Antibacterial Activities of the Algal Bromophenol Methylrhodomelol Against Pseudomonas aeruginosa.

Methylrhodomelol (1: ) is a bromophenol from the red alga Vertebrata lanosa that has been associated with antimicrobial properties. The aim of the current study was, therefore, to assess the antimicrobial potential of this compound in more detail against the gram-negative pathogen Pseudomonas aeruginosa. 1: exerted weak bacteriostatic activity against different strains when grown in minimal medium, whereas other phenolics were inactive. In addition, 1: (35 and 10 µg/mL) markedly enhanced the susceptibility of multidrug-resistant P. aeruginosa toward the aminoglycoside gentamicin, while it did not affect the viability of Vero kidney cells up to 100 µM. Finally, pyoverdine release was reduced in bacteria treated at sub-inhibitory concentration, but no effect on other virulence factors was observed. Transcriptome analysis of treated versus untreated P. aeruginosa indicated an interference of 1: with bacterial carbon and energy metabolism, which was corroborated by RT-qPCR and decreased ATP-levels in treated bacteria. In summary, the current study characterized the antibacterial properties of methylrhodomelol, revealed its potential as an adjuvant to standard antibiotics, and generated a hypothesis on its mode of action.

Effect of Post-Extraction Ultrasonication on Compositional Features and Antioxidant Activities of Enzymatic/Alkaline Extracts of Palmaria palmata.

Palmaria palmata is a viable source of nutrients with bioactive properties. The present study determined the potential role of post-extraction ultrasonication on some compositional features and antioxidant properties of enzymatic/alkaline extracts of P. palmata (EAEP). No significant difference was detected in terms of protein content and recovery, as well as the amino acid composition of the extracts. The nitrogen-to-protein conversion factor of 5 was found to be too high for the seaweed and EAEP. The extracts sonicated by bath for 10 min and not sonicated showed the highest and lowest total phenolic contents (p < 0.05), respectively. The highest radical scavenging and lowest metal-chelating activities were observed for the non-sonicated sample, as evidenced by IC50 values. The extract sonicated by bath for 10 min showed the most favorable in vitro antioxidant properties since its radical scavenging was not significantly different from that of the not-sonicated sample (p > 0.05). In contrast, its metal-chelating activity was significantly higher (p < 0.05). To conclude, post-extraction ultrasonication by an ultrasonic bath for 10 min is recommended to increase phenolic content and improve the antioxidant properties of EAEP.

Isolation of Mycosporine-like Amino Acids from Red Macroalgae and a Marine Lichen by High-Performance Countercurrent Chromatography: A Strategy to Obtain Biological UV-Filters.

Marine organisms have gained considerable biotechnological interest in recent years due to their wide variety of bioactive compounds with potential applications. Mycosporine-like amino acids (MAAs) are UV-absorbing secondary metabolites with antioxidant and photoprotective capacity, mainly found in organisms living under stress conditions (e.g., cyanobacteria, red algae, or lichens). In this work, five MAAs were isolated from two red macroalgae (Pyropia columbina and Gelidium corneum) and one marine lichen (Lichina pygmaea) by high-performance countercurrent chromatography (HPCCC). The selected biphasic solvent system consisted of ethanol, acetonitrile, saturated ammonium sulphate solution, and water (1:1:0.5:1; v:v:v:v). The HPCCC process for P. columbina and G. corneum consisted of eight separation cycles (1 g and 200 mg of extract per cycle, respectively), whereas three cycles were performed for of L. pygmaea (1.2 g extract per cycle). The separation process resulted in fractions enriched with palythine (2.3 mg), asterina-330 (3.3 mg), shinorine (14.8 mg), porphyra-334 (203.5 mg) and mycosporine-serinol (46.6 mg), which were subsequently desalted by using precipitation with methanol and permeation on a Sephadex G-10 column. Target molecules were identified by HPLC, MS, and NMR.

Development of a Sequential Fractionation-and-Recovery Method for Multiple Anti-Inflammatory Components Contained in the Dried Red Alga Dulse (Palmaria palmata).

A separation process was established to sequentially fractionate and recover three anti-inflammatory components derived from sugars, phycobiliprotein, and chlorophyll from the hot-air-dried thalli of the red alga dulse (Palmaria palmata). The developed process consisted of three steps, without the use of organic solvents. In Step I, the sugars were separated by disrupting the cell wall of the dried thalli with a polysaccharide-degrading enzyme, and a sugar-rich extract (E1) was obtained by precipitating the other components, which were simultaneously eluted by acid precipitation. In Step II, the residue suspension from Step I was digested with thermolysin to obtain phycobiliprotein-derived peptides (PPs), and a PP-rich extract (E2) was obtained by separating the other extracts using acid precipitation. In Step III, solubilized chlorophyll was obtained by heating the residue, which was acid-precipitated, neutralized, and re-dissolved to concentrate the chlorophyll-related components (Chls)-rich extract (E3). These three extracts suppressed inflammatory-cytokine secretion by lipopolysaccharide (LPS)-stimulated macrophages, confirming that the sequential procedure had no negative effects on the activities of any of the extracts. The E1, E2, and E3 were rich in sugars, PPs, and Chls, respectively, indicating that the anti-inflammatory components were effectively fractionated and recovered through the separation protocol.

Fillet Fish Fortified with Algal Extracts of Codium tomentosum and Actinotrichia fragilis, as a Potential Antibacterial and Antioxidant Food Supplement.

With respect to the potential natural resources in the marine environment, marine macroalgae or seaweeds are recognized to have health impacts. Two marine algae that are found in the Red Sea, Codium tomentosum (Green algae) and Actinotrichia fragilis (Red algae), were collected. Antibacterial and antioxidant activities of aqueous extracts of these algae were evaluated in vitro. Polyphenols from the extracts were determined using HPLC. Fillet fish was fortified with these algal extracts in an attempt to improve its nutritional value, and sensory evaluation was performed. The antibacterial effect of C. tomentosum extract was found to be superior to that of A. fragilis extract. Total phenolic contents of C. tomentosum and A. fragilis aqueous extract were 32.28 ± 1.63 mg/g and 19.96 ± 1.28 mg/g, respectively, while total flavonoid contents were 4.54 ± 1.48 mg/g and 3.86 ± 1.02 mg/g, respectively. Extract of C. tomentosum demonstrates the highest antioxidant activity, with an IC50 value of 75.32 ± 0.07 µg/mL. The IC50 of L-ascorbic acid as a positive control was 22.71 ± 0.03 µg/mL. The IC50 values for inhibiting proliferation on normal PBMC cells were 33.7 ± 1.02 µg/mL and 51.0 ± 1.14 µg/mL for C. tomentosum and A. fragilis, respectively. The results indicated that both algal aqueous extracts were safe, with low toxicity to normal cells. Interestingly, fillet fish fortified with C. tomentosum extract demonstrated the greatest overall acceptance score. These findings highlight the potential of these seaweed species for cultivation as a sustainable and safe source of therapeutic compounds for treating human and fish diseases, as well as effective food supplements and preservatives instead of chemical ones after performing in vivo assays.

The Lebanese Red Algae Jania rubens: Promising Biomolecules against Colon Cancer Cells.

Colorectal cancer (CRC) is ranked the second most lethal type of tumor globally. Thus, developing novel anti-cancer therapeutics that are less aggressive and more potent is needed. Recently, natural bioactive molecules are gaining interest as complementary and supportive antineoplastic treatments due to their safety, effectiveness, and low cost. Jania rubens (J. rubens) is a red coral seaweed abundant in the Mediterranean and bears a significant pharmacological essence. Despite its therapeutic potential, the natural biomolecules extracted from this alga are poorly identified. In this study, the proximal analysis revealed high levels of total ash content (66%), 11.3% proteins, 14.5% carbohydrates, and only 4.5% lipids. The elemental identification showed magnesium and calcium were high among its macro minerals, (24 ± 0.5 mg/g) and (33 ± 0.5 mg/g), respectively. The Chlorophyll of J. rubens was dominated by other pigments with (0.82 ± 0.02 mg/g). A 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay identified effective antioxidant activity in various J. rubens extracts. More importantly, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tetrazolium reduction and wound healing assays indicate that organic extracts from J. rubens significantly counteract the proliferation of colon cancer cell lines (HCT-116 and HT-29) and inhibit their migratory and metastatic properties in a dose and time-dependent manner. Overall, this study provides insight into the physicochemical properties of red seaweed, J. rubens, and identifies its significant antioxidant, cytotoxic, and anti-migratory potential on two colorectal cell lines, HCT-116 and HT-29.

Mechanisms of the ethanol extract of Gelidium amansii for slow aging in high-fat male Drosophila by metabolomic analysis.

Gelidium amansii (GA) is a kind of red alga homologous to medicine and food and is distributed all over the world. Studies on GA are mainly focused on its polysaccharides, with little research on the ethanol extract. The ethanol extract of Gelidium amansii (GAE) was subjected to a reverse-phase column to obtain 7 components. Among them, 100% methanol solution (GAM), enriched with phytene-1,2-diol, exhibited the strongest DPPH free radical scavenging activity (IC50 = 0.17 mg mL-1). Subsequently, high-fat male flies (HMFs) were used as a model to explore the antioxidant and anti-aging effects of GAM in vivo. Studies showed that GAM can effectively prolong the lifespan of HMFs. When GAM concentrations were 0.2 and 1.0 mg mL-1, the average lifespan of HMFs was increased by 28.7 and 40.7%, respectively, while the longest lifespan of HMFs was increased by 20.55% and 32.88%, respectively. Further research revealed that GAM can significantly downregulate the levels of malondialdehyde (MDA) and protein carbonyl (PCO), and can significantly upregulate the levels of catalase (CAT) and total superoxide dismutase (T-SOD). In addition, by analyzing differential metabolites, we found that GAM relieves aging caused by oxidative stress by regulating amino acid, lipid, sugar, and energy metabolism. The GAM group significantly regulated the levels of adenine, cholic acid, glutamate, L-proline, niacin, and stachyose which tend to recover to the levels of the normal diet male fly (NMF) group. In general, our research provides ideas for the high-value utilization of GA and provides a lead compound for the research and development of anti-aging food or medicine.

Multi-Step Enzymatic Production and Purification of 2-Keto-3-Deoxy-Galactonate from Red-Macroalgae-Derived Agarose.

2-keto-3-deoxy sugar acids, which have potential as precursors in medicinal compound production, have gained attention in various fields. Among these acids, 2-keto-3-deoxy-l-galactonate (KDGal) has been biologically produced from D-galacturonate originating from plant-derived pectin. KDGal is also found in the catabolic pathway of 3,6-anhydro-l-galactose (AHG), the main component of red-algae-derived agarose. AHG is converted to 3,6-anhydrogalactonate by AHG dehydrogenase and subsequently isomerized to KDGal by 3,6-anhydrogalactonate cycloisomerase. Therefore, we used the above-described pathway to produce KDGal from agarose. Agarose was depolymerized to AHG and to agarotriose (AgaDP3) and agaropentaose (AgaDP5), both of which have significantly higher molecular weights than AHG. When only AHG was converted to KDGal, AgaDP3 and AgaDP5 remained unreacted. Finally, KDGal was effectively purified from the enzymatic products by size-exclusion chromatography based on the differences in molecular weights. These results show that KDGal can be enzymatically produced and purified from agarose for use as a precursor to high-value products.

Anticancer and antimicrobial activity of biosynthesized Red Sea marine algal silver nanoparticles.

Biosynthesis of silver nanoparticles (AgNPs) is emerging as a simple and eco-friendly alternative to conventional chemical synthesis methods. The role of AgNPs is expanding as antimicrobial and anticancer agents, sensors, nanoelectronic devices, and imaging contrast agents. In this study, biogenic AgNPs were synthesized using extracts of different marine algae species, including Ulva rigida (green alga), Cystoseira myrica (brown alga), and Gracilaria foliifera (red alga), as reducing and capping agents. The Physiochemical properties, cytotoxicity, anticancer and antimicrobial activities of the biosynthesized AgNPs were assessed. Surface plasmonic bands of the biosynthesized AgNPs capped with U. rigida, C. myrica, and G. foliifera extracts were visually observed to determine a colour change, and their peaks were observed at 424 nm, 409 nm, and 415 nm, respectively, by UV-Vis spectroscopy; transmission electron microscopy (TEM) indicated an almost spherical shape of AgNPs with nanoscale sizes of 12 nm, 17 nm, and 24 nm, respectively. Fourier transform-infrared (FTIR) spectroscopy analysis suggested that different molecules attached to AgNPs through OH, C=O, and amide groups. The major constituents of the aqueous algal extracts included, terpenoids, polyphenols, sulfonates, polysaccharides, fatty acids, chlorophylls, amide proteins, flavonoids, carotenoids, aliphatic fluoro compounds, volatile compounds, alkalines, pyruvic acid and agar groups. The cytotoxicity and anticancer activities of the biosynthesized AgNPs were assessed using Artemia salina nauplii, normal skin cell lines (HFb-4), and breast cancer cell lines (MCF-7 cell line). The lethality was found to be directly proportional to the AgNP concentration. The IC50 values of C. myrica and G. foliifera AgNPs against A. saline nauplii were 5 and 10 µg ml-1 after 4 h and 16 h, respectively, whereas U. rigida AgNPs did not exhibit cytotoxic effects. Anticancer activity of the biosynthesized AgNPs was dose dependent. The IC50 values of the biosynthesized AgNPs were 13, 13, and 43 µg ml-1 for U. rigida, C. myrica, and G. foliifera, respectively. U. rigida AgNPs particularly exhibited potent anticancer activity (92.62%) against a human breast adenocarcinoma cell line (MCF-7) with high selectivity compared the normal cells (IC50 = 13 µg/ml, SI = 3.2), followed by C. myrica AgNPs (IC50 = 13 µg/ml, SI = 3.07). Furthermore, the biosynthesized AgNPs exhibited strong antifungal activity against dermatophyte pathogenic moulds and mild antibacterial activity against the food borne pathogen bacteria. The highest antimicrobial activity was recorded for the U. rigida AgNPs, followed by those capped with C. myrica and G. foliifera extracts, respectively. AgNPs capped with the U. rigida extract exhibited the highest antimicrobial activity against Trichophyton mantigrophytes (40 mm), followed by Trichosporon cataneum (30 mm) and E. coli (19 mm), with minimal lethal concentration of 32 and 64 µg ml-1 respectively. The study finally revealed that extracts of marine algal species, particularly U. rigida extracts, could be effectively used as reducing agents for the green synthesis of AgNPs. These AgNPs are considered efficient alternative antidermatophytes for skin infections and anticancer agents against the MCF-7 cell line.

An Update on Natural Antileishmanial Treatment Options from Plants, Fungi and Algae.

Efficient drugs for the treatment of leishmaniasis, which is classified as a neglected tropical disease, are sought for. This review covers potential drug candidates from natural plant, fungus and algae sources, which were described over the last six years. The identification of these natural antileishmanials often based on the knowledge of traditional medicines. Crucial insights into the activities of these natural remedies against Leishmania parasites and against infections caused by these parasites in laboratory animals or patients are provided and compared with selected former active examples published more than six years ago. In addition, immuno-modulatory natural antileishmanials and recent developments on combination therapies including natural products and approved antileishmanials are discussed. The described natural products revealed promising data warranting further efforts on the discovery and development of new antileishmanials based on patterns from nature.

New Active Packaging Based on Biopolymeric Mixture Added with Bacteriocin as Active Compound.

The objective of this work was to develop a chitosan/agar-agar bioplastic film incorporated with bacteriocin that presents active potential when used as food packaging. The formulation of the film solution was determined from an experimental design, through the optimization using the desirability function. After establishing the concentrations of the biopolymers and the plasticizer, the purified bacteriocin extract of Lactobacillus sakei was added, which acts as an antibacterial agent. The films were characterized through physical, chemical, mechanical, barrier, and microbiological analyses. The mechanical properties and water vapor permeability were not altered by the addition of the extract. The swelling property decreased with the addition of the extract and the solubility increased, however, the film remained intact when in contact with the food, thus allowing an efficient barrier. Visible light protection was improved by increased opacity and antibacterial capacity was effective. When used as Minas Frescal cream cheese packaging, it contributed to the increase of microbiological stability, showing a reduction of 2.62 log UFC/g, contributing a gradual release of the active compound into the food during the storage time. The film had an active capacity that could be used as a barrier to the food, allowing it to be safely packaged.

Synthesis and evaluation of Grateloupia Livida polysaccharides-functionalized selenium nanoparticles.

Grateloupia Livida polysaccharides-functionalized selenium nanoparticles (GLP-SeNPs) have been successfully prepared in a simple redox system of sodium selenite and ascorbic acid. The size, morphology, structure, stability and thermal behavior were analyzed by various characterization methods. These results showed that, GLP-SeNPs (particle size of 115.54 nm) prepared in optimal synthesis conditions (temperature of 45 °C, reaction time of 3 h, GLP concentration of 1.0 mg/mL and ascorbic acid concentration of 0.04 M) obtained by orthogonal experiments were uniform spherical and could be stable for 30 days at 4 °C. GLP-SeNPs exhibited significant scavenging ability on DPPH, ABTS, hydroxyl radical and superoxide anion radical when compared to GLP and Na2SeO3. GLP-SeNPs showed selective cytotoxicity toward various human cancer cells, but not normal cells. Besides, GLP-SeNPs exhibited low oral acute toxicity. Taken together, GLP-SeNPs might be used as potential diet nutritional supplement or anticancer agent.

Agarose oligosaccharide- silver nanoparticle- antimicrobial peptide- composite for wound dressing.

Marine polysaccharides or oligosaccharides have potential to promote wound healing due to their biocompatibility and physicochemical properties. However, microbial infection delays wound healing process, and novel antimicrobial wound dressings are urgently needed. Here, agarose oligosaccharides (AGO) obtained from marine red algae were used as a reducing and stabilizer for green synthesis of silver nanoparticles (AgNPs), and further successfully connected with odorranain A (OA), one of antimicrobial peptides (AMPs), to obtain a novel composite nanomaterial (AGO-AgNPs-OA). Transmission electron microscopy (TEM) and Malvern particle size analyzer showed that AGO-AgNPs-OA was spherical or elliptic with average size of about 100 nm. Circular dichroism (CD) spectroscopy showed that AGO-AgNPs stabilized the α-helical structure of OA. AGO-AgNPs-OA showed stronger anti-bacterial activities than AGO-AgNPs, and had good biocompatibility and significant promoting effect on wound healing. Our data suggest that AMPs conjugated marine oligosaccharides and AgNPs may be effective and safe antibacterial materials for wound therapy.

An Overview to the Health Benefits of Seaweeds Consumption.

Currently, seaweeds are gaining major attention due to the benefits they give to our health. Recent studies demonstrate the high nutritional value of seaweeds and the powerful properties that seaweeds' bioactive compounds provide. Species of class Phaeophyceae, phylum Rhodophyta and Chlorophyta possess unique compounds with several properties that are potential allies of our health, which make them valuable compounds to be involved in biotechnological applications. In this review, the health benefits given by consumption of seaweeds as whole food or by assumption of bioactive compounds trough natural drugs are highlighted. The use of seaweeds in agriculture is also highlighted, as they assure soils and crops free from chemicals; thus, it is advantageous for our health. The addition of seaweed extracts in food, nutraceutical, pharmaceutical and industrial companies will enhance the production and consumption/usage of seaweed-based products. Therefore, there is the need to implement the research on seaweeds, with the aim to identify more bioactive compounds, which may assure benefits to human and animal health.

Ultrasound-Assisted Water Extraction of Mastocarpus stellatus Carrageenan with Adequate Mechanical and Antiproliferative Properties.

Ultrasound-assisted water extraction was optimized to recover gelling biopolymers and antioxidant compounds from Mastocarpus stellatus. A set of experiments following a Box-Behnken design was proposed to study the influence of extraction time, solid liquid ratio, and ultrasound amplitude on the yield, sulfate content, and thermo-rheological properties (viscoelasticity and gelling temperature) of the carrageenan fraction, as well as the composition (protein and phenolic content) and antiradical capacity of the soluble extracts. Operating at 80 °C and 80 kHz, the models predicted a compromise optimum extraction conditions at ~35 min, solid liquid ratio of ~2 g/100 g, and ultrasound amplitude of ~79%. Under these conditions, 40.3% carrageenan yield was attained and this product presented 46% sulfate and good mechanical properties, a viscoelastic modulus of 741.4 Pa, with the lowest gelling temperatures of 39.4 °C. The carrageenans also exhibited promising antiproliferative properties on selected human cancer cellular lines, A-549, A-2780, HeLa 229, and HT-29 with EC50 under 51.9 µg/mL. The dried soluble extract contained 20.4 mg protein/g, 11.3 mg gallic acid eq/g, and the antiradical potency was equivalent to 59 mg Trolox/g.

Seaweed dietary supplements enhance the innate immune response of the mottled rabbitfish, Siganus fuscescens.

Disease is one of the major bottlenecks for aquaculture development, costing the industry in excess of US $6 billion each year. The increase in pressure to phase out some traditional approaches to disease control (e.g. antibiotics) is pushing farmers to search for alternatives to treat and prevent disease outbreaks, which do not have detrimental consequences (e.g. antibiotic resistance). We tested the effects of eleven seaweed species and four established fish immunostimulants on the innate immune response (cellular and humoral immunity) of the rabbitfish Siganus fuscescens. All supplements including different seaweeds from the three groups (Chlorophyta, Phaeophyta and Rhodophyta) were included in the fish pellet at 3% (by weight) and had variably positive effects across the four innate immune parameters we measured compared to control fish. Diets supplemented with the red seaweed Asparagopsis taxiformis and the brown seaweed Dictyota intermedia led to the largest boosts in humoral and cellular innate immune defences, including particularly significant increases in haemolytic activity. Diets supplemented with Ulva fasciata also led to promising positive effects on the fish innate immune responses. We conclude that dietary seaweed supplements can boost the immune response of S. fuscescens and thus the top three species highlighted in this study should be further investigated for this emerging aquaculture species and other fish species.

Can algae contribute to the war with Covid-19?

The world at large is facing a new threat with the emergence of the Coronavirus Disease 2019 (COVID-19) pandemic. Though imperceptible by the naked eye, the medical, sociological and economical implications caused by this newly discovered virus have been and will continue to be a great impediment to our lives. This health threat has already caused over two million deaths worldwide in the span of a year and its mortality rate is projected to continue rising. In this review, the potential of algae in combating the spread of COVID-19 is investigated since algal compounds have been tested against viruses and algal anti-inflammatory compounds have the potential to treat the severe symptoms of COVID-19. The possible utilization of algae in producing value-added products such as serological test kits, vaccines, and supplements that would either mitigate or hinder the continued health risks caused by the virus is prominent. Many of the characteristics in algae can provide insights on the development of microalgae to fight against SARS-CoV-2 or other viruses and contribute in manufacturing various green and high-value products.

The methanol extract of red algae, Dichotomaria obtusata, from Persian Gulf promotes in vitro osteogenic differentiation of bone marrow mesenchymal stem cells; a biological and phytochemical study.

OBJECTIVES: Osteoporosis is a major public health problem that is appeared with increasing age. This study evaluated the effect of the algae Dichotomaria obtusata methanol extract on osteogenic differentiation of the cultured bone marrow mesenchymal stem cells (BMMSCs) in vitro and analyzed the algae methanol extract to find out the potent beneficial components. METHODS: Dichotomaria obtusata were collected from the coastal area of Bushehr City in the Persian Gulf, Iran. The expression of osteogenesis-related genes was examined using real-time PCR. The formation of calcium deposits in differentiated MSCs was examined by Alizarin R staining. Analyses of algae extract ingredients were performed by gas chromatography-mass spectrometry (GC-MS). KEY FINDINGS: Methanol extract of the algae caused the up-regulation of osteogenic genes that were significant for Osteopontin and Osteocalcin (P < 0.05) and also led to an increase in calcium deposits and matrix mineralization in BMMSCs. The GC-MS analyses of the algae extracts resulted in the identification of steroids and essential fatty acids. CONCLUSION: The results of the study indicated that the methanol extract of D. obtusata may possess significant potentials for the prevention of osteoporosis in vitro.

A chemometric approach to characterize the aroma of selected brown and red edible seaweeds / extracts.

BACKGROUND: Information pertaining to the aromatic profile of seaweeds and seaweed extracts can provide evidence regarding their potential suitability as ingredients in processed foods. To date only limited material has been available on the volatile profiles of some seaweed species. Others in this study have not previously been described. The volatile profiles of dried brown (Himanthalia elongata, Undaria pinnatifida, Alaria esculenta) and red (Porphyra umbilicalis, Palmaria palmata) seaweeds, and a brown seaweed extract (fucoxanthin) from Laminaria japonica were investigated using a chemometric approach to collate data from volatile gas chromatography - mass spectrometry (GC-MS), direct sensory aroma evaluation, and gas-chromatography - olfactometry (GC-O) to obtain a better understanding of their volatile profile and sensory perception. RESULTS: More than 100 volatile compounds were identified by static headspace solid phase micro-extraction (HS-SPME) and thermal desorption gas chromatography - mass spectrometry (TD GC-MS). Brown seaweeds were characterized by 'grassy/herbal/floral', 'fruity', and 'fatty' aromas, red seaweeds by 'green/vegetable', 'mushroom/earthy' and 'sweet/buttery' aromas, and the fucoxanthin extract by 'rancid' and 'nutty' aromas with an overall lower intensity. Heptanal appeared to be a major odor-active compound in all samples. Other volatiles were more characteristic of each individual seaweed: hexanal, (E,Z)-2,6-nonadienal and 2-pentylfuran for H. elongata; ethyl butanoate and 2,3-butanedione for U. pinnatifida; 6-dimethylpyrazine, (E,Z)-2,6-nonadienal and sulactone for P. palmata; 1-octen-3-ol for P. umbilicalis, heptanone for A. esculenta, and 2-furanmethanol for fucoxanthin. CONCLUSION: Brown and red seaweeds had distinct sensory properties with individual seaweeds having differing volatiles and odorants. This study provides additional information that can contribute to the development of products incorporating dried seaweeds / extracts that are more acceptable to the consumer. © 2020 Society of Chemical Industry.

Enhancement of Galactose Uptake from Kappaphycus alvarezii Hydrolysate Using Saccharomyces cerevisiae Through Overexpression of Leloir Pathway Genes.

A total 42.68 g/L monosaccharide with 0.10 g/L HMF was obtained from 10% (w/v) Kappaphycus alvarezii with thermal acid hydrolysis using 350 mM HNO3 at 121 °C for 60 min and enzymatic saccharification with a 1:1 mixture of Viscozyme L and Celluclast 1.5 L for 72 h. To enhance the galactose utilization rate, fermentation was performed with overexpression of GAL1 (galactokinase), GAL7 (galactose-1-phosphate uridyltransferase), GAL10 (UDP-glucose-4-epimerase), and PGM2 (phosphoglucomutase 2) in Saccharomyces cerevisiae CEN.PK2 using CCW12 as a strong promoter. Among the strains, the overexpression of PGM2 showed twofold high galactose utilization rate (URgal) and produced ethanol 1.4-fold more than that of the control. Transcriptional analysis revealed the increase of PGM2 transcription level leading to enhance glucose-6-phosphate and fructose-6-phosphate and plays a key role in ensuring a higher glycolytic flux in the PGM2 strain. This finding shows particular importance in biofuel production from seaweed because galactose is one of the major monosaccharides in seaweeds such as K. alvarezii.