Trends in seaweed research

Value-added utilization technologies for seaweed processing waste in a circular economy: Developing a sustainable modern seaweed industry

The global seaweed industry annually consumes approximately 600,000 tons of dried algal biomass to produce algal hydrocolloids, yet only 15-30% of this biomass is utilized, with the remaining 70-85% discarded or released as scum or wastewater during the hydrocolloid extraction process. This residual biomass is often treated as waste and not considered for further commercial use, which contradicts the principles of sustainable development. In reality, the residual algal biomass could be employed to extract additional biochemical components, such as pigments, proteins, and cellulose, and these ingredients have important application prospects in the food sector. According to the biorefinery concept, recycling various products alongside the principal product enhances overall biomass utilization. Transitioning from traditional single-product processes to multi-product biorefineries, however, raises operating costs, presenting a significant challenge. Alternatively, developing value-added utilization technologies that target seaweed waste without altering existing processes is gaining traction among industry practitioners. Current advancements include methods such as separation and extraction of residual biomass, anaerobic digestion, thermochemical conversion, enzymatic treatment, functionalized modification of algal scum, and efficient utilization through metabolic engineering. These technologies hold promise for converting seaweed waste into alternative proteins, dietary supplements, and bioplastics for food packaging. Combining multiple technologies may offer the most effective strategy for future seaweed waste treatment. Nonetheless, most research on value-added waste utilization remains at the laboratory scale, necessitating further investigation at pilot and commercial scales.

Unveiling the culturable and non-culturable actinobacterial diversity in two macroalgae species from the northern Portuguese coast

Actinomycetota, associated with macroalgae, remains one of the least explored marine niches. The secondary metabolism of Actinomycetota, the primary microbial source of compounds relevant to biotechnology, continues to drive research into the distribution, dynamics, and metabolome of these microorganisms. In this study, we employed a combination of traditional cultivation and metagenomic analysis to investigate the diversity of Actinomycetota in two native macroalgae species from the Portuguese coast. We obtained and taxonomically identified a collection of 380 strains, which were distributed across 12 orders, 15 families, and 25 genera affiliated with the Actinomycetia class, with Streptomyces making up approximately 60% of the composition. Metagenomic results revealed the presence of Actinomycetota in both Chondrus crispus and Codium tomentosum datasets, with relative abundances of 11% and 2%, respectively. This approach identified 12 orders, 16 families, and 17 genera affiliated with Actinomycetota, with minimal overlap with the cultivation results. Acidimicrobiales emerged as the dominant actinobacterial order in both macroalgae, although no strain affiliated with this taxonomic group was successfully isolated. Our findings suggest that macroalgae represent a hotspot for Actinomycetota. The synergistic use of both culture-dependent and independent approaches proved beneficial, enabling the identification and recovery of not only abundant but also rare taxonomic members.

Integrating microalgae production into mine closure plans

Examples of successful mine closure and acceptable regional transitioning of mining areas are scarce. The recent changes to the environmental, social and governance (ESG) obligations of mining companies should help to ensure that water and land resources as well as post-mining employment opportunities are considered as a part of mine closure. Integrating microalgae production into mine closure plans is a potential opportunity for mining companies to improve many ESG outcomes. Mine sites with sufficient suitable land and water resources in high solar radiation geographies may be able to economically grow microalgae to capture atmospheric CO₂, re-purpose saline mine waters, treat acidic and near-neutral pH metalliferous waters as well as produce soil ameliorants (biofertiliser, biostimulants and/or biochar) to improve mine rehabilitation outcomes. Microalgae production facilities may also provide an alternative industry and employment opportunities to help transition regional mining towns that have become reliant on mining activities. The potential economic, environmental and social benefits of using mine-influenced water for microalgae production may offer an opportunity to successfully close and transition some mining landscapes.

Ionic Liquid-Assisted Selective Extraction and Partitioning of Biomolecules from Macroalgae

Macroalgae are a promising feedstock for several industries due to their large content of proteins and carbohydrates and the high biomass productivities. A novel extraction and fractionation concept based on ionic liquids (ILs) using Ulva lactuca as model organism is presented. Biomolecules are first extracted by means of IL-assisted mechanical shear, followed by two-phase partitioning or ultrafiltration in order to fractionate proteins and carbohydrates and to recover the IL. Ethyl methyl imidazolium dibutyl phosphate ([Emim][DBP]) is strongly selective to proteins, leading to extraction yields up to 80.4% for proteins and 30.7% for carbohydrates. The complete process, including extraction and ultrafiltration, allowed protein recovery of up to 64.6 and 15.4% of the carbohydrates in the retentate phase, while a maximum of 85.7% of the IL was recovered in the permeate phase. The native structure of the extracted proteins was preserved during extraction and fractionation as shown by gel electrophoresis. Selective extraction of proteins from macroalgae under non-denaturing conditions using ILs followed by the recovery of IL using ultrafiltration is for the first time reported. The proposed extraction-fractionation approach is simple and can be potentially applied for the biorefinery of macroalgae at the commercial scale.

Rhodophyta as Potential Sources of Photoprotectants, Antiphotoaging Compounds, and Hydrogels for Cosmeceutical Application

Seaweeds are macroscopic, multicellular, eukaryotic and photosynthetic organisms, and are a source of chemical diversity with powerful biological activities for diversified industrial applications including cosmeceuticals. Red seaweeds (Rhodophyta) are good sources of Mycosporine-like amino acids (MAA) for photoprotectant and antiphotoaging compounds. In addition, Rhodophyta are also good sources for hydrogel compounds that are used widely in the food, pharmaceutical and cosmeceutical industries as gelling agents, moisturizers or for their antiphotoaging effects. Our survey and ongoing studies revealed that the biodiversity of Indonesian Rhodophyta is rich and is a treasure trove for cosmeceutical agents including MAA and hydrogels. This study delivers valuable information for identifying potential red seaweeds in screening and searching for cosmeceutical agents.

Effect of particle size on phytochemical composition and antioxidant properties of Sargassum cristaefolium ethanol extract

Sample particle size is an important parameter in the solid-liquid extraction system of natural products for obtaining their bioactive compounds. This study evaluates the effect of sample particle size on the phytochemical composition and antioxidant activity of brown macroalgae Sargassum cristaefolium. The crude ethanol extract was extracted from dried powders of S.cristeafolium with various particle sizes (> 4000 µm, > 250 µm, > 125 µm, > 45 µm, and < 45 µm). The ethanolic extracts of S.cristaefolium were analysed for Total Phenolic Content (TPC), Total Flavonoid Content (TFC), phenolic compound concentration and antioxidant activities. The extract yield and phytochemical composition were more abundant in smaller particle sizes. Furthermore, the TPC (14.19 ± 2.08 mg GAE/g extract to 43.27 ± 2.56 mg GAE/g extract) and TFC (9.6 ± 1.8 mg QE/g extract to 70.27 ± 3.59 mg QE/g extract) values also significantly increased as particle sizes decreased. In addition, phenolic compounds epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and Epigallocatechin gallate (EGCG) concentration were frequently increased in samples of smaller particle sizes based on two-way ANOVA and Tukey's multiple comparison analysis. These results correlate with the significantly stronger antioxidant activity in samples with smaller particle sizes. The smallest particle size (< 45 µm) demonstrated the strongest antioxidant activity based on DPPH, ABTS, hydroxyl assay and FRAP. In addition, ramp function graph evaluates the desired particle size for maximum phytochemical composition and antioxidant activity is 44 µm. In conclusion, current results show the importance of particle size reduction of macroalgae samples to increase the effectivity of its biological activity.

Antioxidant and Signal-Modulating Effects of Brown Seaweed-Derived Compounds against Oxidative Stress-Associated Pathology

The biological and therapeutic properties of seaweeds have already been well known. Several studies showed that among the various natural marine sources of antioxidants, seaweeds have become a potential source of antioxidants because of their bioactive compounds. Most of the metabolic diseases are caused by oxidative stress. It is very well known that antioxidants have a pivotal role in the treatment of those diseases. Recent researches have revealed the potential activity of seaweeds as complementary medicine, which have therapeutic properties for health and disease management. Among the seaweeds, brown seaweeds (Phaeophyta) and their derived bioactive substances showed excellent antioxidant properties than other seaweeds. This review focuses on brown seaweeds and their derived major bioactive compounds such as sulfated polysaccharide, polyphenol, carotenoid, and sterol antioxidant effects and molecular mechanisms in the case of the oxidative stress-originated disease. Antioxidants have a potential role in the modification of stress-induced signaling pathways along with the activation of the oxidative defensive pathways. This review would help to provide the basis for further studies to researchers on the potential antioxidant role in the field of medical health care and future drug development.

A Review of Antiviral and Antioxidant Activity of Bioactive Metabolite of Macroalgae within an Optimized Extraction Method

Non-conventional extraction of bioactive metabolites could provide sustainable alternative techniques to preserve the potency of antioxidants and antiviral compounds extracted from macro-algae. In this paper, we first reviewed the antioxidant and antiviral potential of the active metabolites that exist in the three known macro-algae classes; Phaeophyceae, Rhodophyceae, and Chlorophyceae, and a comparison between their activities is discussed. Secondly, a review of conventional and non-conventional extraction methods is undertaken. The review then focused on identifying the optimal extraction method of sulphated polysaccharide from macro-algae that exhibits both antiviral and antioxidant activity. The review finds that species belonging to the Phaeophyceae and Rhodophceae classes are primarily potent against herpes simplex virus, followed by human immunodeficiency virus and influenza virus. At the same time, species belonging to Chlorophyceae class are recorded by most of the scholars to have antiviral activity against herpes simplex virus 1. Additionally, all three macro-algae classes exhibit antioxidant activity, the potency of which is a factor of the molecular structure of the bioactive metabolite as well as the extraction method applied.

Transcriptome analysis reveals possible antitumor mechanism of Chlorella exopolysaccharide

Microalgae, one of the most important classes of biomass producers, can produce exopolysaccharides similar to bacteria. The exopolysaccharide from Chlorella (CEPS) displays remarkable anticancer activity the mechanism of which remains to be elucidated. In this study, we analyzed the inhibitory effect of CEPS on the growth of HeLa cells. The results showed that CEPS inhibited the proliferation, decreased the viability, and changed the morphology of HeLa cells. Transcriptome analysis showed that 1894 genes were differentially expressed in the CEPS-treated group compared with the control group, including 1076 genes that were upregulated and 818 genes that were downregulated. The results of gene function enrichment analysis showed that the differentially expressed genes (DEGs) were significantly enriched in apoptosis and tumor-related biological processes and participated in several cancer and apoptosisrelated signaling pathways, including the MAPK signaling pathway, TNF signaling pathway, and the PI3K-Akt signaling pathway. The protein-protein interaction network identified 13 DEGs including PTPN11, RSAD2, ISG15, IFIT1, MX2, IFIT2, OASL, OAS1, JUN, OAS2, XAF1, ISG20, and IRF9 as hub genes. Our results suggest that CEPS is a promising therapeutic drug for the follow-up interventional therapy of cancer.

Comparative genomics of four strains of the edible brown alga, Cladosiphon okamuranus

BACKGROUND

The brown alga, Cladosiphon okamuranus (Okinawa mozuku), is one of the most important edible seaweeds, and it is cultivated for market primarily in Okinawa, Japan. Four strains, denominated S, K, O, and C, with distinctively different morphologies, have been cultivated commercially since the early 2000s. We previously reported a draft genome of the S-strain. To facilitate studies of seaweed biology for future aquaculture, we here decoded and analyzed genomes of the other three strains (K, O, and C).

RESULTS

Here we improved the genome of the S-strain (ver. 2, 130 Mbp, 12,999 genes), and decoded the K-strain (135 Mbp, 12,511 genes), the O-strain (140 Mbp, 12,548 genes), and the C-strain (143 Mbp, 12,182 genes). Molecular phylogenies, using mitochondrial and nuclear genes, showed that the S-strain diverged first, followed by the K-strain, and most recently the C- and O-strains. Comparisons of genome architecture among the four strains document the frequent occurrence of inversions. In addition to gene acquisitions and losses, the S-, K-, O-, and C-strains possess 457, 344, 367, and 262 gene families unique to each strain, respectively. Comprehensive Blast searches showed that most genes have no sequence similarity to any entries in the non-redundant protein sequence database, although GO annotation suggested that they likely function in relation to molecular and biological processes and cellular components.

CONCLUSIONS

Our study compares the genomes of four strains of C. okamuranus and examines their phylogenetic relationships. Due to global environmental changes, including temperature increases, acidification, and pollution, brown algal aquaculture is facing critical challenges. Genomic and phylogenetic information reported by the present research provides useful tools for isolation of novel strains.

Marine prebiotics: Polysaccharides and oligosaccharides obtained by using microbial enzymes

Utilization of marine algae has increased considerably over the past decades, since biodiversity within brown, red and green marine algae offers possibilities of finding a variety of bioactive compounds. Marine algae are rich sources of dietary fibre. The remarkable positive effects of seaweed dietary fibre on human body are related to their prebiotic activity over the gastrointestinal tract (GIT) microbiota. However, dietary modulation of microorganisms present in GIT can be influenced by different factors such as type and source of the dietary fibre, their molecular weight, type of extraction and purification methods employed, composition and modification of polysaccharide and oligosaccharide. This review will demonstrate evidence that polysaccharides and oligosaccharides from marine algae can be used as prebiotics, emphasizing their use in human health, their application as food and other possible applications. Furthermore, an important approach of microbial enzymes employment during extraction, modification or production of those prebiotics is highlighted.

Bayesian inference of environmental effects on seaweed production in Japan via a production-environmental suitability model

BACKGROUND

Both natural and human-induced disturbances are commonly responsible for an overall decrease of the world's seaweed. Along Japan's coastal areas, edible seaweed production has been decreasing for decades. In this study, a production-environmental suitability model to estimate the impacts of environmental factors on seaweed production was developed. The developed model not only estimates human-induced disturbances but also quantifies the impacts of environmental factors responsible for the decline of annual seaweed production. The model estimated the temporal variation in human-induced disturbances and the effects of environmental factors (i.e., rainfall, CO2 concentrations, temperature, typhoons, solar radiation, water nutrient levels, and water quality) on edible seaweeds in Japan from 1985 to 2012.

RESULTS

The environmental suitability for seaweed production in Japan was about 4.6 times greater in 1992 than in 2011, meanwhile as a result of human activities, human-induced disturbances of seaweed increased at a rate of 4.9 times faster during the period of 1998-2012 than the period of 1985-1997. The ratio of decreased production to decreased environmental suitability for seaweed production in Japan increased by 15.2% during the study years, which means that seaweed production has become more sensitive to environmental disturbances, including climatic factors and human activities in 1998-2012.

CONCLUSIONS

The results are novel in demonstrating temporal variations in the level of environmental suitability to seaweed production by using a simple mathematical model. The production-environmental suitability model successfully predicted seaweed production by reflecting the 28-year temporal variation of the observed seaweed production in Japan.

Physicochemical Characterization, Antioxidant and Immunostimulatory Activities of Sulfated Polysaccharides Extracted from Ascophyllum nodosum

Polysaccharides from Ascophyllum nodosum (AnPS) were extracted and purified via an optimized protocol. The optimal extraction conditions were as follows: extraction time of 4.3 h, extraction temperature of 84 °C and ratio (v/w, mL/g) of extraction solvent (water) to raw material of 27. The resulting yield was 9.15 ± 0.23% of crude AnPS. Two fractions, named AnP1-1 and AnP2-1 with molecular weights of 165.92 KDa and 370.68 KDa, were separated from the crude AnPS by chromatography in DEAE Sepharose Fast Flow and Sephacryl S-300, respectively. AnP1-1 was composed of mannose, ribose, glucuronic acid, glucose and fucose, and AnP2-1 was composed of mannose, glucuronic acid, galactose and fucose. AnPS, AnP1-1 and AnP2-1 exhibited high scavenging activities against ABTS radical and superoxide radical, and showed protective effect on H₂O₂-induced oxidative injury in RAW264.7 cells. Furthermore, the immunostimulatory activities of AnP1-1 and AnP2-1 were evaluated by Caco-2 cells, the results showed both AnP1-1 and AnP2-1 could significantly promote the production of immune reactive molecules such as interleukin (IL)-8, IL-1β, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α. Therefore, the results suggest that AnPS and its two fractions may be explored as a potential functional food supplement.

In silico characterization of DNA motifs associated with the differential expression of the ornithine decarboxylase gene during in vitro cystocarp development in the red seaweed Grateloupia imbricata

To gain a better understanding of the regulatory mechanism(s) modulating expression of the ornithine decarboxylase gene ODC during cystocarp development in the red seaweed Grateloupia imbricata, DNA motifs found in the 5'-upstream region of the gene were identified by in silico analysis. In addition, when infertile G. imbricata thalli were treated with ethylene, methyl jasmonate, or light as an elicitor of cystocarp development, different ODC expression patterns were observed. ODC expression correlated with (i) the elicitation (treatment) period and the period post-treatment just prior to observation of the first visible developing cystocarps (disclosure period), and (ii) the type of elicitor. Ethylene and light activated ODC expression during the elicitation period, and methyl jasmonate activated its expression during the disclosure period, suggesting that initiation and cystocarp development may involve more than one signaling pathway. In addition, expression of ODC was 450-fold greater when thalli were stimulated by ethylene compared with untreated control thalli, suggesting that G. imbricata mounts an efficient response to sense and activate ethylene-responsive signaling pathways. The patterns of differential ODC expression induced by the different elicitors during cystocarp development might provide an useful tool for characterizing the precise transcriptional regulation of ODC in G. imbricata.

On reproduction in red algae: further research needed at the molecular level

Multicellular red algae (Rhodophyta) have some of the most complex life cycles known in living organisms. Economically valuable seaweeds, such as phycocolloid producers, have a triphasic (gametophyte, carposporophyte, and tetrasporophyte) life cycle, not to mention the intricate alternation of generations in the edible "sushi-alga" nori. It is a well-known fact that reproductive processes are controlled by one or more abiotic factor(s), including day length, light quality, temperature, and nutrients. Likewise, endogenous chemical factors such as plant growth regulators have been reported to affect reproductive events in some red seaweeds. Still, in the genomic era and given the high throughput techniques at our disposal, our knowledge about the endogenous molecular machinery lags far behind that of higher plants. Any potential effective control of the reproductive process will entail revisiting most of these results and facts to answer basic biological questions as yet unresolved. Recent results have shed light on the involvement of several genes in red alga reproductive events. In addition, a working species characterized by a simple filamentous architecture, easy cultivation, and accessible genomes may also facilitate our task.

Isolation of stigmast-5,24-dien-3-ol from marine brown algae Sargassum tenerrimum and its antipredatory activity

In recent years many sterols with potent biological activity have been identified from marine sources. Here we report the isolation of stigmast-5,24-dien-3-ol (fucosterol) as a major metabolite from bioactive hexane-fraction ofSargassum tenerrimumand also investigated its ecological role.

Development of chloroplast simple sequence repeats (cpSSRs) for the intraspecific study of Gracilaria tenuistipitata (Gracilariales, Rhodophyta) from different populations

Background

Gracilaria tenuistipitata is an agarophyte with substantial economic potential because of its high growth rate and tolerance to a wide range of environment factors. This red seaweed is intensively cultured in China for the production of agar and fodder for abalone. Microsatellite markers were developed from the chloroplast genome of G. tenuistipitata var. liui to differentiate G. tenuistipitata obtained from six different localities: four from Peninsular Malaysia, one from Thailand and one from Vietnam. Eighty G. tenuistipitata specimens were analyzed using eight simple sequence repeat (SSR) primer-pairs that we developed for polymerase chain reaction (PCR) amplification.

Findings

Five mononucleotide primer-pairs and one trinucleotide primer-pair exhibited monomorphic alleles, whereas the other two primer-pairs separated the G. tenuistipitata specimens into two main clades. G. tenuistipitata from Thailand and Vietnam were grouped into one clade, and the populations from Batu Laut, Middle Banks and Kuah (Malaysia) were grouped into another clade. The combined dataset of these two primer-pairs separated G. tenuistipitata obtained from Kelantan, Malaysia from that obtained from other localities.

Conclusions

Based on the variations in repeated nucleotides of microsatellite markers, our results suggested that the populations of G. tenuistipitata were distributed into two main geographical regions: (i) populations in the west coast of Peninsular Malaysia and (ii) populations facing the South China Sea. The correct identification of G. tenuistipitata strains with traits of high economic potential will be advantageous for the mass cultivation of seaweeds.

Inhibition of LDL-oxidation and antioxidant properties related to polyphenol content of hydrophilic fractions from seaweed Halimeda Incrassata (Ellis) Lamouroux

LDL oxidation and oxidative stress are closely related to atherosclerosis. Therefore, natural antioxidants have been studied as promising candidates. In the present study, the LDL oxidation inhibition activity of bioactive compounds from Halimeda incrassata seaweed. associated to antioxidant capacity, was evaluated in vitro. Experimental work was conducted with lyophilized aqueous extract and phenolic-rich fractions of the seaweed and their effect on LDL oxidation was evaluated using heparin-precipitated LDL (hep-LDL) with exposure to Cu2+ ions and AAPH as the free radical generator. H. incrassata had a protective effect for hep-LDL in both systems and the presence of phenolic compounds contributed to the activity where phenolic-rich fractions showed significant capacity for inhibition of oxidation mediated by Cu2+ ions. The observed effect could be related to the antioxidant potential of polar fractions evidenced by reducing activity and DPPH• radical scavenging. The results obtained in vitro further support the antioxidant and LDL oxidation inhibition properties of H. incrassata and further knowledge toward future phytotherapeutic application of the seaweed.

Seasonal variation of phenolic antioxidant-mediated α-glucosidase inhibition of Ascophyllum nodosum

Ascophyllum nodosum is a brown seaweed that grows abundantly in the US Northeast coastal region. This study examined the seasonal variation of A. nodosum in phenolic contents and subsequent antioxidant, α-glucosidase and α-amylase inhibitory activities. A. nodosum was harvested monthly and extracted in hot water and the resulting extracts were spray-dried. The results indicate a clear seasonal variation in terms of phenolic content, with June and July being the highest (36.4 and 37 mg/g, respectively) and May the lowest (21.8 mg/g). The antioxidant activities, in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, correlated with the phenolic contents observed (r = 0.81), with the month of July being the highest (58%) and April the lowest (26%). Similarly in terms of Trolox equivalent, July had the highest activity (15.53 μM) and April and May the lowest (8.40 and 8.27 μM, respectively). α-glucosidase inhibitory activity exhibited a pattern similar to the phenolic contents observed with July having the highest inhibitory activity (IC(70) 2.23 μg) and April the lowest (IC(70) 26.13 μg), resulting in an inverse correlation between IC(70) values and total phenolic content (r = -0.89). Such seasonal variation is believed to be caused by temperature-related stress considering that A. nodosum is a cold water species.

Cloning and comparative studies of seaweed trehalose-6-phosphate synthase genes

The full-length cDNA sequence (3219 base pairs) of the trehalose-6-phosphate synthase gene of Porphyra yezoensis (PyTPS) was isolated by RACE-PCR and deposited in GenBank (NCBI) with the accession number AY729671. PyTPS encodes a protein of 908 amino acids before a stop codon, and has a calculated molecular mass of 101,591 Daltons. The PyTPS protein consists of a TPS domain in the N-terminus and a putative TPP domain at the C-terminus. Homology alignment for PyTPS and the TPS proteins from bacteria, yeast and higher plants indicated that the most closely related sequences to PyTPS were those from higher plants (OsTPS and AtTPS5), whereas the most distant sequence to PyTPS was from bacteria (EcOtsAB). Based on the identified sequence of the PyTPS gene, PCR primers were designed and used to amplify the TPS genes from nine other seaweed species. Sequences of the nine obtained TPS genes were deposited in GenBank (NCBI). All 10 TPS genes encoded peptides of 908 amino acids and the sequences were highly conserved both in nucleotide composition (>94%) and in amino acid composition (>96%). Unlike the TPS genes from some other plants, there was no intron in any of the 10 isolated seaweed TPS genes.

In vitro potential of Ascophyllum nodosum phenolic antioxidant-mediated alpha-glucosidase and alpha-amylase inhibition

Ascophyllum nodosum is a brown seaweed that grows abundantly in the Northeast coastal region. In this study, the potential of A. nodosum for type 2 diabetes management through antioxidant-mediated alpha-glucosidase and alpha-amylase inhibition was investigated. After the initial screening of 4 locally harvested seaweeds, A. nodosum was chosen for its highest phenolic content and was subjected to water extraction. Among extraction ratios of 50 g to 100 to 1000 mL at room temperature, 50 g/400 mL yielded the highest phenolic content of 4.5 mg/g wet weight. For evaluation of extraction temperature ranging from 20 to 80 degrees C, 50 g/400 mL was chosen as a minimum amount of extractant. Among temperatures studied, extraction at 80 degrees C resulted in the highest total phenolic contents (4.2 mg/g wet weight). All extracts had similar levels of antioxidant activity in the range of 60% to 70% in terms of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity. The 80 degrees C extract had the highest alpha-glucosidase and alpha-amylase inhibitory activity with IC(50) of 0.24 and 1.34 microg phenolics, respectively, compared to the IC(50) of acarbose, reference inhibitor, being 0.37 and 0.68 microg. The results show that fresh A. nodosum has strong alpha-glucosidase and mild alpha-amylase inhibitory activities that correlated with phenolic contents. This study suggests a nutraceutical potential of A. nodosum based on phytochemical antioxidant and antihyperglycemia activities.

Differential expression of the ornithine decarboxylase gene during carposporogenesis in the thallus of the red seaweed Grateloupia imbricata (Halymeniaceae)

This paper describes the cloning of the ornithine decarboxylase gene from a red seaweed, Grateloupia imbricata (Rhodophyta), the characterization of its expression throughout the reproductive process, and demonstrates how polyamines are involved in seaweed reproduction. In addition, the data indicate that the basal perennial and non-spore-forming thalli behave physiologically and genetically differently from the distal reproductive tissue. The common polyamines putrescine, spermidine and spermine have been associated with carposporogenesis in red seaweeds. Ornithine decarboxylase (ODC, EC 4.1.1.17) produces the diamine putrescine from the non-protein amino acid, ornithine. ODC is predominant in the synthesis of polyamines in G. imbricata. The gene encoding the ornithine decarboxylase in G. imbricata was cloned by genomic polymerase chain reaction (PCR) using degenerate primers against conserved motives, followed by chromosome walking using inverse PCR (iPCR). The encoded protein (GiODC, accession # FJ223132) was very similar to other ODCs, bearing the characteristic conserved domain of pyridoxal-dependent decarboxylases. The expression of the GiODC gene was investigated by real-time PCR and in situ hybridization (ISH), and was observed to vary according to cystocarp differentiation. It was weakly transcribed in apical parts of fertile tissue where the cystocarps are located, while the transcript levels were comparatively high in the basal part. This expression pattern correlated with the levels of free polyamines, which were higher at the basal part.