Photoprotection by photoinhibitory and PSII-reaction centre quenching controls growth of Ulva rigida (Chlorophyta) and is a pre-requisite for green tide formation.

MAIN CONCLUSION: The combined photoinhibitory and PSII-reaction centre quenching against light stress is an important mechanism that allows the green macroalga Ulva rigida to proliferate and form green tides in coastal ecosystems. Eutrophication of coastal ecosystems often stimulates massive and uncontrolled growth of green macroalgae, causing serious ecological problems. These green tides are frequently exposed to light intensities that can reduce their growth via the production of reactive oxygen species (ROS). To understand the physiological and biochemical mechanisms leading to the formation and maintenance of green tides, the interaction between inorganic nitrogen (Ni) and light was studied. In a bi-factorial physiological experiment simulating eutrophication under different light levels, the bloom-forming green macroalga Ulva rigida was exposed to a combination of ecologically relevant nitrate concentrations (3.8-44.7 µM) and light intensities (50-1100 µmol photons m-2 s-1) over three days. Although artificial eutrophication (≥ 21.7 µM) stimulated nitrate reductase activity, which regulated both nitrate uptake and vacuolar storage by a feedback mechanism, nitrogen assimilation remained constant. Growth was solely controlled by the light intensity because U. rigida was Ni-replete under oligotrophic conditions (3.8 µM), which requires an effective photoprotective mechanism. Fast declining Fv/Fm and non-photochemical quenching (NPQ) under excess light indicate that the combined photoinhibitory and PSII-reaction centre quenching avoided ROS production effectively. Thus, these mechanisms seem to be key to maintaining high photosynthetic activities and growth rates without producing ROS. Nevertheless, these photoprotective mechanisms allowed U. rigida to thrive under the contrasting experimental conditions with high daily growth rates (12-20%). This study helps understand the physiological mechanisms facilitating the formation and persistence of ecologically problematic green tides in coastal areas.

Ulvans are not equal - Linkage and substitution patterns in ulvan polysaccharides differ with Ulva morphology.

Ulva are hardy green seaweeds that contain the sulfated polysaccharide ulvan and grow in two distinct morphologies: foliose and tubular. The authors hypothesise that ulvan from tubular species are more structurally complex than ulvans from foliose species. Herein, using standardised methods, the glycosyl linkage positions and sulfate ester substitutions of constituent monosaccharides of ulvan isolated from foliose (U. lacinulata and U. stenophylloides) and tubular (U. prolifera and U. ralfsii) species of Ulva were investigated. Comparison of native ulvans with 80 and 100 °C desulfated counterparts indicated that 4-linked rhamnose is predominantly 3-O-sulfated in all four ulvans. Ulvans from the foliose species predominantly contained →3,4)-Rhap-(1→, →4)-GlcAp-(1→ and →4)-IdoAp-(1→, collectively accounting for 67 to 81 mol% of the total linkages. In contrast, these same linkages in ulvans from the tubular species only collectively accounted for 29 to 36 mol%. Instead, ulvan from tubular species contained a combination of →2,3,4)-Rhap-(1→, terminal Rhap-(1→, →4)-GlcAp-(1→, →4)-Xylp-(1→, and/or →4)-Galp-(1→ in high proportions; some of the latter three residues were also likely O-2 sulfated. The results presented here suggest that ulvan from foliose species are predominantly unbranched polysaccharides composed of repeat disaccharides while ulvans from tubular species contain a greater diversity of branch and sulfate substitution locations.

Fabrication of carbon black nanoparticles from green algae and sugarcane bagasse.

There are several industrial uses for carbon black (CB), an extremely fine powdered form of elemental carbon that is made up of coalesced particle aggregates and almost spherical colloidal particles. Most carbon black is produced from petroleum-derived feedstock, so there is a need to find an alternative method to produce CB, which relies on renewable resources such as algae and agricultural waste. A process involving hydrolysis, carbonization, and pyrolysis of green algae and sugarcane bagasse was developed, as the optimal hydrolysis conditions (16N sulfuric acid, 70 °C, 1 h, 1:30 g/ml GA or SC to sulfuric acid ratio), a hydrolysis ratio of 62% for SC and 85% for GA were achieved. The acidic solution was carbonized using a water bath, and the solid carbon was then further pyrolyzed at 900 °C. The obtained carbon black has a high carbon content of about 90% which is confirmed by EDX, XRD, and XPS analysis. By comparison carbon black from sugar cane bagasse (CBB) and carbon black from green algae Ulva lactuca (CBG) with commercial carbon black (CCB) it showed the same morphology which was confirmed by SEM analysis. The BET data, showed the high specific surface area of prepared CB, which was 605 (m2/g) for CBB and 424 (m2/g) for CBG compared with commercial carbon black (CBB) was 50 (m2/g), also the mean pore diameter of CBB, CBG and CCB indicated that CBB and CBG were rich in micropores, but CCB was rich in mesoporous according to IUPAC classification. This study might have created a technique that can be used to make carbon black from different kinds of biomass.

Biomonitoring of microplastics, anthropogenic microfibres and glass retroreflective beads by marine macroalgae.

Microplastics and other microscopic debris are a concern in the coastal environment but measurements in the water column and sediment are often problematic and rely on non-standardised and highly variable methodologies. To this end, we explore the potential of different species of temperate-cold marine macroalgae as passive biomonitors of anthropogenic microparticles at three contrasting locations in southwest England. Specifically, fronds from samples of fucoids and Ulva lactuca (n = 9 in total, and three from each location) have been sectioned and analysed directly under a microscope and anthropogenic microparticles counted and subsequently characterised for chemical composition. Microparticles were heterogeneously distributed throughout sections from the same sample. However, on a dry weight basis, combined microparticle concentrations for each sample ranged from about 7.5 g-1 to 110 g-1, and from about 0.2 cm-2 to 0.9 cm-2, and for a given species were higher in samples from a semi-enclosed harbour and urban beach than in samples from a protected beach facing the open sea. These values compare with published concentrations of microplastics and microfibres reported for the regional water column on the order of 0.1 m-3. Most particles were cellulosic (e.g., rayon) and petroleum-based (mainly polyester and polyethylene terephthalate) fibres but plastic fragments were also present on most samples. Glass retroreflective beads derived from road markings were also present at up to 18 g-1 on fucoids from the urban beach because of its proximity to a stormwater effluent. Most microparticles were adhered to the smooth parts of the macroalgal surface but some displayed wrapping around edges and creases or entrapment by appendages. The practical and environmental implications of macroalgae passively capturing significant quantities of anthropogenic microparticles are discussed.

Effects of photoperiod on the growth and physiological responses in Ulva prolifera under constant and diurnal temperature difference conditions.

Photoperiod and temperature are two main factors in the growth of macroalgae, and changes in photoperiod and diurnal temperature difference exist in natural condition. In order to study the effects of photoperiod and diurnal temperature difference on the growth of green algae Ulva prolifera, we cultured this species under three light/dark cycles (light: dark = 10:14, 12:12 and 16:08) with constant (22 °C for light and dark period, noted as 22-22 °C) and diurnal temperature difference (22 °C and 16 °C for light and dark period, respectively, noted as 22-16 °C) conditions. The results showed that: 1) Compared with 10:14 light/dark cycle, the growth of U. prolifera under 12:12 light/dark cycle was significantly enhanced by 39% and 16% for 22-22 °C and 22-16 °C treatments, respectively, while the increase proportion decreased when the daylength increase from 12 h to 16 h. 2) The enhancement in growth induced by diurnal temperature difference was observed under 10:14 light/dark cycle, but not for 12:12 and 16:08 light/dark cycle treatments. 3) The Chl a content and photosynthetic rate increased under short light period and 22-22 °C conditions, while under 22-16 °C conditions, higher photosynthetic rate was observed under 12:12 light/dark cycle and no significant difference in Chl a content was observed. 4) Under 22-22 °C conditions, compared with 10:14 (L:D) treatment, the expression levels of proteins in light-harvesting complexes, PSII and carbon fixation were down regulated, while the photorespiration and pentose phosphate pathway (PPP) were up regulated by 16:08 light dark cycle. Then we speculate that the higher photosynthetic rate may be one compensation mechanism in short photoperiod, and under long light period condition the up regulations of photorespiration and PPP can be in charge of the decrease in enhancement growth induced by longer daylength.

Bioaccessibility of toxic heavy metals/metalloids in edible seaweeds: Exposure and health risk assessment.

This study assesses the health risk due to heavy metals/metalloids (HMs/Ms) in edible seaweeds (Caulerpa racemosa, Kappaphycus alvarezii, and Ulva lactuca) through an in vitro bioaccessibility study. The percentage of bioabsorbed HMs/Ms in unprocessed and processed C. racemosa, U. lactuca, and K. alvarezii ranged from 3 % to 46 %, 3 % to 42 %, and 3 % to 40 %, respectively. The levels of HMs/Ms in seawater, sediment, and seaweeds were below the levels recommended by the European Commission (EC) and World Health Organization/Food and Agriculture Organization (WHO/FAO). The maximum accumulation of HMs/Ms was found during monsoons and post-monsoon seasons, and Cd, Pb, Hg, Cr, As, and Pb were predominant in all the samples. Tukey's post hoc test and t-test confirmed that thermal processing significantly reduced HMs/Ms in seaweeds. On the basis of the bioabsorption of HMs/Ms, the TTHQ values were found to be < 1, and the LCR values were within the acceptable limit (10-06 to 10-04), indicating no carcinogenic risks through seaweeds.

Composition and nutritional values of fatty acids in marine organisms by one-step microwave-assisted extraction/derivatization and comprehensive two-dimensional gas chromatography -flame ionization detector.

This work reports the characterization of the lipidic fraction of seven species of marine organisms gathered along the shoreline of the Po Delta Park of Emilia-Romagna Region (Italy) and of the north Adriatic Sea. Two species of oysters (Crassostrea gigas and Ostrea edulis), two species of clams (Chamelea gallina and Ruditapes philippinarum), one species of mussel (Mytilus galloprovincialis), one species of macroalgae (Ulva rigida), and one species of spiny dogfish (Squalus acanthias) were analyzed to characterize their fatty acids profile and related nutritional value. The lipid fraction was simultaneously extracted and transesterified into fatty acid methyl esters (FAMEs) by using a recently developed one-step microwave-assisted extraction/derivatization (MAED) method. The obtained FAMEs extract was analyzed by a rapid comprehensive multidimensional gas chromatography (GC × GC) method (30 min). The system was equipped with a reverse set of columns (polar × non-polar) connected through a reversed fill/flush flow modulator. The GC × GC system was coupled with a flame-ionization detector (FID) for both qualitative and quantitative purposes. The MAED- GC × GC-FID methodology was suitable in the context of samples containing high percentages of omega-3 PUFA. A total of 82 FAMEs were tentatively identified using standards, literature data, and the two-dimensional plot location. FAME profiles obtained with the proposed approach were comparable with reference methods (AOCS Ce 2b-11), showing no significant differences. Moreover, to determine the food nutritional value of the samples investigated, the most common nutritional indices (index of atherogenicity, index thrombogenicity, hypocholesterolemic/hypercholesterolemic ratio, health-promoting index, unsaturation index, and the fish lipid quality index) were calculated from FAME profiles. Among the samples investigated, Squalus acanthias presented the best nutritional score, while Ruditapes philippinarum had the worst score in 3 out of 6 indices.

A new approach to explore and assess the sustainable remediation of chromium-contaminated wastewater by biochar based on 3E model.

As a cost-effective material, biochar, known as 'black gold', has been widely used for environmental applications (EA), including chromium-contaminated wastewater remediation. However, limited reports focused on the multiple impacts of biochar, including energy consumption (EC) and environmental risk (ER). Hence, to recommend biochar as a green material for sustainable development, the three critical units were explored and quantitatively assessed based on an adapted 3E model (EA-EC-ER). The tested biochar was produced by limited-oxygen pyrolysis at 400-700 °C by using three typical biomasses (Ulva prolifera, phoenix tree, and municipal sludge), and the optimal operational modulus of the 3E model was identified using six key indicators. The findings revealed a significant positive correlation between EC and biochar yield (p < 0.05). The biochar produced by phoenix tree consumed more energy due to having higher content of unstable carbon fractions. Further, high-temperature and low-temperature biochar demonstrated different chromium removal mechanisms. Notably, the biochar produced at low temperature (400 °C) achieved better EA due to having high removal capacity and stability. Regarding ER, pyrolysis temperature of 500 °C could effectively stabilize the ecological risk in all biochar and the biochar produced by Ulva prolifera depicted the greatest reduction (37-fold). However, the increase in pyrolysis temperature would lead to an increase in global warming potential by nearly 22 times. Finally, the 3E model disclosed that the biochar produced by Ulva prolifera at 500 °C with low EC, high EA, and low ER had the most positive recommendation index (+78%). Importantly, a rapid assessment methodology was established by extracting parameters from the correlation. Based on this methodology, about eight percent of biochar can be the highest recommended from more than 100 collected peer-related data. Overall, the obtained findings highlighted that the multiple impacts of biochar should be considered to efficiently advance global sustainable development goals.

Characterization and Biological Activities of the Ulvan Polysaccharide-Rich Fraction Obtained from Ulva rigida and Ulva pseudorotundata and Their Potential for Pharmaceutical Application.

Seaweed from the genus Ulva (Ulvales, Chlorophyta) has a worldwide distribution and represents a potential biomass source for biotechnological applications. In the present study, we investigated the ulvan polysaccharide-rich fraction (UPRF) isolated from two Ulva species (U. rigida and U. pseudorotundata), naturally occurring on the Spanish Mediterranean coast. Chemical characterization of UPRFs was performed in order to explore the polysaccharides' composition. Biological assessments of UPRFs were compared by antioxidant activity and in vitro toxicity tests in the human cell lines: HCT-116 (colon cancer), G-361 (malignant melanoma), U-937 (leukemia), and HaCaT cells (immortalized keratinocytes). Chemical analysis revealed that both UPRFs presented rhamnose as the major relative sugar constituent, followed by glucose in U. rigida and xylose in U. pseudorotundata. Both also presented glucuronic acid, galactose, ribose, and mannose as the remaining monosaccharides. Similar antioxidant activity was obtained, where we observed increased activity in response to increased polysaccharide concentrations. Both UPRFs presented moderate toxicity against HCT-116 cell lines and a selectivity index ≥ 3, suggesting a good potential for use in pharmaceutical products.

Overwintering and summer survival of Ulva prolifera in sediments: Indoor simulation of temperature impacts.

Green tides, a globally prevalent marine ecological anomaly observed in coastal regions, have received substantial attention. However, there is limited research on the burial of Ulva prolifera in sediments during the late stages of green tide outbreaks. This study investigates the effect of temperature on U. prolifera buried in sediment over 30 days. The measurements included the length, biomass, relative growth rate, chlorophyll composition and maximum quantum yield (Fv/Fm) of PS II at different stages. The results indicate that at -20 °C, numerous seedlings emerged after 14 days of recovery culture, suggesting the release of spores or gametes; survival was possible from -2 °C to 15 °C; but at 20 °C and 30 °C, all U. prolifera died. The U. prolifera buried in sediment during the late stage of green tide outbreaks may serve as one of the sources for the subsequent year's green tide eruption. This research provides insights into the origins of green tide outbreaks in the southern Yellow Sea.

Modelling bioremediation of contaminated effluents by Ulva ohnoi. - A predictive perspective.

Ulva spp. are tolerant to salinity variations and exhibit easy acclimation, playing an essential role in the depollution of aquatic ecosystems precisely due to their high efficiency in absorbing and accumulating nutrients. For this reason, Ulva spp. becomes an attractive solution for recovering areas that suffer the impacts of problems such as the eutrophication of anthropogenic origin. In addition to being a promising alternative for the blue bioeconomy, it can contribute to the sustainability of economic activities in coastal areas. Therefore, the present study aimed to develop and elucidate the behavior of Ulva ohnoi using predictive surface response models. The algae were grown under different concentrations of nutrient and salinity levels, as predicted by the experimental design, and it was evaluated according to the potential of the biomass to absorb the nutrients, as well as its photosynthetic performance and biochemical parameters. Our study confirmed the high efficiency and preference of Ulva ohnoi in the absorption of nitrogen dissolved in the medium in the form of NH4+ and that salinity is an essential factor in the dynamics and speed of ammonium absorption. The absorption of orthophosphate by U. ohnoi is reverted to the culture medium when subjected to long-term cultivation. This process was more intense because of low salinity, even at conditions of availability of the compound. The 3D-models of response surfaces elucidate the behavior of Ulva ohnoi, attributing a correlation between nutrient availability and salinity and the biological behavior of the species. In view of what is exposed by these models, as well as the effects of saline distribution along the Lagoon, the following regions of the lagoon are suggested: Center-North, Center and South - as potential areas for the implementation of bioremediation projects with Ulva ohnoi.

Integrated transcriptomics and proteomics analysis reveals muscle metabolism effects of dietary Ulva lactuca and ulvan lyase supplementation in weaned piglets.

Seaweeds, including the green Ulva lactuca, can potentially reduce competition between feed, food, and fuel. They can also contribute to the improved development of weaned piglets. However, their indigestible polysaccharides of the cell wall pose a challenge. This can be addressed through carbohydrase supplementation, such as the recombinant ulvan lyase. The objective of our study was to assess the muscle metabolism of weaned piglets fed with 7% U. lactuca and 0.01% ulvan lyase supplementation, using an integrated transcriptomics (RNA-seq) and proteomics (LC-MS) approach. Feeding piglets with seaweed and enzyme supplementation resulted in reduced macronutrient availability, leading to protein degradation through the proteasome (PSMD2), with resulting amino acids being utilized as an energy source (GOT2, IDH3B). Moreover, mineral element accumulation may have contributed to increased oxidative stress, evident from elevated levels of antioxidant proteins like catalase, as a response to maintaining tissue homeostasis. The upregulation of the gene AQP7, associated with the osmotic stress response, further supports these findings. Consequently, an increase in chaperone activity, including HSP90, was required to repair damaged proteins. Our results suggest that enzymatic supplementation may exacerbate the effects observed from feeding U. lactuca alone, potentially due to side effects of cell wall degradation during digestion.

A refined deep-learning-based algorithm for harmful-algal-bloom remote-sensing recognition using Noctiluca scintillans algal bloom as an example.

Harmful algal blooms (HABs) are challenging to recognize because of their striped and uneven biomass distributions. To address this issue, a refined deep-learning algorithm termed HAB-Ne was developed for the recognition of HABs in GF-1 Wide Field of View (WFV) images using Noctiluca scintillans algal bloom as an example. First, a pretrained image super-resolution model was integrated to improve the spatial resolution of the GF-1 WFV images and minimize the impact of mixed pixels caused by the strip distribution. Side-window convolution was also explored to enhance the edge features of HABs and minimize the effects of uneven biomass distribution. In addition, a convolutional encoder-decoder network was constructed for threshold-free HAB recognition to address the dependence on thresholds in existing methods. HAB-Net effectively recognized HABs from GF-1 WFV images, achieving an average precision of 90.1% and an F1-score of 0.86. HAB-Net showed more fine-grained recognition results than those of existing methods, with over 4% improvement in the F1-Score, especially in the marginal areas of HAB distribution. The algorithm demonstrated its effectiveness in recognizing HABs in different marine environments, such as the Yellow Sea, East China Sea, and northern Vietnam. Additionally, the algorithm was proven suitable for detecting the macroalga Sargassum. This study demonstrates the potential of deep-learning-based fine-grained recognition of HABs, which can be extended to the recognition of other fine-scale and strip-distributed objects, such as oil spills and Ulva prolifera.

Exposure to trace levels of live seaweed-derived antibacterial 2,4,6-tribromophenol modulates ß-lactam antibiotics resistance in Vibrio.

Non-antibiotic substances have been found to contribute to the spread of antibiotic resistance. Bromophenols (BPs) are special anti-bacterial substances obtained from seaweed. This study explored the modulatory effect of trace BPs from a live seaweed on the antibiotic resistance of pathogenic Vibrio (V.) strains. A hydroponic solution of Ulva fasciata was found to contain trace levels (9-333 µg L-1) of 2,4,6-tribromophenol (TBP), a typical BP. TBP at a concentration of 165 µg L-1 significantly increased the inhibition zone diameter of widely used ß-lactam antibiotics (amoxicillin and ampicillin) against V. alginolyticus M7 (Va. M7) and V. parahaemolyticus M3 (Vp. M3) as well as reduced the minimum inhibitory concentration by 2-4 fold against Va. M7. Whole genome re-sequencing analysis demonstrated that Va. M3 (53-60) had more mutant genes than Vp. M7 (44) in ß-lactam resistance pathway. Transcriptome sequencing analysis, along with verification through RT-qPCR, further showed that oligopeptide permease (opp) was the only differentially expressed gene (DEG) among the mutated genes in the ß-lactam resistance pathway. The opp transport activity and membrane permeability of Vibrio were both enhanced at 165 µg L-1 of TBP, and the ability of biofilm formation was also decreased. Thus, antibiotics resistance improvement of Vibrio by TBP was potentially related with the promoted opp transport activity, membrane permeability and inhibited biofilm formation.

The protective effect of Enteromorpha prolifera polysaccharide on alcoholic liver injury in C57BL/6 mice.

An alcohol-induced liver injury model was induced in C57BL/6 mice to assess the protective efficacy of Enteromorpha prolifera polysaccharides (EP) against liver damage. Histological alterations in the liver were examined following hematoxylin-eosin (H&E) staining. Biochemical assay kits and ELISA kits were employed to analyze serum and liver biochemical parameters, as well as the activity of antioxidant enzymes and alcohol metabolism-related enzymes. The presence of oxidative stress-related proteins in the liver was detected using western blotting. Liquid chromatography and mass spectrometry were used to profile serum metabolites in mice. The findings demonstrated that EP-H (100 mg/Kg) reduced serum ALT and AST activity by 2.31-fold and 2.32-fold, respectively, when compared to the alcohol-induced liver injury group. H&E staining revealed a significant attenuation of microvesicular steatosis and ballooning pathology in the EP-H group compared to the model group. EP administration was found to enhance alcohol metabolism by regulating metabolite-related enzymes (ADH and ALDH) and decreasing CYP2E1 expression. EP also modulated the Nrf2/HO-1 signaling pathway to bolster hepatic antioxidant capacity. Furthermore, EP restored the levels of lipid metabolites (Glycine, Butanoyl-CoA, and Acetyl-CoA) to normalcy. In summary, EP confers protection to the liver through the regulation of antioxidant activity and lipid metabolites in the murine liver.

Flash extraction of ulvan polysaccharides from marine green macroalga Ulva linza and evaluation of its antioxidant and gut microbiota modulation activities.

In this study, flash extraction was used to rapidly extract water-soluble polysaccharides from Ulva linza. The optimal extraction process for the flash extraction was determined by Box-Behnken design with extraction temperature 80 °C, extraction time 117 s, liquid-solid ratio 46:1 (mL/g) and a corresponding yield of 18.5 %. The crude Ulva linza polysaccharides (CULP) were subsequently isolated by chromatography technology to obtain purified Ulva linza polysaccharide (ULP) and characterized by monosaccharide composition and molecular weight determination analysis. Furthermore, the antioxidant bioactivity of ULP was studied and the results revealed that it had a good scavenging effect on DPPH, ABTS and OH, with IC50 values of 149.2 µg/mL, 252.5 µg/mL and 1073 µg/mL, respectively. After in vitro fermentation by human fecal microbiota, the pH value of fermentation culture significantly decreased to 5.06, suggesting that ULP could be hydrolyzed and utilized by gut microbiota. The abundance of beneficial bacteria including Bacteroides, Parabacteroides and Faecalibacterium was improved. Meanwhile, the relative abundance of Prevotella, Blautia and Ruminococcus was decreased, and the low ratio of these organisms might reveal positive effects on maintaining the balance of gut microbial biodiversity. These results suggested that the composition of the human gut microbiota could be modulated by ULP, and ULP might possess the potential to maintain gut homeostasis and improve human intestinal health.

Synergistic activity of Limosilactobacillus reuteri KUB-AC5 and water-based plants against Salmonella challenge in a human in vitro gut model.

A synbiotic is a combination of live microorganisms and specific substrates that are selectively utilized by host microorganisms, resulting in health benefits for the host. Previous studies have demonstrated the protective effects of L. reuteri KUB-AC5 against Salmonella infection in chicken and mouse models. The probiotic activity of L. reuteri KUB-AC5 in these hosts was influenced by nutritional supplements. Water-based plants contain significant amounts of carbohydrates, particularly dietary fiber and proteins, making them potential prebiotic substrates. In this study, four water-based plants (Ulva rigida, Caulerpa lentillifera, Wolffia globosa, and Gracillaria fisheri) were screened for their ability to support the growth of L. reuteri KUB-AC5. Under monoculture testing, U. rigida exhibited the highest capacity to support the growth of L. reuteri KUB-AC5 and the production of organic acids, including acetic acid, lactic acid, and propionic acid (p ≤ 0.05). In co-culture experiments, the synbiotic combination of U. rigida and L. reuteri KUB-AC5 demonstrated the potential to eliminate Salmonella Typhimurium DMST 48437 when inoculated at 104 CFU/mL within 9 h. The synbiotic activities of U. rigida and L. reuteri KUB-AC5 were further investigated using an in vitro human gut model. Compared to the probiotic treatment, the synbiotic combination of L. reuteri KUB-AC5 and U. rigida showed significantly higher levels of L. reuteri KUB-AC5 (5.1 log copies/mL) and a reduction of S. Typhimurium by 0.8 log (CFU/ml) after 24 h (p ≤ 0.05). Synbiotic treatment also significantly promoted the production of short-chain fatty acids (SCFAs), including butyric acid, propionic acid, and acetic acid, compared to prebiotic and probiotic treatments alone (p ≤ 0.05). Furthermore, the synbiotic formulation modulated the in vitro simulated gut microbiome, enhancing putatively beneficial gut microbes, including lactobacilli, Faecalibacterium, and Blautia. Our findings demonstrated that L. reuteri KUB-AC5, in combination with U. rigida, exhibited synergistic activity, as indicated by increased viability, higher anti-pathogenicity toward Salmonella, and the ability to modulate the gut microbiome.

Acclimation of intertidal macroalgae Ulva prolifera to UVB radiation: the important role of alternative oxidase.

BACKGROUND: Solar radiation is primarily composed of ultraviolet radiation (UVR, 200 - 400 nm) and photosynthetically active radiation (PAR, 400 - 700 nm). Ultraviolet-B (UVB) radiation accounts for only a small proportion of sunlight, and it is the primary cause of plant photodamage. The use of chlorofluorocarbons (CFCs) as refrigerants caused serious ozone depletion in the 1980s, and this had led to an increase in UVB. Although CFC emissions have significantly decreased in recent years, UVB radiation still remains at a high intensity. UVB radiation increase is an important factor that influences plant physiological processes. Ulva prolifera, a type of macroalga found in the intertidal zone, is intermittently exposed to UVB. Alternative oxidase (AOX) plays an important role in plants under stresses. This research examines the changes in AOX activity and the relationships among AOX, photosynthesis, and reactive oxygen species (ROS) homeostasis in U. prolifera under changes in UVB and photosynthetically active radiation (PAR). RESULTS: UVB was the main component of solar radiation impacting the typical intertidal green macroalgae U. prolifera. AOX was found to be important during the process of photosynthesis optimization of U. prolifera due to a synergistic effect with non-photochemical quenching (NPQ) under UVB radiation. AOX and glycolate oxidase (GO) worked together to achieve NADPH homeostasis to achieve photosynthesis optimization under changes in PAR + UVB. The synergism of AOX with superoxide dismutase (SOD) and catalase (CAT) was important during the process of ROS homeostasis under PAR + UVB. CONCLUSIONS: AOX plays an important role in the process of photosynthesis optimization and ROS homeostasis in U. prolifera under UVB radiation. This study provides further insights into the response of intertidal macroalgae to solar light changes.

A new set of N isotopic reference values for monitoring Ulva green tides in coral reef ecosystems.

Green tides occurrence has increased in coral reefs, yet few reference values have been documented to support bloom management in these ecosystems. Here, we took advantage of recent Ulva green tides that occurred in New Caledonia to (i) identify the elements limiting the growth of Ulva spp. during these blooms; and (ii) validate the use of isotopic markers for identifying sources of nutrients that generated blooms. N/P ratios highlighted a stronger limitation of algae by phosphorus than by nitrogen on sites under oceanic influence, while the proportions of N and P were optimal for algal growth at sites where green tides occurred. Macroalgae highly exposed to sewage water was characterized by higher δ15N than macroalgae collected in areas exposed to synthetic inorganic fertilizers. From these results, we established a new set of threshold values for using δ15N in Ulva species as an indicator of nitrogen source type in coral reefs.

Enantioselective Total Synthesis of the Morphogen (-)-Thallusin and Mediated Uptake of Fe(III) into the Green Seaweed Ulva.

A fully enantioselective, catalytic synthesis of the algal morphogen (-)-thallusin using polyene cyclization chemistry is reported. The synthesis features dedicated precursor design, introduction of a TMS-substituted arene as a regioselective terminator, very high enantiomer excess (ee) on gram scale, and productive scaffold functionalization. Furthermore, an ee determination methodology of thallusin samples was developed, and the ee of biosynthesized thallusin was determined. Fe(III)-uptake studies demonstrated that the cellular uptake of iron facilitated by thallusin derivatives was independent of their morphogenic activity, suggesting their active import via siderophore transporters as a shuttle system.