Red Algae Research Articles

Silver nanoparticles synthesized from marine algae Spatoglossum asperum: Antioxidant properties and seed germination enhancement

Biosynthesized silver nanoparticles (AgNPs) have shown promising potential in plant growth under stressed conditions but marine algae synthesized AgNPs still remain least explored. In the current study, AgNPs have been synthesis by using the aqueous extract of marine brown alga Spatoglossum asperum as a reducing medium and their application in the growth of Vigna radiata seeds under salt stress conditions was studied. The antioxidant potential of AgNPs in comparison with algal extract was also assessed. The AgNPs synthesized using the algal extract was characterized by means of UV–Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray (XRD) diffraction analysis, Field emission scanning electron microscopy (FE-SEM) and Energy dispersive X-ray spectroscopy (EDS). The FE-SEM and EDS results confirmed the formation of multi-shaped (spherical, cubical and nano-clusters) particles with average size of 43.65 nm. Developed AgNPs showed a surface plasmon resonance band at 425 nm and a face-centric cubic crystallographic structure with an average crystallite size of 23.05 nm. The FTIR spectrum ensured the involvement of di and polysulphides in the synthesis of nanoparticles. The results revealed that the algal synthesized AgNPs showed superior antioxidant activity compared to the algal extract alone and significantly enhanced seed germination in Vigna radiata under both normal and saline conditions. These findings suggest that Spatoglossum asperum derived AgNPs could play a pivotal role in agriculture and environmental sustainability.

Exploration of the extracellular matrix of the red alga Chondrus crispus reveals unprecedented insights into carrageenan structures

Carrageenans are major gel forming polysaccharides in the extracellular matrix of the red macroalga Chondrus crispus. These galactans are made of linear chains of repetitive disaccharide motifs based on d-galactose residues alternately linked by β-1,4 and α-1,3 glycosidic bonds. A definite number of disaccharide motifs are known, based on their regular sulfations and the presence of a 3,6-anhydro bridge. While these motifs are variable as a function of species, life cycle phases, or seasons, our understanding of the in vivo regulation of carrageenan fine structures is still limited. Characterized hydrolytic enzymes (κ-, ι- and λ-carrageenases) are powerful tools for identifying glycan structures in extracted ECMs. Their use, combined to chromatography and high-resolution mass spectrometry, allowed us to refine our understanding of carrageenan variability in the phases of C. crispus. We provide the first demonstration that κ/ι carrabiose motifs are not limited to gametophytes, but are also present in tetrasporophytes, together with over- and under-sulfated λ-motifs. Our findings highlight a more complex carrageenan composition than previously described in this model system. These results are further discussed in the light of recent transcriptomic data and suggest that the historical hypotheses on the biosynthetic pathway of carrageenans in red algae may need revision. HypothesisCombined characterized hydrolytic enzymes to chromatography and high-resolution mass spectrometry can refine our understanding of carrageenan variability in the phases of C. crispus.

Diversity and paleoecological significance of zooxanthellate corals of Oligocene Qom Formation, SE Iran

Zooxanthellate corals are Iran's most abundant macrofossils in the Oligocene-early Miocene Qom Formation deposits in the NE margin of the Tethyan Seaway. Yet, basic knowledge about the diversity of these organisms and their paleoecology is still scarce. This paper uses late Rupelian–Chattian coral data from three exposed sections in the northwestern Jazmurian Lake, SE Iran, as the southeasternmost outcrops of the Qom Formation, are analyzed in terms of diversity and paleoecology. The coralline red algae and larger benthic foraminiferal assemblages associated with the corals have also been used to infer the paleoenvironmental and paleoecological conditions. The following coral genera were recognized: Leptoria, Caulastraea, Hydnophora, Astreopora, Plesiastrea, Thegioastraea, Porites, Goniopora, Platycoenia, Acropora, Tarbellastraea, Favites, Heliastraea, Stylocoenia, Ceratotrochus. The high abundance of z-corals, larger benthic foraminifera (LBF), and coralline red algae demonstrate that the deposition took place in tropical-subtropical warm waters mainly within the euphotic to the mesophotic zones. The presence of various coral fabrics including pillarstone, domestone, and rudstone allowed to infer high to moderate hydrodynamic energy in the studied sections. As well, given the interactions among corals, filter-feeders, green and red algae, bioeroders, and the surrounding environment, it seems that oligotrophic to slightly mesotrophic conditions also had prevailed in the studied area.

Biostimulators with marine algae extracts and their role in increasing tolerance to drought stress in highbush blueberry cultivation

Drought is one of the most serious challenges facing agriculture and ecosystems around the world. With more frequent and more extreme weather events, the effects of drought are becoming more severe, leading to yield losses, soil depletion and environmental degradation. In this work, we present an analysis of the impact of a marine algae biostimulanat andits ability to offset the effects of drought stress in blueberry cultivation. The aim of the research was to evaluate various fertilisation programs in increasing plant resistance to abiotic stress such as drought. It was tested whether the algal biostimulator provides the same tolerance to drought stress in highbush blueberry plants as regular fertilisers without biostimulation. The research was conducted in 2022 in a greenhouse in controlled drought conditions. Three-year-old highbush blueberry bushes (12 pieces) were used in the experiment. Highbush blueberry bushes (Vaccinium corymbosum) ’Brigitta Blue’ varieties were planted in plastic pots with a capacity of 10 dm3 containing an acidic substrate and placed in a greenhouse. Controlled lighting conditions were maintained using sodium lamps and a temperature of 25°C/20°C day/night. The substrate in pots was maintained at 80% of field water capacity by manual watering and weekly supply of nutrient solution for 5 weeks until water deficit occurred. Half of the plants were sprayed weekly with biostimulant at a concentration of 1%, three times 1 week apart (1 application per week). The biostimulant was evenly applied to the entire plant. Seven days after the third application of the product, half of the unsprayed and sprayed plants were subjected to water deficit stress by holding thewatering until 40% of the field water capacity (FC) was reached. The experimental layout included four combinations: C—Control—no biostimulation, no water deficit; CS—Stress control—water deficit up to 40% FC, no biostimulation; B—Biostimulator—no water deficit, biostimulation; BS—Stress plus biostimulator—water deficit up to 40% FC, biostimulation. Fertilisers with seaweed extracts show the ability to reduce the adverse effects of stress, promoting plant resilience, including tolerance to drought stress. The following were evaluated in the experiment: catalase activity, peroxidase activity, free malondialdehyde content, photosynthetic activity and leaf mineral content. The biostimulant used in experiment increased the oxidative activity of the enzymes pe-roxidase and catalase under simulated drought stress conditions. The algal biostimulant increased the average value of catalase activity by 20% in comparison to the control plants, in both combinatinations. The tested biostimulator had no effect on the chlorophyll content in the leaves or the concentration of nutrients in the leaves. The effect of marine algae products on the yield quantity and high quality is related among other to bioactive substances which helps to prevent drought stress.

Impact of Chaetomorpha aerea-enriched diet on growth, feed utilization, and haemato-immunological responses in Clarias batrachus challenged with Aeromonas hydrophila

The bacteria Aeromonas hydrophila, which causes motile Aeromonas septicemia (MAS), is dangerous to aquaculture because it affects the fish's well-being and production. As the aquaculture industry seeks sustainable and effective methods to enhance fish immunity and growth, natural supplements such as marine algae have gained attention. This study explored the potential benefits of incorporating the green marine algae Chaetomorpha aerea into the fish diet, focusing on disease resistance, growth, feed utilization, and hematological and immunological responses. Five diets were prepared, varying concentrations of C. aerea (0 control, T1: 1 g/kg; T2: 2 g/kg: T3: 5 g/kg: and T4: 10 g/kg) and administered to fish over 30 days. Following the feeding trial, the fish were exposed to A. hydrophila, and their survival rates were observed for the next 14 days. The findings demonstrated that the final weight, weight gain, relative growth rate, specific growth rate, and daily growth rate were all positively impacted by a diet containing 5 g/kg of C. aerea. Additionally, fish in the 5 g/kg C. aerea group demonstrated improved feed conversion efficiency compared to the control group. While there were no significant changes in red and white blood cell counts on the initial day, serum lysozyme activity and overall resistance to infection were enhanced in fish receiving C. aerea at 2 and 5 g/kg. These results imply that C. aerea supplementation with fish supplements may be a useful immunostimulant, boosting improved health and growth in sustainable aquaculture practices.

Assessment of Antioxidant and Hepatoprotective Effects of Kappaphycus alvarezii (Doty) Doty ex Silva Against Carbon Tetrachloride-Induced Liver Injury in Rats

Kappaphycus alvarezii (Doty) Doty ex Silva, commonly known as red algae, holds economic significance as a primary source of κ-carrageenan, which exhibits promising medicinal and therapeutic properties. This study aims to assess the antioxidant potential as well as hepatoprotective activity of the ethanolic extract of K. alvarezii (EEKA). The assays utilised to determine the antioxidant properties of EEKA were total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging. In addition, the ability of EEKA to ameliorate experimentally induced liver injury in Sprague-Dawley rats caused by carbon tetrachloride (CCl4) was evaluated. The biochemical assays involved measuring liver marker enzymes (AST and ALT) in serum as well as determining the levels of reduced glutathione (GSH), lipid peroxidation (LPO) via malondialdehyde, catalase (CAT), and glutathione S-transferase (GST) in liver homogenates. The TPC and DPPH radical scavenging activity of EEKA demonstrated relatively low antioxidant properties compared to standard references. However, CCl4-induced groups exhibited significantly increased levels of AST and ALT, along with depletion of antioxidant status (GSH, CAT, and GST) indicated by LPO. Pretreatment with EEKA resulted in slightly decreased liver marker enzyme activity and LPO, coupled with an increase in antioxidant status. These findings suggest that EEKA contains active principles capable of counteracting the hepatotoxic effects induced by CCl4.

Impact of marine algae extract and balanced fertilizer(NPK) on Hibicsus sabdariffa.L growth, quotient, and vitamin C content.

A field experiment was conducted in one of the experimental fields affiliated to Ibn Al-Bitar Vocational Preparatory School located in Al-Hussainiyah District - Karbala Governorate during the 2023 agricultural season with the aim of studying the impact of adding different concentrations of marine algae extract, balanced fertilizer in the growth qualities, yield and vitamin C in the roselle plant. The experiment was carried out according to a randomized complete block design (RCBD) with factorial arrangment and three replications. The experiment included two factors. The first factor included spraying with marine algae extract in concentrations ( 0, 0.25, 0.5 and 0.75 ml L-1) . The second factor included spraying with balanced fertilizer (NPK) in concentrations (0, 2.5 and 5 ml L-1). The results showed that spraying with marine algae extract (0.75 ml L-1) has a significant superiority in the vegetative growth qualities and vitamin C content of the roselle plant compared to other agile agreements, and the spraying with balanced fertilizer at a concentration of (5 ml L-1) It significantly excelled in all study indicators. The interaction between the two study factors, The spray treatment superiority (0.75 ml L-1) of algae extract with the of balanced fertilizer (5 ml L-1), and gave the highest averages for all the studied qualities., giving the highest Means for all the studied qualities.

Reinboldiella koreana sp. nov. (Ceramiales, Rhodophyta) is the correct name for the specimens previously known as Reinboldiella schmitziana in Korea

Epiphytic algae are important components of marine ecosystems. Despite the importance of epiphytic algae in marine ecosystems, our knowledge of these taxa is still limited. The marine red algal genus <i>Reinboldiella</i>, which is distributed mainly in the northwestern Pacific region, is characterized by tiny thalli that are epiphytic on various other red algae. Six species of the genus have been reported in Japan, Taiwan, and Korea. In this study, 50 Korean Reinboldiella specimens, previously known as <i>Reinboldiella schmitziana</i>, were collected from 11 localities and reexamined to verify their taxonomic status. We describe a new species, <i>Reinboldiella koreana</i> sp. nov., based on <i>rbc</i>L phylogeny and morphological observations. A total of four grateloupiacean species (<i>Pachymeniopsis lanceolata</i>, <i>P. elliptica</i>, <i>Grateloupia turuturu</i>, and <i>G. asiatica</i>) were identified as host species of <i>R. koreana</i> sp. nov. Due to the restricted host range of <i>R. koreana</i> sp. nov., a phylogenetic tree was reconstructed using the <i>cox</i>1 marker to confirm the co-phylogenetic relationships between the epiphytic algae and their grateloupiacean hosts. Two of the four cox1 haplotypes of <i>R. koreana</i> were found in different host species, regardless of which haplotype they were. It indicates that there are no co-phylogenetic relationships between <i>R. koreana</i> and host species.

Brown and red shades in the riverbed of the Nera River (Serbia) – update on the distribution and ecology of the association Hildenbrandio rivularis–Heribaudielletum fluviatilis Fritsch 1929 corr. Täuscher 2020 in Southeastern Europe

Heribaudiella fluviatilis (Areschoug) Svedelius is one of the rare representatives of freshwater brown algae, and its range is restricted to the Northern Hemisphere. Hildenbrandia rivularis (Liebmann) J. Agardh is still one of the endangered red algae species in Europe, although its indicator value and distribution have recently been questioned. The association Hildenbrandio rivularis– Heribaudielletum fluviatilis Fritsch 1929 corr. Täuscher 2020 occurs mainly in Northern and Central Europe, while its occurrence and ecology in Southern Europe are poorly researched. The lower reaches of the Nera River near the small town of Bela Crkva, Serbia, were searched for macroalgae in August 2021 and June 2022, when stones with macroalgal crusts were collected. Environmental parameters were measured in situ and water samples were collected for further analysis. A sample of the epilithic diatom community was collected to calculate diatom indices. We present the occurrence of the association Hildenbrandio rivularis–Heribaudielletum fluviatilis in the lower course of the Nera River in Serbia, relating the ecology of the species and habitat to previous findings from the Southeast European region. We discuss potential indicator values of macroalgae associations, rather than of a single species.

Grow with the flow: Is phenotypic plasticity across hydrodynamic gradients common in seaweeds?

Seaweeds are widely assumed to be phenotypically plastic across hydrodynamic gradients, yet while many marine macroalgae exhibit intraspecific phenotypic variation that correlates with flow, researchers often fail to test whether such variation is due to plasticity or another mechanism, such as local adaptation. In this minireview, we considered mechanisms for sensing flow in seaweeds that could facilitate adaptive phenotypic plasticity across hydrodynamic gradients. We then reviewed the literature from 1900 to 2024 to see how often phenotypic variation and plasticity across hydrodynamic gradients had been observed and demonstrated in different groups of seaweeds. In the last 124 years, phenotypic variation and plasticity in response to flow have been well documented in brown algae but scarcely documented in red and green algae. This could suggest that brown algae are better able to sense and respond to flow than red and green algae, perhaps due to the intercalary meristem of many brown algae, including most kelps. However, this skewed distribution could also be the result of publication bias, as most studies involving flow have been conducted on brown algae. Only 30% of 141 papers specifically investigated if observations of phenotypic variation along hydrodynamic gradients were due to plasticity. To date, phenotypic plasticity in response to flow has been demonstrated in 20 brown algal species, five red algal species, and two green algal species. Thus, the assumption that phenotypic plasticity to flow is common across seaweeds is not particularly well supported by the literature. Mechanisms underlying plasticity to flow are poorly understood and remain a critical avenue for future research.

Sporelings and growth of the marine red alga, Gelidium elegans (Gelidiaceae), from Northern Taiwan

Sporelings and growth of the marine red alga, Gelidium elegans (Gelidiaceae), from Northern Taiwan

60 Effects of a calcareous marine algae on dry matter intake, water intake, rumen temperature, rumen pH and average daily gain of grain-fed steers during a heat wave

Abstract During summer, feedlot cattle are often subjected to multiple high heat load events which can cause heat stress and negatively impact on cattle performance and well-being. The objective of this study was to evaluate the effects of different dietary buffering feeding strategies, on dry matter intake (DMI), water intake (WI), rumen temperature (TRUM), rumen pH and average daily gain (ADG) of grain-fed beef steers exposed to a simulated heat wave event. Angus steers [n = 12; body weight (BW) = 582 ± 8.92 kg] were housed within climate control rooms for 21 d and randomly allocated into one of three dietary treatments (4 steers/treatment): 1) Treatment 1 (T1), finisher diet; 2) Treatment 2 (T2), transitioned from finisher to heat load diet (HLD) on d 4 and fed HLD until d 16; 3) Treatment 3 (T3), fed finisher and supplemented with a calcareous marine algae (CMA; Acid Buffer, Celtic Sea Minerals) on d 4 until d 16. On d 17, T2 and T3 transitioned back to the finisher. Days were split into three phases consisting of i) d 0 to 6 [PI, Temperature Humidity Index (THI), THI 65-78]; ii) d 7 to 11 (PII, THI 83-87); iii) d 12 to 20 (PIII, THI 65-78). Data were analyzed using a repeated measures model, with a first order auto-regressive error structure, including fixed effects for treatment, phase, day and hour, with animal ID as a random effect. Body weight declined (P < 0.005) during PII, with steers losing on average, 17.65 ± 3.06 kg BW/steer (T1), 12.30 ± 3.06 kg BW/steer (T2) and 16.20 ± 3.06 kg BW/steer (T3) at conclusion of PII, with muscle atrophy visually evident (Table 1). There were no effects (P ≥ 0.93) for treatment on ADG. During PII, DMI decreased (P < 0.005), with T2 and T3 having >2kg DMIּ steer-1ּ d-1 greater (P ≤ 0.006) DMI compared with T1. During PIII, T1 maintained decreased (P ≤ 0.001) DMI compared with T2 and T3. During PII, mean WI increased (P ≤ 0.05) for T1 and T3, although remained unchanged (P = 0.11) for T2, TRUM increased (P < 0.0001), whilst range in TRUM decreased (P ≤ 0.01) for all TRT and rumen pH for T2 and T3 decreased (P ≤ 0.0003), whilst T1 tended (P ≥ 0.05) to decrease. Rumen pH diurnal rhythms were disrupted during PII, range in rumen pH also reduced (P < 0.0001) for T1 and T3, remaining unchanged (P = 0.94) for T2. Mean rumen pH was lower (P ≤ 0.002) during PIII compared with PI for all treatments. Both T2 and T3 had a lower (P ≤ 0.05) range in rumen pH than T1 during PIII. Data from the current study suggest that feeding strategies to include CMA may aide in moderating DMI reductions observed during and post-heat stress periods, whilst also reducing the range in rumen pH during post-heat wave conditions when rumen dysfunction challenges may present.

Gene editing of economic macroalga Neopyropia yezoensis (Rhodophyta) will promote its development into a model species of marine algae.

Gene editing of economic macroalga Neopyropia yezoensis (Rhodophyta) will promote its development into a model species of marine algae.

Temperature Dependence and the Effects of Ultraviolet Radiation on the Ultrastructure and Photosynthetic Activity of Carpospores in Sub-Antarctic Red Alga Iridaea cordata (Turner) Bory 1826.

The short-term effects of UV radiation and low temperature on ultrastructure, photosynthetic activity (measured as the maximal photochemical quantum yield of photosystem II: Fv/Fm), chlorophyll-a (Chl-a) contents, and UV-absorbing compounds on the carpospores of Iridaea cordata from a sub-Antarctic population were investigated. Exposure to both photosynthetically active radiation (PAR) and PAR + UV for 4 h caused ultrastructural modifications in all treatments. Under PAR + UV at 2 °C, a disruption of the chloroplast's internal organization was observed. Plastoglobuli were often found in carpospores exposed to 2 °C. 'Electron dense particles', resembling physodes of brown algae, were detected for the first time in cells exposed to PAR and PAR + UV at 8 °C. Fv/Fm decreased following 4 h exposure at 2 °C under PAR + UV (64%) and PAR (25%). At 8 °C, Fv/Fm declined by 21% only under PAR + UV. The photosynthesis of carpospores previously treated with UV partially recovered after a 4 h exposure under dim light. UV-absorbing compounds were degraded in all radiation and temperature treatments without recovery after a 4 h dim light period. Chl-a did not change, whereas total carotenoids increased under PAR at 8 °C The study indicates that although carpospores of I. cordata exhibit photoprotective mechanisms, UV radiation strongly damages their ultrastructure and physiology, which were exacerbated under low temperatures.

Meiosis I causes a high spontaneous mutation rate in a multicellular red alga (Pyropia yezoensis) with a complex life cycle

Mutations are the origin of genetic diversity and are fundamental parameters needed to understand the molecular evolution of species. Estimations of mutation rates have been conducted for many diverse taxa, although rates in several major eukaryotic lineages remain unexplored. Here, the first estimation is reported of the spontaneous mutation rate for the multicellular eukaryote red alga, Pyropia yezoensis, which exhibits a complex life cycle. An estimated mutation rate of 2.97 × 10−8 (95 % CI: 2.16 × 10−8–3.99 × 10−8) per site per generation was generated for the primary life cycle, the sexual cycle, which is the highest sexual mutation rate among published sexual plants. Combined with tetrad analysis, meiosis I was identified as the primary period responsible for the high mutation rate during the complex life cycle of P. yezoensis. This result provides direct evidence for the “meiosis is mutagenic” hypothesis for multicellular organisms. The accurate estimate of the mutation rate of P. yezoensis also informs several immediate applications. Based on the above estimate, the effective population size (Ne) of P. yezoensis was estimated at about 19,000, with extensive haploid phases and asexual reproduction through monospores possibly leading to linked selection that may reduce the genome-wide genetic diversity of P. yezoensis and consequently influence Ne estimation. Lastly, P. yezoensis was estimated to have diverged from P. haitanensis about 4.2 Ma, representing a more recent date than estimates from fossil-calibrated phylogenies. These findings provide valuable new information for understanding the evolution of red algae, in addition to the underlying mechanism of mutations.

Macroalgal Diseases: Exploring Biology, Pathogenesis, and Management Strategies

The global seaweed market is expected to reach USD 17.8 billion by 2032, fuelled by growing demand for sustainable and healthy food solutions and expanding applications in agriculture and aquaculture. However, this rapid growth poses significant challenges, particularly in managing diseases that often establish themselves in intensive macroalgal culture facilities. Red rot disease, Olpidiopsis, and green spot disease often affect marine macroalgae species of high commercial interest, as seen in Pyropia/Porphyra as has already happened for “ice-ice” malaise on Kappaphycus, causing huge economic losses. These diseases are caused by infectious agents that find their place in extreme environmental conditions, such as those characterized by sudden changes in temperature and pollution. Despite technological advances aimed at monitoring the well-being of cultivated seaweed, discrepancies between regions’ technological capabilities and species vulnerability exacerbate management difficulties. This review provides an overview of diseases prevalent among marine algae, their impact on aquaculture, and the effectiveness of currently adopted treatments. This study highlights the need to improve disease management strategies and highlights the importance of understanding host–pathogen interactions in order to mitigate future epidemics.

L-Lactate dehydrogenase from Cyanidioschyzon merolae shows high catalytic efficiency for pyruvate reduction and is inhibited by ATP

l-Lactate is a commodity chemical used in various fields. Microorganisms have produced l-lactate via lactic fermentation using saccharides derived from crops as carbon sources. Recently, l-lactate production using microalgae, whose carbon source is carbon dioxide, has been spotlighted because the prices of the crops have increased. A red alga Cyanidioschyzon merolae produce l-lactate via lactic fermentation under dark anaerobic conditions. The l-lactate titer of C. merolae is higher than those of other microalgae but lower than those of heterotrophic bacteria. Therefore, an increase in the l-lactate titer is required in C. merolae. l-Lactate dehydrogenase (l-LDH) catalyzes the reduction of pyruvate to l-lactate during lactic fermentation. C. merolae possesses five isozymes of l-LDH. The results of previous transcriptome analysis suggested that l-LDHs are the key enzymes in the lactic fermentation of C. merolae. However, their biochemical characteristics, such as catalytic efficiency and tolerance for metabolites, have not been revealed. We compared the amino acid sequences of C. merolael-LDHs (CmLDHs) and characterized one of the isozymes, CmLDH1. BLAST analysis revealed that the sequence similarities of CmLDH1 and the other isozymes were above 99%. The catalytic efficiency of CmLDH1 under its optimum conditions was higher than those of l-LDHs of other organisms. ATP decreased the affinity and turnover number of CmLDH1 for NADH. These findings contribute to understanding the characteristics of l-LDHs of microalgae and the regulatory mechanisms of lactic fermentation in C. merolae.

Turning the industrially relevant marine alga Nannochloropsis red: one move for multifaceted benefits.

Nannochloropsis oceanica is an industrially relevant marine microalga rich in eicosapentaenoic acid (EPA, a valuable ω-3 polyunsaturated fatty acid), yet the algal production potential remains to be unlocked. Here we engineered N. oceanica to synthesize the high-value carotenoid astaxanthin independent of high-light (HL) induction for achieving multifaceted benefits. By screening β-carotenoid ketolases and hydroxylases of various origins, and strategically manipulating compartmentalization, fusion patterns, and linkers of the enzyme pair, a remarkable 133-fold increase in astaxanthin content was achieved in N. oceanica. Iterative metabolic engineering efforts led to further increases in astaxanthin synthesis up to 7.3 mg g-1, the highest reported for microalgae under nonstress conditions. Astaxanthin was found in the photosystem components and allowed the alga HL resistance and augmented EPA production. Besides, we achieved co-production of astaxanthin and EPA by the engineered alga through a fed-batch cultivation approach. Our findings unveil the untapped potential of N. oceanica as a robust, light-driven chassis for constitutive astaxanthin synthesis and provide feasible strategies for the concurrent production of multiple high-value biochemicals from CO2, thereby paving the way for sustainable biotechnological applications of this alga.

A comparison of the biofouling potential of field-collected and laboratory-cultured Ulva

The marine algae Ulva spp. are commonly used as model biofouling organisms. As biofouling studies are primarily conducted using field-collected specimens, factors including species identity, seasonal availability, and physiological status can hinder the replicability of the results. To address these limitations, a protocol was developed for the on-demand laboratory culture and release of Ulva zoospores. The biofouling potential of laboratory-cultured and field-collected Ulva blades was compared using a waterjet. No significant differences were found between field and laboratory-cultured samples in either spore adhesion (before waterjet) or the proportion of spores retained after waterjet exposure. However, there was significant variability within each session type in pre- and post-waterjet exposures, indicating that spore adhesion and retention levels vary significantly among trial runs. In addition, all our laboratory cultures were Ulva Clade C (LPP complex). In contrast, our field samples contained a mix of Ulva Clade C, U. compressa clade I, and U. flexuosa Clade D. This protocol for on-demand production of Ulva spores can improve biofouling research approaches, enables comparison of results across laboratories and regions, and accelerate the development of anti-biofouling strategies.

Potential of Antioxidant Activity Caulerpa racemosa Extract Using DES Solvent and Different Sonication Times as An Antibacterial Against Pathogenic Bacteria

Caulerpa racemosa, a type of green algae, has been studied for its potential health benefits, including antioxidant and an- tibacterial properties. The extraction of bioactive compounds from marine algae using green solvents like Deep Eutectic Sol- vents (DES) has gained interest due to their efficiency and en- vironmental friendliness. This research aimed to determine the potential antioxidant activity of C. racemosa extract using DES solvents and different sonication times as an antibacterial against pathogenic bacteria. The research employed a Facto- rial Completely Randomized Design (CRD) with two variables: sonication time (10, 20, and 30 minutes) and different DES solvents (ethanol and ethylene glycol (1:20) with 90% aquades, and methanol and glycerol (1:10) with 90% aquades. The highest antioxidant activity was found in DES Methanol-Glycerol (36.39 mg TE/g dw), followed by DES Eth- anol-Ethylene glycol (28.30 mg TE/g dw), both significantly different (p<0.05). The C. racemosa extract inhibited the growth of V. parahaemolyticus with an inhibition zone of 8.08 mm at 50 ppm and 13.13 mm at 1,000 ppm. For V. harveyi, inhibition started at 6.37 mm at 50 ppm, reaching 11.70 mm at 1,000 ppm. DES Methanol-Glycerol with a 10-minute soni- cation provided the highest antioxidant activity and effectively inhibited V. parahaemolyticus and V. harveyi. Extraction of C. racemosa with DES-MG solvent and varying sonication times influences its antioxidant activity and antibacterial properties.