Valorization of Seaweed: Using Brown Algae Waste in Papermaking

In this work, the brown alga Dictyota dichotoma was explored as a new reinforcing material for papermaking. Performing the typical chemical tests for cellulosic substrates on D. dichotoma evidenced large amounts of ethanol:benzene extractable substances (7.2%) and ashes, algae-specific results. Also, even if lipophilic compounds are removed, brown seaweed are not a primary source of fibers because it contains low proportion of cellulose. However, its elevated content of insoluble carbohydrates (51.4%) suggest there is some potential in association with conventional cellulosic pulps, as fibrous elements contribute to sheet forming and other components fill the spaces in the paper web without noteworthy loss of strength. Extraction was carried out with clean processes: hydrogen peroxide and mixtures (hydrogen peroxide-hydrochloric acid and hydrogen peroxide-sodium perborate), sodium hydroxide and sodium hypochlorite, always aiming for low reagent concentrations, in the range of 1-12%. The results show that sodium hydroxide and sodium hypochlorite were the treatments that lead to paper sheets with better structural and mechanical properties without further bleaching or refining, thus highlighting the suitability of these algae for papermaking applications.

Bioactive Phenolic Metabolites from Adriatic Brown Algae Dictyota dichotoma and Padina pavonica (Dictyotaceae)

In this study, the influences of temperature (20, 40 and 60 °C) and extraction solvents (water, ethanol) on the ultrasound-assisted extraction of phenolics from the Adriatic macroalgae Dictyota dichotoma and Padina pavonica were studied. The extracts were analysed for major phenolic sub-groups (total phenolics, flavonoids and tannins) using spectrometric methods, while the individual phenolics were detected by HPLC. The antioxidant activities were evaluated using three methods: Ferric Reducing/Antioxidant Power (FRAP), scavenging of the stabile 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and Oxygen Radical Antioxidant Capacity (ORAC). The aim of the study was also to find the connection between the chemical composition of the extracts and their biological activity. Therefore, principal component analysis (PCA), which permits simple representation of different sample data and better visualisation of their correlations, was used. Higher extraction yields of the total phenolics, flavonoids and tannins were obtained using an alcoholic solvent, while a general conclusion about the applied temperature was not established. These extracts also showed good antioxidant activity, especially D. dichotoma extracts, with high reducing capacity (690–792 mM TE) and ORAC values (38.7–40.8 mM TE in 400-fold diluted extracts). The PCA pointed out the significant influence of flavonoids and tannins on the investigated properties. The results of this investigation could be interesting for future studies dealing with the application of these two algae in foods, cosmetics and pharmaceuticals.

Fucoxanthin and Phenolic Contents of Six Dictyotales From the Tunisian Coasts With an Emphasis for a Green Extraction Using a Supercritical CO2 Method

Dictyotales, a common taxonomic group of brown seaweeds found in warm and temperate waters, are known for their richness in bioactive metabolites. In this study, six species of Dictyotales (Dictyopteris polypodioides, Dictyota dichotoma, Dictyota fasciola, Dictyota spiralis, Padina pavonica, and Taonia atomaria) collected from the Tunisian coasts were investigated for their antioxidant potentials, based on their contents of high added-value bioactive metabolites such as fucoxanthin and polyphenols. Fucoxanthin and polyphenols were analyzed quantitatively by high-performance liquid chromatography (HPLC) and UV spectrophotometer, respectively. The antioxidant property of extracts was also determined based on their ability to scavenge 2,2-Diphenyl-1-picrylhydrazyl (DPPH’s) free radical. Thus, the highest concentrations of fucoxanthin were obtained from T. atomaria and D. polypodioides (5.53 ± 1.2 and 3.43 ± 1.3 mg⋅g–1 dry weight, respectively), while the lowest amount was from D. spiralis (0.23 ± 0.1 m mg⋅g–1 dry weight). Dictyota dichotoma and T. atomaria gave the highest total phenol content (19.3 ± 0.4 and 15.2 ± 1.1 mg GAE⋅g–1 dry weight, respectively). In the second step, supercritical carbon dioxide (ScCO2) was used as a green and environmentally safe technique for the extraction of fucoxanthin from the most abundant species D. polypodioides. The extraction of fucoxanthin by ScCO2 allowed an extraction yield ranging from 0.50 ± 0.04% to 1.32 ± 0.02%, with 60°C temperature and 50-MPa pressure as the best extraction conditions. The maximum fucoxanthin and polyphenol recovery in the extract attained 15 and 64%, respectively. The results strengthen the possible use of Dictyotales from the Mediterranean Sea as a promising source of natural ingredients of health and economic interests contributing to Blue Growth in the region.

Study of Composition and Composition of Macro Algae Habitat in the Intertidal Zone Water of Sibu Island, Nort Oba District Tidore Islands City Nort Maluku

Macro algae is a part of marine plants whose whole body is called the "thallus". Macro algae are widespread in tropical and sub-tropical waters. The purpose of this study was to determine the composition of the macro algae species, the width of the micro-habitat niches, and the overlapping of the micro-habitat niches in the intertidal zone of the waters of Sibu Island, Oba Utara District, Tidore Islands City. The data was collected using survey method using belt transects and squares measuring 1x1 m2 which are placed systematically in zigzags along the tansek belt. In this study, 20 species of macro algae were found in the waters of the island of Sibu, consisting of Halimeda macroloba, Halimeada opuntia forma chordata, Halimeda incrassata, Halimeda opuntia forma renschii, Chaetamorpha sp, Eucheuma cottonii, Sargassum duplicatum, S.polycestum, Turbina ornata, T. conoides, Padina boergesenii, Dictyota dichotoma, Amphiroa fragilissima, Acanthopora spicifera, Eucheuma denticulatum, E. spinosum, Glacilaria salicornia, Hypnea nidulans, Galaxaura apiculata. The results of the analysis of the width of the recesses showed that the macro algae species with the largest recess width were Eucheuma denticulatum with a value of 0.905, while Galaxura apiculata had the narrowest recess widths with a value of 0.200. Furthermore, based on the results of overlapping analysis of microhabitat niches, it shows that the overlap of microbaitate niches is quite large by Sargassum polycestum against Galaxaura apiculata with a value of 0.337, while the lowest was carried out by Halimeda macroloba against Galaxaura apiculata, Halimeda opuntia forma chordata against Galaxaura apiculata with a value of 0.337, while the lowest was carried out by Halimeda macroloba against Galaxaura apiculata, Halimeda opuntia forma chordata against Galaxaura apiculata, Eucheuma spinosum against Galaxaura apiculata with a value of 0.000.