Seasonal biochemical fingerprints of Kappaphycus alvarezii grown in Southern Brazil: Efficient extraction of pigments and mycosporine-like amino acids using biosolvents

Bio-based nanocomposite films from Kappaphycus alvarezii for packaging applications

The current study aimed to ascertain the growth, antioxidant capacity, intestinal architecture, digestive enzyme activity, and disease resistance of S. agalactiae of Nile tilapia (Oreochromis niloticus) fed a diet enriched with carrageenan. Using an alkali method, the carrageenan was extracted from the seaweed Kappaphycus alvarezii. Its antiviral and antibacterial properties against Tilapia Lake virus and aquatic pathogens like Aeromonas veronii, Edwardsiella tarda, Streptococcus agalactiae, and Streptococcus iniae were assessed. A total of 450 healthy juvenile Nile tilapia (4.43 ± 0.71g) were randomly divided into five experimental groups, 30 fish per group, with three replicates. The water quality parameters such as dissolved oxygen (5.65 ± 0.2mg/L), pH (7.75 ± 0.51), temperature (27.75 ± 1.5°C), and ammonia (0.2 ± 0.08mg/L) were monitored. Group 1 (control, normal feed), group 2 (10g/kg), group 3 (20g/kg), group 4 (40g/kg), and group 5 (80g/kg) all had varying carrageenan concentrations throughout the 60-day study. Then, 30 fish from each group were intraperitoneally challenged with S. agalactiae, and mortality was recorded for the next 15days. The results showed substantial improvements in initial weight, weight gain rate, survival rate, condition factor, and specific growth rate in the G4 groups compared to the G1 group. The carrageenan-based dietary supplements at the concentration of 20g/kg enhance digestive enzyme activity (amylase, protease, and lipase) in fish, improving nutrient absorption and overall growth performance. The antioxidant activities, such as a significant increase in SOD, CAT, and GSH capacity and a remarkable decrease in MDA content, were observed in the liver of fish fed carrageenan diets. IgM antibody values, measured by ELISA, peaked G3-treated fishes when compared to other groups. The gene expression analysis using qRT-PCR showed the significant increase immune genes like IL-1β, IL-8, and IgM in the G3-treated fishes when compared to the others. The challenge test with S. agalactiae resulted in lower mortalities by carrageenan administration in a dose-dependent manner, and the highest mortality was observed in fish fed the G1 diet. The study concludes that the inclusion of carrageenan at the rate of G3 is recommended to improve growth performance, antioxidant capacity, and immunity, as well as to regulate intestinal morphology and promote resistance against S. agalactiae in Nile tilapia.

Responses of antioxidant defense enzymes and thiols in root nodules of black gram following foliar application of Kappaphycus alvarezii seaweed based biostimulant

Seasonal biochemical characterization of the red seaweed Kappaphycus alvarezii cultivated in southern Brazil

Red algae (Kappaphycus alvarezii) are a marine resource containing bioactive compounds, such as flavonoids and carotenoids, with potential antioxidant properties. This study aimed to develop lozenge formulations of red algae powder using direct compression, optimize the excipient composition, and evaluate the physicochemical properties and antioxidant activity. Red algae powder was characterized microscopically and by LC–MS, confirming the presence of quercetin, rutin, kaempferol, and astaxanthin in the powder. Five lozenge formulations (F1–F5) were prepared using varying concentrations of hydroxypropyl methylcellulose (HPMC) and starch. In-process evaluation included flow rate, angle of repose, loss on drying, and particle size distribution, while post-compression testing covered organoleptic properties, weight variation, hardness, friability, surface abrasion, and disintegration time. Antioxidant activity was determined using the DPPH radical scavenging assay, with quercetin as the standard. All formulations met the pharmacopeia standards, with hardness ranging from 74.3–111.1 N, friability 0.61–0.98%, and disintegration times 6.61–15.88 min. Optimization using a Simplex Lattice Design identified Formula 3 (3.5% HPMC and 10.5% starch) as the most desirable composition. The red algae powder and lozenge exhibited weak antioxidant activity, with IC₅₀ values of 5,969 ppm and 6,854 ppm, respectively. These findings demonstrate that lozenges containing red algae powder can be successfully produced with acceptable physical properties; however, improvement of raw material standardization or enrichment is required to enhance antioxidant efficacy.

The study on the application rates and frequencies of Kappaphycus alvarezii drippings (KD) on rice blast (Pyricularia grisea) management of potted rice under reduced fertilization was conducted from January to June 2022 at San Isidro, Magsaysay, Davao del Sur using double D rice variety. The study aimed to assess the days to leaf and panicle blast symptom apprearance, assess the severity of leaf blast, incidence of panicle blast, and other disease, and evaluate the agronomic, yield, and yield parameters of potted rice. The application rates (ml/L) of KD (Factor A) influences the number of days to leaf and blast appearance and severity of leaf blast but not on panicle blast appearance and incidence. The application of 20 ml/L delayed the symptom appearance which results to low percent severity of leaf blast. Moreover, significant differences on the percent severity of bacterial blight were recorded among the application rates (Factor A), frequencies (Factor B) of KD and levels of inorganic fertilizer (Factor C) and the interaction of the three factors. On agronomic parameters, high significant differences on plant height (cm), panicle length (cm) and number of productive tillers per plant were recorded with the application of 20 ml/L of KD weekly, bi-weekly and monthly across levels of inorganic fertilizer. Significant interaction effects of the application rates (Factor A) and frequencies (Factor B) of KD were observed on the weight of 1000 grains but not on yield (kg/ha).

Abstract Kappaphycus alvarezii , the biomass of red seaweed in many coastal regions, can be investigated for its potential as an additive ingredient in the manufacturing of solid soap, in line with the principles of the blue economy post-harvest development program. The research aims to characterize solid soap-making by evaluating its physicochemical properties. The methodology involved cold-processed soap making, extracting K. alvarezii with hot water and incorporating it into a solid soap formulation. The resulting solid soap had a pH of 10.00±0.14; moisture content of 12.44±0.71 %; free fatty acid of 0.88±0.23 %; free alkali as NaOH of 0.084±0.003 %; and mold count of <10 CFU/g. The implications of this research indicate that K. alvarezii can be additive in solid soap production, with the potential to enhance its properties and align with sustainable practices of the blue economy. This methodology could yield economic prospects for coastal communities and encourage the application of marine resources in the development of value-added products.

Carrageenan is a high-in-market demand product extracted from Kappaphycus alvarezii, but it generates substantial solid waste as a by-product, at around 65-70%.Carrageenan solid waste (CSW) contains high cellulose, which is lighter in weight, but stronger in bond characteristics.This makes CSW suitable as a substitute material for sand to develop cellular lightweight concrete (CLC).Meanwhile, fly ash (FA), a charcoal by-product, can be utilised as a substitute cement material due to its high silica and alumina content.Combining CSW and FA can result in a sustainable alternative material.The objective of this study was to develop and characterize CLC using a combination of CSW and FA.The finding shows that the combination significantly affected (p<0.05) the physico-mechanical properties of the compressive strength, split tensile, and water absorption, but there is no significant difference (p> 0.05) in the specific gravity.The findings also shows that the best combination of CSW and FA is the one with a ratio of 100% and 20% (T8), which results in the following characteristics: 0.783 kg/cm 3 of the specific gravity, 1.231 0.07 MPa of the compressive strength score, 0.171 0.03 MPa of the split tensile score, and 47.67 0.58 % of water-absorption percentage value.Furthermore, the study suggested that higher ratio of cement should be increased to higher the physico-mechanical properties of CLC.Future research should be conducted, concerning durability, thermal conductivity, or weathering resistance and practical application as non-structural CLC.

Kappaphycus alvarezii is a commercially valuable red seaweed cultivated for biomass and phycocolloid production. Enhancing its productivity, stress tolerance, and phycocolloid yield requires genetic diversification and optimized cultivation techniques. This study investigated the effects of different light intensities on growth, pigment composition, and gene expression in wild K. alvarezii to inform hatchery cultivation strategies. Eight wild-type strains were clonally cultivated under low, medium (control), and high light conditions for 28 days. High light resulted in the highest daily growth rate (6.03% ± 1.86%), whereas phycoerythrin (PE) levels were significantly higher under low light conditions. Gene expression analysis revealed that high light upregulated antioxidant-related genes (e.g., carotenoid-associated genes) and genes involved in DNA synthesis and repair, while repressing photosynthesis-related genes, likely as a protective response against oxidative stress. Low light reduced the expression of light-harvesting-related genes and intensified the expression of polysaccharide-degradation genes, potentially compromising carrageenan biosynthesis. Notably, the lectin KAA protein was highly induced under low light, suggesting a potential protective role against mannose-dependent pathogens. These results highlight the acclimative mechanisms of K. alvarezii under light stress and provide insights into metabolic regulation and energy allocation. Understanding these responses can help inform seaweed farmers about optimal cultivation depth and light exposure to maximize growth and enhance carrageenan yield, thereby contributing to sustainable aquaculture practices. Furthermore, transcriptome profiling identified key genes associated with carrageenan biosynthesis; together with the identification of light-regulated processes, these results provide candidate molecular targets for future genotype-based improvement and cultivation strategies aimed at enhancing carrageenan production.

Abstract This study investigates the effects of varying potassium hydroxide (KOH) concentrations and immersion durations on the physicochemical properties of carrageenan extracted from sap-free Kappaphycus alvarezii chips. Research has been conducted to measure seven parameters: gel strength, viscosity, elasticity, moisture content, ash content, acid-insoluble ash, and KOH requirement, to improve the quality of sap-free K. alvarezii chips using low-concentration alkali. The treatment conditions for the research are A1–A4 for KOH concentration; B1–B3 for immersion time. Sap was extracted from fresh K. alvarezii thallus using a rotary screw press. The thallus was then immersed in 0.0, 0.5, 1.0, and 1.5% KOH solutions for 0, 5, and 15 minutes of immersion time. Results indicate that higher KOH concentrations and longer immersion times, as well as the combination of 1.5% KOH using a 15-minute immersion time, significantly enhance gel strength (218.73 g/cm 2 ), viscosity (77.50 cP), and elasticity (39.49 N/m 2 ), while reducing moisture and acid-insoluble ash content. Ash content remained stable across treatments, and KOH requirement increased with both concentration and duration. These findings suggest that optimized alkali treatment improves carrageenan quality and processing efficiency, offering a scalable pathway for sustainable biopolymer production.

ABSTRACT Although growing in popularity in developed countries, organic kiwifruit (Actinidia deliciosa) production still has several operational challenges, including limited availability of organically approved growth regulators, nutrient inputs and insecticides. In this study, 11 biostimulant treatments were tested, including T1: Water spray (control), T2: 5% KA sap (Kappaphycus alvarezii), T3: 10% KA sap, T4: 5% GE sap (Gracilaria edulis), T5: 10% GE sap, T6: 5% AN sap (Ascophyllum nodosum), T7: 10% AN sap, T8: 5% Vermiwash, T9: 10% Vermiwash, T10: 5% Humic acid and T11: 10% Humic acid. The biostimulants were used as root zone soil applications four times per year: 1) before flower bud opening, 2) at 1 month after fruit set, 3) at 3 months after fruit set, and finally 4) at 5 months after fruit set. In terms of growth attributes of the kiwifruit cultivars Allison and Hayward, treatment T2: 5% KA sap showed the best results for sprouting percentage and yield per vine, while treatment T8: 5% Vermiwash exhibited the best results for fruitful bud percentage, fruit shoot−1 and grade-A fruit percentage. The majority of the quality traits were found to be significantly higher with the application of treatment T2: 5% KA sap, compared with the control. DPPH and ABTS assays showed maximum values with T8: 5% Vermiwash and T10: 5% Humic acid, respectively. It was concluded that the application of biostimulants like seaweed extracts, vermiwash and humic acids can be used to increase the quality, yield and production economics of organic kiwifruit production.

Seaweed extract and humic acid granules are increasingly recognized as effective biostimulants that help with sustainable soil management and improve crop productivity. Seaweed extract often made from brown macroalgae like Ascophyllum nodosum, Sargassum species and Kappaphycus alvarezii provides bioactive compounds, including phytohormones, polysaccharides, amino acids, and micronutrients. These compounds promote root development, boost stress tolerance, and stimulate important metabolic processes. Humic acid granules improve soil fertility by enhancing soil structure, increasing cation exchange capacity, retaining nutrients better, and supporting beneficial microbial activity. Together, these amendments create synergistic effects that enhance soil properties, such as organic carbon content, moisture retention, and aggregate stability. Their combined use has been proven to increase nutrient uptake, boost chlorophyll synthesis, improve photosynthesis, and strengthen plants’ resistance to abiotic stresses. These advantages lead to higher crop yields by about 15 to 30%, better produce quality, and more efficient use of inputs in field and horticultural crops. The environmental benefits include reducing reliance on synthetic fertilizers, lowering greenhouse gas emissions, and promoting long-term soil health. Economically, using seaweed and humic acid granules offers better benefit-to-cost ratios and encourages the adoption of regenerative and climate-smart farming practices. This review summarizes current scientific evidence on the mechanisms, interactions, and agronomic benefits of these natural amendments, showcasing their importance in sustainable agriculture.

ABSTRACT Climate variability increases the pressure on the sustainability of seaweed cultivation in tropical regions. This study aimed to analyse the dynamics of relocation and expansion of Kappaphycus alvarezii cultivation in Bone Bay, Indonesia, by integrating high-resolution multitemporal PlanetScope imagery with sea surface temperature (SST) and rainfall data obtained from MODIS and CHIRPS during the period 2022–2024. An Object-Based Image Analysis (OBIA) approach combined with the Random Forest algorithm was applied to map the spatial distribution of cultivation areas and quantify temporal changes in the area and number of cultivation units. Classification results showed consistent performance with a moderate level of accuracy, with overall accuracy values ranging from 68.4% to 72.5% and Kappa coefficients between 0.58 and 0.67, indicating that high-resolution optical imagery is capable and temporally stable in detecting seaweed cultivation areas in complex coastal environments. Temporal analysis revealed clear seasonal and interannual variability, with a tendency for cultivation area expansion during the monsoon transition period (March–September) and contraction during the rainy season (October–December). Statistical analysis showed a consistent negative relationship between increasing sea surface temperature and the area and number of cultivation units, whereas rainfall only had a positive effect at moderate intensity levels. This study confirms the novelty of an integrative approach between high-resolution satellite imagery and climate variables as a basis for developing a seaweed cultivation management system that is adaptive to future climate variability and changes.

ABSTRACT Seaweed farming is a vital economic activity for coastal communities in the Western Indian Ocean, with growing potential in food, bio‐stimulants, pharmaceuticals and environmental management. Some farmed species, such as Eucheuma denticulatum and Kappaphycus alvarezii , are known to be sensitive to extreme weather events such as El Niño rains, with direct implications for production and livelihoods. This study assessed the impacts of the November–December 2023 El Niño event on seaweed farms in three villages (Kibuyuni, Tumbe and Bati‐Mwazaro) along the south coast of Kenya. The assessment focused on changes in production, labour requirements and farm management practices. Data were collected through face‐to‐face interviews with 99 seaweed farmers and analysed using quantitative and qualitative approaches. Production was found to have increased steadily from September to November 2023 but declined sharply in December 2023 and January 2024, during and immediately after the El Niño. Farmers in Kibuyuni demonstrated faster recovery and maintained more active ropes in the water, resulting in higher post‐El Niño harvests, whereas Bati‐Mwazaro and Tumbe reported lower yields. Additionally, farm labour shortages were a major constraint across all villages (reported by 98% of respondents in Kibuyuni, 94% in Bati‐Mwazaro and 87% in Tumbe). Kibuyuni farmers had a greater proportion of ropes deployed at sea, whereas Bati‐Mwazaro and Tumbe farmers retained most of their ropes at home, indicating reduced active farm area and slower recovery. These findings show how a single extreme rainfall event can disrupt seaweed value chains, delay recovery over multiple cropping cycles and exacerbate vulnerability in already marginalized coastal villages. The study highlights priority adaptation and management options, including integrated early warning and farming calendars, spatial planning to reduce exposure to flood plumes, strengthened farmer organizations and input supply systems and development of policy instruments for insurance and emergency support to buffer future El Niño shocks.

Seaweed farming, a crucial part of the blue economy in Sorsogon, Philippines, operates in a dynamic and frequently unpredictable environment. This environment is vulnerable to various factors that can affect its economic viability and long-term sustainability. These challenges include fluctuating market prices, environmental risks like climate change and disease outbreaks (such as the “ice-ice” disease), and operational inefficiencies. For small-scale farmers, these risks can be particularly devastating, threatening their livelihoods and hindering the sector’s growth. This study analyzed seaweed farming operations and risks using Risk Management Theory. Data from a survey of 115 farmers in Sorsogon City and Castilla, along with interviews with stakeholders, and experts, revealed a sector dominated by small-scale and medium-scale ventures, primarily cultivating Kappaphycus alvarezii through fixed-bottom long lines. While all farmers accessed government propagules, only 20% received direct financial support, highlighting a liquidity gap. Environmental hazards, particularly typhoons and “ice-ice” disease, drove yield volatility. To mitigate these risks, the study recommends Risk Avoidance through the mandatory conversion of unviable farming systems, and Risk Reduction via the distribution of climate-resilient genotypes. These findings provide a strategic roadmap for policy interventions aimed at transforming Sorsogon’s seaweed industry from a subsistence activity into a resilient commercial enterprise.

Kharif rice (Oryza sativa L.) production systems in India frequently encounter challenges, including erratic monsoon patterns, declining soil fertility and imbalanced nutrient management. This field experiment was carried out to evaluate the synergistic influence of foliar-applied seaweed-based bio-stimulant (Kappaphycus alvarezii sap) and graded nitrogen doses on the growth and productivity of kharif rice (cv. RNR-15048). The experiment was arranged in a split-plot design with three nitrogen doses (0, 60 and 120 kg ha) in main plots and four bio-stimulant doses (0, 5, 10 and 15 mL L-1) as sub-plots which were replicated thrice. The results revealed significant improvements in growth attributes at different growth stages of rice. Yield components such as panicle bearing tillers m-2, panicle length (cm), filled grains panicle-1 and 1000-grain weight (g) were also significantly influenced due to the application of bio-stimulants and varied nitrogen levels. In case of bio-stimulants, the treatment with 15 mL L-1 K. alvarezii sap produced the highest grain and stover yield (3.8 t ha-1 and 4.8 t ha-1, respectively) and with regards to nitrogen levels, application of 120 kg ha-1 of N recorded the maximum grain yield (4.1 t ha-1) and stover yield (5.1 t ha-1) of rice. The findings demonstrate that integrating bio-stimulant application at of 15 mL L-1 with an appropriate nitrogen level of 120 kg ha-1 can improve the growth and productivity of kharif rice.

A sheet face mask is a type of facial skincare cosmetic applied to the entire face to provide hydration, a refreshing sensation and skin tightening. A paradigm shift is now underway, fuelled by consumer concerns over the long-term safety of synthetic chemicals used in these products and the broader ecological footprint of cosmetic production. Consequently, κ-carrageenan is an alternative to these synthetic chemicals due to its natural origin, being free of harmful chemicals, gelling and hydration properties. The red seaweed, Kappaphycus alvarezii, the only seaweed species commercially cultivated in Sri Lanka is a rich source of κ-carrageenan, however, it has not yet been used locally to extract carrageenan and test its application in skincare cosmetics. Precipitation of κ-carrageenan using KCl is a critical step in carrageenan extraction process as it imparts strength to carrageenan gels. In this study, carrageenan was extracted using three concentrations of KCl and its suitability for a sheet face mask gel was tested across three carrageenan concentrations. The results showed that comparatively higher yields of 31.89±0.05 and 33.52±2.50 were obtained at 2.50% and 3.50% KCl concentrations, respectively. All tested characteristics for a leave-on sheet face mask gel were achieved at 1.00% carrageenan concentration prepared using carrageenan extracted at 3.50% KCl concentration. Notably, prepared carrageenan gels were able to moisturise the skin without altering skin oiliness.

Comprehensive insights into red seaweed (Kappaphycus alvarezii) and its bioactive carrageenan and phenolic components in addressing metabolic syndrome

Marine algae represent an abundant and renewable biological resource with growing relevance in the fields of health and biomedicine due to their capacity to produce structurally diverse bioactive compounds. Both microalgae and macroalgae, including representatives of the red (Rhodophyta), green (Chlorophyta), and brown (Phaeophyta) algal groups, generate metabolites that support their ecological survival while also exhibiting notable pharmacological properties. This review consolidates current research findings across four major categories of biological activity: anti-inflammatory, antioxidant, anti-obesity, and anticoagulant effects. Polysaccharides such as fucoidans isolated from brown algae (e.g., Undaria pinnatifida and Macrocystis pyrifera), along with extracts derived from red algae (Kappaphycus alvarezii) and green algae (Ulva pertusa), have demonstrated significant immunomodulatory and enzyme-inhibitory activities. In addition, marine algae are important sources of antioxidant molecules, including polyphenols, carotenoids, and sulfated polysaccharides, identified in species such as Callophyllis japonica, Gracilaria tenuistipitata, Ulva lactuca, and Ulva reticulata. Certain algal metabolites—such as fucoxanthin, siphonoxanthin, and phlorotannin—exert anti-obesity effects through multiple metabolic pathways, while sulfated galactans and fucans provide promising alternatives to conventional anticoagulants. Beyond their bioactive potential, marine algae also offer a comprehensive nutritional profile, reinforcing their value as functional foods and as sources of biomedical compounds.