A Biorefinery Approach to the Biomass of the Seaweed Undaria pinnatifida (Harvey Suringar, 1873): Obtaining Phlorotannins-Enriched Extracts for Wound Healing

Fluorescent imaging and toxicology study of alga-derived carbon dots in zebrafish

With the widespread application of carbon dots (CDs) in fluorescence imaging, their toxicity has become a focal point of concern. The potential toxicity of CDs synthesized from different raw materials remains an unresolved issue. Laver and wakame, which are commonly popular sea vegetable foods rich in nutrients, were utilized to investigate whether synthetic CDs derived from these alga sources retain medicinal value. Herein, two types of fluorescent alga-derived CDs were prepared through hydrothermal synthesis using laver and wakame respectively. Zebrafish were immersed in both types of CDs to observe their fluorescence imaging effects within the zebrafish bodies. It was observed that laver-derived CDs and wakame-derived CDs exhibited similar luminescence properties but differed in terms of fish egg imaging localization. Additionally, intestinal flora sequencing revealed varying degrees of influence on the zebrafish gut microbiota by the two types of CDs, suggesting that both alga-derived CDs could enhance the abundance of intestinal flora in zebrafish.

Sequential and enzyme-assisted extraction of algal bioproducts from Ecklonia maxima

Brown algae are gaining recognition as sources of bio-compounds with diverse properties and potential applications in the food, nutraceutical, and pharmaceutical industries. Compounds such as polyphenols, alginates and fucoidan possess multiple bioactivities, including antidiabetic, antioxidant, anticancer, anti-inflammatory, and antibacterial properties. Conventional extraction methods provide low yields, posing challenges for the industrial applications of biocompounds. However, innovations are rapidly emerging to address these challenges, and one such approach is enzyme-assisted extraction. Furthermore, extracting single compounds undervalues algal biomass as valuable compounds may remain in the waste. Therefore, the aim of our study was to develop a framework for the sequential and enzyme-assisted extraction of various bio-compounds using the same biomass in a biorefinery process. The Ecklonia maxima algal biomass was defatted, and polyphenols were extracted using solid-liquid extraction with aqueous ethanol. The remaining residue was treated with an enzyme combination (Cellic® Ctec 2 and Viscozyme L) to liberate carbohydrates into solution, where an alginate and fucoidan fraction were isolated. A second alginate fraction was harvested from the residue. The phenolic fraction yielded about 11% (dry weight of extract/dry weight of seaweed biomass), the alginate fraction 35% and the fucoidan fraction 18%. These were analysed using a variety of biochemical methods. Structural analyses, including FTIR, NMR and TGA, were performed to confirm the integrity of these compounds. This study demonstrated that a sequential extraction method for various algal bioproducts is possible, which can pave the way for a biorefinery approach. Furthermore, our study primarily employed environmentally and eco-friendly extraction technologies promoting an environmentally sustainable industrial approach. This approach enhances the feasibility and flexibility of biorefinery operations, contributing to the development of a circular bio-economy.

Valorisation of the Invasive Macroalgae Undaria pinnatifida (Harvey) Suringar for the Green Synthesis of Gold and Silver Nanoparticles with Antimicrobial and Antioxidant Potential

Bacterial and fungal infections are a challenging global problem due to the reported increasing resistance of pathogenic microorganisms to conventional antimicrobials. Nanomaterials are a promising strategy to fight infections caused by multidrug-resistant microbes. In this work, gold (Au@UP) and silver (Ag@UP) nanoparticles were produced for the first time by green synthesis using an aqueous extract of the invasive macroalgae Undaria pinnatifida (UP). The nanoparticles were characterized by a wide range of physicochemical techniques. Au@UP and Ag@UP demonstrated to be spherical and crystalline with an average size of 6.8 ± 1.0 nm and 14.1 ± 2.8 nm, respectively. Carbohydrates and proteins of the UP extract may participate in the synthesis and capping of the nanoparticles. The UP extract, Ag@UP, and Au@UP were assessed for their antimicrobial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Candida auris. Ag@UP showed the highest antimicrobial activity with very low MIC and MBC values for all the tested bacteria, and Au@UP demonstrated to be very effective against biofilm-producing bacteria. The antifungal properties of both Ag@UP and Au@UP were remarkable, inhibiting hyphae formation. This study points towards a very promising biomedical exploitation of this invasive brown algae.

Seaweed Extracts to Control Postharvest Phytopathogenic Fungi in Rocha Pear

Fungal infections cause losses amounting to between 20 and 25% of the fruit industry's total outcome, with an escalating impact on agriculture in the last decades. As seaweeds have long demonstrated relevant antimicrobial properties against a wide variety of microorganisms, extracts from Asparagopsis armata, Codium sp., Fucus vesiculosus, and Sargassum muticum were used to find sustainable, ecofriendly, and safe solutions against Rocha pear postharvest fungal infections. Alternaria alternata, Botrytis cinerea, Fusarium oxysporum, and Penicillium expansum mycelial growth and spore germination inhibition activities were tested in vitro with five different extracts of each seaweed (n-hexane, ethyl acetate, aqueous, ethanolic, and hydroethanolic). An in vivo assay was then performed using the aqueous extracts against B. cinerea and F. oxysporum in Rocha pear. The n-hexane, ethyl acetate, and ethanolic extracts from A. armata showed the best in vitro inhibitory activity against B. cinerea, F. oxysporum, and P. expansum, and promising in vivo results against B. cinerea using S. muticum aqueous extract were also found. The present work highlights the contribution of seaweeds to tackle agricultural problems, namely postharvest phytopathogenic fungal diseases, contributing to a greener and more sustainable bioeconomy from the sea to the farm.

Biomolecules from Macroalgae-Nutritional Profile and Bioactives for Novel Food Product Development

Seaweed is in the spotlight as a promising source of nutrition for humans as the search for sustainable food production systems continues. Seaweed has a well-documented rich nutritional profile containing compounds such as polyphenols, carotenoids and polysaccharides as well as proteins, fatty acids and minerals. Seaweed processing for the extraction of functional ingredients such as alginate, agar, and carrageenan is well-established. Novel pretreatments such as ultrasound assisted extraction or high-pressure processing can be incorporated to more efficiently extract these targeted ingredients. The scope of products that can be created using seaweed are wide ranging: from bread and noodles to yoghurt and milk and even as an ingredient to enhance the nutritional profile and stability of meat products. There are opportunities for food producers in this area to develop novel food products using seaweed. This review paper discusses the unique properties of seaweed as a food, the processes involved in seaweed aquaculture, and the products that can be developed from this marine biomass. Challenges facing the industry such as consumer hesitation around seaweed products, the safety of seaweed, and processing hurdles will also be discussed.

A Bioactive Substance Derived from Brown Seaweeds: Phlorotannins

Phlorotannins are a type of natural active substance extracted from brown algae, which belong to a type of important plant polyphenol. Phloroglucinol is the basic unit in its structure. Phlorotannins have a wide range of biological activities, such as antioxidant, antibacterial, antiviral, anti-tumor, anti-hypertensive, hypoglycemic, whitening, anti-allergic and anti-inflammatory, etc. Phlorotannins are mainly used in the fields of medicine, food and cosmetics. This paper reviews the research progress of extraction, separation technology and biological activity of phlorotannins, which will help the scientific community investigate the greater biological significance of phlorotannins.

Seaweed proteins are nutritionally valuable components in the human diet

The global population is expected to reach 11 billion people by the year 2100 and will require sustainable sources of dietary protein. Most dietary protein originates from animal and terrestrial plant agriculture, which leads to deforestation, water pollution, and greenhouse gas emissions. Discovering alternative protein sources that are nutritionally adequate for the human diet without harmful environmental effects is imperative. Seaweeds are a promising option as they produce abundant protein with a low carbon footprint. Experimental evidence shows that seaweeds contain high concentrations of the essential amino acids (EAAs) necessary for human consumption, but seaweeds have yet to be evaluated with standardized metrics to compare their nutritional value to other protein sources. In this technical note, independent literature describing the EAA content and protein digestibility of 3 commonly consumed species of seaweeds was evaluated alongside traditional protein sources using a novel hybrid protein quality (HPQ) metric. HPQ is derived from the protein digestibility-corrected amino acid score and digestibility indispensable amino acid score but includes modifications to address the lack of in vivo digestibility data for seaweeds. Seaweed proteins are similar in quality to common plant protein sources such as peas, soy, and tree nuts. Furthermore, seaweed proteins from different species have complementary EAA profiles and can be mixed to form protein blends that are nutritionally on par with animal products such as milk and whey. Thus, seaweeds may be viable protein sources with a reduced footprint that provide beneficial ecosystem services.

Recent advances in biological properties of brown algae-derived compounds for nutraceutical applications

The increasing demand for nutraceuticals in the circular economy era has driven the research toward studying bioactive compounds from renewable underexploited resources. In this regard, the exploration of brown algae has shown significant growth and maintains a great promise for the future. One possible explanation could be that brown algae are rich sources of nutritional compounds (polyunsaturated fatty acids, fiber, proteins, minerals, and vitamins) and unique metabolic compounds (phlorotannins, fucoxanthin, fucoidan) with promising biological activities that make them good candidates for nutraceutical applications with increased value-added. In this review, a deep description of bioactive compounds from brown algae is presented. In addition, recent advances in biological activities ascribed to these compounds through in vitro and in vivo assays are pointed out. Delivery strategies to overcome some drawbacks related to the direct application of algae-derived compounds (low solubility, thermal instability, bioavailability, unpleasant organoleptic properties) are also reviewed. Finally, current commercial and legal statuses of ingredients from brown algae are presented, considering future therapeutical and market perspectives as nutraceuticals.

Multifunctional Gelatin/Chitosan Electrospun Wound Dressing Dopped with Undaria pinnatifida Phlorotannin-Enriched Extract for Skin Regeneration

The similarities of electrospun fibers with the skin extracellular matrix (ECM) make them promising structures for advanced wound dressings. Moreover, infection and resistance in wounds are a major health concern that may be reduced with antibacterial wound dressings. In this work, a multifunctional wound dressing was developed based on gelatin/chitosan hybrid fibers dopped with phlorotannin-enrich extract from the seaweed Undaria pinnatifida. The intrinsic electrospun structure properties combined with the antimicrobial and anti-inflammatory properties of phlorotannin-enrich extract will enhance the wound healing process. Electrospun meshes were produced by incorporating 1 or 2 wt% of extract, and the structure without extract was used as a control. Physico-chemical, mechanical, and biological properties were evaluated for all conditions. Results demonstrated that all developed samples presented a homogenous fiber deposition with the average diameters closer to the native ECM fibrils, and high porosities (~90%) that will be crucial to control the wound moist environment. According to the tensile test assays, the incorporation of phlorotannin-enriched extract enhances the elastic performance of the samples. Additionally, the extract incorporation made the structure stable over time since its in vitro degradation rates decreased under enzymatic medium. Extract release profile demonstrated a longstanding delivery (up to 160 days), reaching a maximum value of ~98% over time. Moreover, the preliminary antimicrobial results confirm the mesh's antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus. In terms of biological characterization, no condition presented cytotoxicity effects on hDNF cells, allowing their adhesion and proliferation over 14 days, except the condition of 2 wt% after 7 days. Overall, the electrospun structure comprising phlorotannins-enriched extract is a promising bioactive structure with potential to be used as a drug delivery system for skin regeneration by reducing the bacterial infection in the wound bed.

Microwave hydrothermal processing of Undaria pinnatifida for bioactive peptides

Microwave hydrothermal processing was employed to obtain valuable gelling or bioactive fractions from U. pinnatifida, assessing the processing conditions following a biorefinery concept. It was identified a relevant impact on the antioxidant properties, sulfate, protein and oligosaccharides content, with the highest values above 200 °C, although the maximum in fucose was obtained at 160 °C. The lowest temperature involved the highest minerals and sulfate content of the solid phases. Rheology indicated that hydrothermal treatment at 160 °C is adequate to extract alginates with structural and viscoelastic properties similar to those commercially available. The incorporation of the hydrothermal residual solids in the proposed alginate matrices favored the development of systems with potential non-food applications applications. Selected extracts, after an intensification stage using ultrasound, featured interesting biological activities for two human cancer cell lines (A2780; HeLa 229) with percentage of cellular inhibition > 83 and 57%, without positive effects on A549 and HCT-116.