 % alkali, and 93 % ethanol. A second order polynomial equation using multiple regression analysis was developed, and the predicted extraction yield showed a high coefficient of determination (R 2 = 0.98) with the experimental alginate yield. The functionality of extracted alginate and residual supernatant left over after extraction were evaluated for total polyphenols and its antioxidant capacity. The extracted alginate was further characterized using fluorescence spectrophotometer and nuclear magnetic resonance spectroscopy. The 1H NMR data revealed that extracted alginate has an M/G ratio of 1.08 and η < 1.

Ensilage and anaerobic digestion of Sargassum muticum

The brown seaweed Sargassum muticum is an invasive species to the coasts of the British Isles, mainland Europe and North America. Attempts at its eradication and control have generally not been successful, although time-consuming and costly. Commercial exploration of this biomass for fuel could encourage its harvesting and control. Anaerobic digestion (AD) has been suggested as one of the most promising methods of exploiting algae for biofuel. The harvesting of S. muticum is seasonal; thus, there will be a need to preserve and store seaweed to supply a year-round anaerobic digestion process. Ensiling is widely used in terrestrial agriculture, but there has been little research on ensiling seaweed. The aims of this research were to: a) study the effect of ensiling on the biomethane potential of S. muticum, b) effect of size reduction prior to ensilage on leachate and other losses during ensiling and c) examine the mass balance and energy losses of ensiling S. muticum. Ensiling was found to be an effective, low energy loss method of preserving seaweed with energy loss from the biomass due to ensiling <8 % of the higher heating value of seaweed feedstock. Ensiling results in losses of salt from the biomass and the virtual total loss of organic sulphur. Size reduction of seaweed prior to ensilage reduced leachate and energy loss from the biomass. Ensiling had no significant effect on methane yield. However, methane yields from S. muticum are low ≤0.11 L CH4 g−1 volatile solid (VS) at ~25 % of the theoretical maximum. Further research is needed to establish the reasons for the recalcitrance of S. muticum, but the C:N ratio of S. muticum is low (8:1), and co-digestion with a low nitrogen content substrate such as crude glycerol may be a potential method of improving methane yield.

High-value products from macroalgae: the potential uses of the invasive brown seaweed, Sargassum muticum

Marine seaweeds represent an abundant source of natural products and may harbour valuable chemicals. The brown seaweed Sargassum muticum is an invasive species to the coasts of the British Isles, mainland Europe and North America. Attempts at its eradication and control have generally not been successful, although time-consuming and costly. Commercial exploration of this biomass for food, fuel and pharmaceutical products could encourage its harvesting and control. Though S. muticum might be unsuitable as a source of biofuel due to high ash and water content, this rapidly growing macroalga has a naturally high content of antioxidants, carotenoids and phenols, including the well-known anti-cancer compound fucoxanthin, making this species a potential source of a range of pharmaceutically relevant materials.