Anti-microfouling Activity of Lipidic Metabolites from the Invasive Brown Alga Sargassum muticum (Yendo) Fensholt

The purification of the chloroform extract from the brown invasive macroalga Sargassum muticum, through a series of chromatographic separations, yielded 12 fractions that were tested against strains of bacteria, microalgae, and fungi involved in marine biofilm formation. The chemical composition of four (a, c, g, and k) out of the six fractions that exhibited anti-microfouling activity was investigated. Fraction a contained saturated and unsaturated linear hydrocarbons (C₁₂–C₂₇). Arachidonic acid was identified as the major metabolite in fraction c whereas fraction g contained mainly palmitic, linolenic, and palmitoleic acids. Fraction k was submitted to further purification yielding the fraction kAcaF1e that was composed of galactoglycerolipids, active against the growth of two of the four bacterial strains (Shewanella putrefaciens and Polaribacter irgensii) and all tested fungi. These promising results, in particular the isolation and the activity of galactoglycerolipids, attest the potential of the huge biomass of S. muticum as a source of new environmentally friendly antifouling compounds.     

Biochemical and antiviral activities of enzymatic hydrolysates from different invasive French seaweeds

Proliferations of green, brown and red algae appear in shallow sandy bays in North Brittany (France), and they represent a real economic constraint for the affected communities. In addition to the nuisance for residents and tourist activity, the communities must carry out systematic collection. The collected algae are spread on agricultural land spreading or composted, but these solutions reach their limits rapidly, bringing little added value to the collected algae. Seaweeds are potentially excellent sources of bioactive metabolites that could represent useful leads in the development of new functional ingredients in pharmaceutical and cosmetic industries. The aim of this study was to propose the use of an enzyme-assisted extraction as a tool to improve the extraction efficiency of antiviral compounds from three invasive French seaweeds. We selected the red Solieria chordalis, the green Ulva sp. and the brown Sargassum muticum as models for these experiments. In comparison with water extraction at 50 °C for the same time of treatment, enzymatic hydrolysis increased the yields. The data suggest the potential of enzymatic hydrolysis for producing active fractions in the function of the algal biomass, the behaviour of the cell wall, the selectivity and the action of the enzyme. Enzymatic hydrolysis appeared less effective for polyphenol recovery, but was a promising softer technique for recovering proteins, neutral sugars, uronic acids and sulphate groups. The solvent-free process, higher extraction rate and higher yields, coupled to time-saving and lower cost, make this method economical and sustainable. By using a cell viability assay, all hydrolysate fractions tested were shown to be non-toxic to Vero cells. After 3 days of treatment, no microscopically visible alteration of normal cell morphology was observed even at 500 μg mL^?1. S. chordalis extracts have an effective antiviral activity with EC₅₀ between 23.0 and 101.1 μg mL^?1 at a multiplicity of infection of 0.001 ID₅₀/cells; 100 % and 98 % cellular protection were obtained for 500 μg mL^?1 of hydrolysate extracts carbohydrase C3 and blank, respectively. Other extracts from S. chordalis inhibited viral production less effectively.     

Spatiotemporal variations of diterpene production in the brown macroalga <Emphasis Type="Italic">Bifurcaria bifurcata</Emphasis> from the western coasts of Brittany (France)

Bifurcaria bifurcata, a temperate brown macroalga, is known to show spatial fluctuations in its diterpene content along the northwestern coasts of France (Brittany). In the aim to identify environmental factors which could influence the occurrence of a particular chemical type, several populations of B. bifurcata were collected in summer 2009 and winter 2010. Their chemical composition was studied through thin layer chromatography (TLC) and nuclear magnetic resonance (NMR) analyses. Results showed that specific diterpenes are biosynthesized depending on seasons and abiotic factors, such as hydrodynamism or substratum. Exposed sites were characterized by thalli of B. bifurcata producing two main diterpenoids, bifurcane, and eleganediol, whereas thalli from sheltered sites showed crude extracts containing a major diterpene, eleganolone. On these last sites, another diterpene (bifurcanone) is only expressed in winter and was thus considered as a seasonal chemomarker. The term “chemotype” applied to a population is proposed and discussed.     

Assessment of the spatial variability of phenolic contents and associated bioactivities in the invasive alga Sargassum muticum sampled along its European range from Norway to Portugal

Sargassum muticum, an invasive brown macroalga presently distributed along European Atlantic coasts from southern Portugal to the south coast of Norway, was studied on a large geographical scale for its production of phenolic compounds with potential industrial applications and their chemical and biological activities. S. muticum can produce high biomass in Europe, which could be exploited to supply such compounds. S. muticum was collected in Portugal, Spain, France, Ireland and Norway (three sites/country) to examine the effect of the latitudinal cline and related environmental factors. Assays focused particularly on polyphenols and their activities. Crude acetone–water extracts were purified using solid phase extraction (SPE) and antioxidant and antimicrobial activities of crude extracts and semi-purified fractions measured. Total phenolic content was assessed by colorimetric Folin–Ciocalteu assay and reactive oxygen species activities by 2,2-diphenyl-1-picrylhydrazyl, reducing power, β-carotene bleaching method and xanthine oxidase assay. Antibacterial activities were tested on terrestrial and marine strains to evaluate potential use in biomedical and aquaculture fields. Purified active phlorotannins, isolated by SPE, were identified using NMR. Phenolic contents differ clearly among countries and among sites within countries. Quality did not change between countries, however, although there were some slight differences in phlorethol type. Additionally, some fractions, especially from the extreme north and south, were very active. We discuss this in relation to environmental conditions and the interest of these compounds. S. muticum represents a potential natural source of bioactive compounds and its collection could offer an interesting opportunity for the future management of this species in Europe.     

Structure/Function Analysis of a Type III Polyketide Synthase in the Brown Alga Ectocarpus siliculosus Reveals a Biochemical Pathway in Phlorotannin Monomer Biosynthesis

Brown algal phlorotannins are structural analogs of condensed tannins in terrestrial plants and, like plant phenols, they have numerous biological functions. Despite their importance in brown algae, phlorotannin biosynthetic pathways have been poorly characterized at the molecular level. We found that a predicted type III polyketide synthase in the genome of the brown alga Ectocarpus siliculosus, PKS1, catalyzes a major step in the biosynthetic pathway of phlorotannins (i.e., the synthesis of phloroglucinol monomers from malonyl-CoA). The crystal structure of PKS1 at 2.85-Å resolution provided a good quality electron density map showing a modified Cys residue, likely connected to a long chain acyl group. An additional pocket not found in other known type III PKSs contains a reaction product that might correspond to a phloroglucinol precursor. In vivo, we also found a positive correlation between the phloroglucinol content and the PKS III gene expression level in cells of a strain of Ectocarpus adapted to freshwater during its reacclimation to seawater. The evolution of the type III PKS gene family in Stramenopiles suggests a lateral gene transfer event from an actinobacterium.     

Percentage cover,biomass, distribution,and potential habitat mapping of natural macroalgae,based on high-resolution satellite data and in situ monitoring,at Libukang Island,Malasoro Bay,Indonesia

In this study, we combined remote sensing data and in situ observations to explore the potential habitats of macroalgae at Libukang Island, Indonesia. High-resolution satellite images from the GeoEye-1 were used to estimate and to map the geomorphological structures together with macroalgal species in the study area. Seasonal variations of percentage cover and biomass of macroalgae associated with substrates were investigated in May and November 2014, and June 2015, using quadrats as sampling unit. A total of nine common genera were found in the study area with three dominant genera: Sargassum, Padina, and Turbinaria. Most of macroalgae was observed in the eastern part of the Island, on several substrate types and particular oceanographic conditions (wave and current). Mean biomasses of Sargassum and Padina were high in May (1189.6 ± 455 and 166.7 ± 15.4 g DW.m^?2, respectively), while the biomass of Turbinaria was high in November (3245 ± 599.8 g DW.m^?2). The map accuracy of image classification for all typology substrates was 74.19%. Overall, approximately 62.3% of the total study area can be considered as potential for natural macroalgae habitats. Spectral response characteristic of shallow water substrates at study area based on GeoEye-1 is also presented. The results of this study exhibit a potential utilization of natural macroalgae in the study area, and provide information for a possible diversification of the use of macroalgae in Indonesia. The method could be useful for habitat management and future biomonitoring in the study area or other similar areas in Indonesia.     

In situ variability of carrageenan content and biomass in the cultivated red macroalga <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> with an estimation of its carrageenan stock at the scale of the Malasoro Bay (Indonesia) using satellite image processing

The combination of in situ measurements, hydrodynamical modeling, and satellite imagery processing presents a complete tool to improve seaweed culture management. This study measured the evolution of carrageenan content during 1-year period and estimated the biomass of Kappaphycus alvarezii at a bay scale in Malasoro Bay, Indonesia. It allowed the determination of the carrageenan stock at the scale of the bay. The carrageenan content was assessed from different parts, i.e., basal and apical, of the thallus. The biomass from T ₀ (beginning of the cultivation) to T ₄₅ (harvesting time) was determined at two seasons. Satellite image processing was performed to estimate the biomass at bay scale using parcels resulting from a semi-automatic delineation process. As no long-term in situ environmental data existed in the study area, a 3D hydrodynamical model (Model for Application at Regional Scale 3D) was implemented to obtain high-frequency salinity, water temperature, and currents. The high carrageenan yield was obtained from April to September 2015 (54–63%) when temperature ranged from 25 to 30 °C, salinity range from 33.8 to 34.8 psu, and precipitation below 0.5 mm. The biomass at bay scale was estimated at 2590 t with the highest carrageenan stock at 1.8 t ha^?1 in May 2015. The carrageenan yields and quality obtained in this study fulfilled the specification recommended for industry, and the cultivation of K. alvarezii can be carried out at optimal environmental conditions on April–September. The comprehensive approaches used in this study provide information for carrageenan stock and seaweed culture management as an important economic activity to support Indonesian coastal communities.     

Spatial and seasonal variation in density,reproductive status,length and phenolic content of the invasive brown macroalga Sargassum muticum (Yendo) Fensholt along the coast of Western Brittany (France)

The introduced macroalga Sargassum muticum (Yendo) Fensholt is currently observed along the coasts of Brittany. From February 2003 till June 2004, variations in density, reproductive status, length and phenolic content were assessed at three sites. Seasonal variability of the density was pronounced at two exposed sites (Fort Bloqué and Pointe du Diable), but absent at the sheltered site (Callot), where the macroalga was observed year-round. Thalli were generally longer in Summer (up to 73.2 ± 2.7 cm at Fort Bloqué), and had reproductive receptacles from May to September at Pointe du Diable, though only from June to September in the other stations (Callot and Fort Bloqué). Phenolic content was maximal during the reproductive period, which could be interpreted as chemical protection of the receptacles. Finally the collected data were used to explain the persistence of S. muticum and its proliferation in Brittany.     

Mechanically Enhanced Salmo salar Gelatin by Enzymatic Cross-linking: Premise of a Bioinspired Material for Food Packaging,Cosmetics, and Biomedical Applications

Marine Biotechnology - Marine animal by-products of the food industry are a great source of valuable biomolecules. Skins and bones are rich in collagen, a protein with various applications in food,...     

Haliotis tuberculata,a generalist marine herbivore that prefers a mixed diet,but with consistent individual foraging activity

While population foraging behaviour of herbivores has been extensively studied, individual choice is still poorly understood. Very few studies have focused on the individual consistency of foraging behaviour in marine herbivores. Because marine ectotherms are strongly influenced by their environment and because a mixed diet is appropriate for herbivores, we hypothesized that Haliotis tuberculata, a large marine gastropod, would not exhibit significant individual consistency in foraging activity and would display generalist food choices. To test these hypotheses, the behaviour of 120 abalone was studied using a choice test of eight macroalgal species over 3 weeks, with video recording 24 hr a day. In addition, primary components, secondary metabolites and toughness of the eight algae were measured. At the population level, food choice was mainly related to the protein composition and the toughness of the macroalgae. We found that H. tuberculata is a generalist species feeding on a variety of algae (IS = 0.64), even if 21% of the individuals can be considered to be specialists. However, in contrast to our hypothesis, highly consistent between-individual variation was observed in foraging activity (ICC = 0.81 for time spent feeding and ICC = 0.74 for number of feeding visits per day). The high individual consistency of foraging activity has some ecological and evolutionary implications currently not understood for this marine herbivore.