Eucheuma Denticulatum Research Articles

Livelihood aspects of seaweed farming in Rote Island, Indonesia

Indonesia is the main tropical seaweed producer in the world with approximately 70,000 families depending on this activity. The red macroalgae Kappaphycus spp. and Eucheuma denticulatum are the most common species cultivated and used for carrageenan in the processed foods industry. Seaweed farming is an accessible form of mariculture requiring low capital investment and enabling improved living standards in different regions. Nevertheless, farmers suffer from boom and bust cycles due to seaweed price volatility and algal diseases. Limited research has been done on Rote Island, East Nusa Tenggara province, which is among one of the poorest regions in Indonesia where culturing seaweed has become popular. This study assesses seaweed farming practices and their impact on household economy by looking at the overall income generating activities of households involved in seaweed farming. The information was collected using structured interviews with questions related to socio-demographic characteristics, household income, farming practices and challenges. Findings of this study highlight farmers' dependence on seaweed farming activities in southwest Rote, where 50% of the households rely on the income through this activity as their only cash source. During the time of the study, two-thirds of the families were living under the poverty line. Seasonality played a crucial role in seaweed production with negative impacts during the dry season. Thus, families with additional livelihoods seemed to cope better during low production seasons. Seaweed farming practices show room for improvement, and farmers could benefit from activities targeting enhanced productivity of their farms.

The seaweed resources of Malaysia

Abstract The extensive coastline and numerous islands of Malaysia provide various habitats suitable for the growth of a diversity of the marine macroalgae (seaweeds). Since the last checklist of the Malaysian seaweeds was published in 2006, there has been an increase of 17 families, 32 genera, and 75 species. Seven new species were described. The present tally stands at 459 taxa in 72 families; with 35 species in 12 families of Cyanophyta; 113 species in 16 families of Chlorophyta; 95 species in 8 families of Ochrophyta; and 216 species in 36 families of Rhodophyta. Only three species, Kappaphycus alvarezii, Eucheuma denticulatum and Gracilaria manilaensis, are being cultivated commercially. A small seaweed industry centered in Sabah, produces semi-refined carrageenan, which is mainly exported. Some of the biomass is brought over to Peninsular Malaysia, where seaweed products like desserts, health drinks, soaps and air-fresheners, are manufactured and sold. In 2016, Malaysia produced 205,989 tonnes wet weight seaweeds valued at US$24.83 million. The seaweed industry, can be enhanced by increasing the number of farms and farmers, strengthening local seaweed cooperatives and including them in decision-making, as well as by technological advances in the form of new and improved strains, more efficient seed supply and products.

Potassium release kinetics from three invasive algae mixed with different media in leachate column studies

Algae can be an important source of nutrients in agriculture. The objectives of this study were to (1) estimate the potassium (K+) release rate from algae, commercially prepared algal cell walls, and synthetic sources, and (2) better understand effects of polymeric chemistry and potential mechanisms among test materials. Three leachate column studies were conducted for 16 weeks. The experiments consisted of five K+ sources applied at 0, 112, and 336 kg K ha−1. At each leachate collection, half pore volume deionized water was applied and leachate samples were analyzed using a K+ ion selective electrode. Results from these studies showed that the amount of K+ released was significantly higher under synthetic K+ in the first 6 weeks (4100–4200 mg L−1) and sharply declined thereafter. Release of K+ from algal samples was slower in the first 3 weeks and peaked in 8 to 9 weeks (2800–3400 mg L−1). The release of K+ from agar weed Gracilaria salicornia was significantly lower than from carrageenan producer, Eucheuma denticulatum and Kappaphycus alvarezii. Another leachate study was conducted for 6 weeks using agar and carrageenan and found that K+ release from agar columns was significantly lower (10–12%) than from carrageenan. We conclude that the differences in release rate of K+ among dried algae may be explained in part by differences in cell wall composition.

Carotenoid and Chlorophyll Profiles in Five Species of Malaysian Seaweed as Potential Halal Active Pharmaceutical Ingredient (API)

Seaweed, also known as macroalgae, consist of various species that have been gaining the interest of researchers due to the presence of functional bioactive compounds that can be extracted from their biomass. This research aimed to study the chlorophyll and carotenoid content from five species of Malaysian seaweed as potential Active Pharmaceutical Ingredient (API). Three species of red macroalgae, (Eucheuma denticulatum, Gracilaria tikvahiae, and Kappaphycus striatum), green macroalgae (Caulerpa lentillifera ) and one brown macroalga (Padina pavonica) were selected and their chlorophyll and carotenoid contents were determined by using UV-Vis spectrophotometer and HPLC. Their antioxidant and antimicrobial activities were investigated using DPPH Radical Scavenging activity and Disc Diffusion methods, respectively. In terms of carotenoid content, P. pavonica contained the highest amount of carotenoid (100.9 ± 14.7 ug/g DW) and chlorophyll content (7.5 ±1.5 ug/g DW). Meanwhile, based on individual carotenoid content, K. striatum had the highest lutein content (38.6 ug/g DW). Zeaxanthin, beta-carotene, and violaxanthin were significantly higher in C. lentillifera at 21.3 ug/g DW, 10.7 ug/g DW, and 8.9 ug/g DW respectively. Besides that, the antioxidant test showed that P. pavonica presented the strongest DPPH activity with the percentage of inhibition (I %) of (61.0 % ± 0.9). Finally, for the antimicrobial test, strong antimicrobial activities were shown by all the seaweed samples toward E. coli and P. aerugenosa. Overall results of the antifungal test demonstrated moderate antifungal action by all seaweed samples towards M. gypseum and Fusarium sp.

Comparative genomics and systematics of Betaphycus, Eucheuma, and Kappaphycus (Solieriaceae: Rhodophyta) based on mitochondrial genome

Betaphycus Doty, Eucheuma J. Agardh, and Kappaphycus Doty (Solieriaceae, Gigartinales) are the three most commercially important seaweed genera that produce carrageenan. In the present study we provide mitogenomes of Betaphycus gelatinus, Eucheuma denticulatum and Kappaphycus alvarezii. The mitogenomes of these three species contain a set of 50 genes, including 24 protein-coding genes, 2 rRNA genes, and 24 tRNA genes. The mitogenome length ranges from 25,198 bp (Kappaphycus alvarezii) to 25,327 bp (Eucheuma denticulatum). As compared with the previous published mitogenomes of Florideophyceae species, only the species in Gelidiaceae and Pterocladiaceae have smaller mitochondrial genome size than these reported here. At the junction of two transcription units, we identified a stem-loop structure in six representative Gigartinales species, which is presumed to play an important role in the replication and transcription of mitochondrial genes. In Gigartinales the difference in gene order among the four Solieriaceae (B. gelatinus, E. denticulatum, K. alvarezii, K. striatus) and other two Gigartinales species (Chondrus crispus and Mastocarpus papillatus) can be explained by inversion of two tRNA genes. Collinearity analysis of the 12 mitochondrial genomes of Florideophyceae showed considerable sequence synteny across all the species compared, with the exception of a highly variable region between atp6 and rpl20 genes. Phylogenetic analyses based on 21 shared mitochondrial genes showed that the four Solieriaceae species form one clade (Solieriaceae clade). Within this clade, B. gelatinae is basal relative to the other three species. The genus Kappaphycus is more closely related to Eucheuma than Betaphycus.

Composition of Docosahexaenoic Acid, Eicosapentaenoic Acid and Palmitoleic Acid in Eucheuma denticulatum, Sargassum polycystum and Caulerpa lentillifera Ethanolic Extracts by LC-ESI-MS/MS

Composition of Docosahexaenoic Acid, Eicosapentaenoic Acid and Palmitoleic Acid in Eucheuma denticulatum, Sargassum polycystum and Caulerpa lentillifera Ethanolic Extracts by LC-ESI-MS/MS Omega-3 and omega-7 fatty acids have been linked to health benefit in humans. Seaweeds are potential source of fatty acids. Thus, in the current study, a rapid and highly selective method with minimal sample preparation based on liquid chromatographic electrospray ionization tandem mass spectrometry (LC/MS/MS) has been developed and validated for the quantitative determination of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and palmitoleic acid (PA) in Eucheuma denticulatum, Caulerpa lentillifera and Sargassum polycystum ethanolic extracts. The levels of DHA, EPA and PA were in ranges of 6.0-7.0 μg/100 g DW, 51.0- 122.0 μg/100 g DW and 5.0-690.0 μg/100 g DW respectively in the three species of seaweed tested. The standard calibration curves for PA, DHA and EPA were linear (R2 > 0.99) over the concentration ranged between 0-3.00 ng μL-1, respectively, satisfactory recoveries (> 77%), low detection (0.0047- 0.0175 ng μL-1) and quantification limits (0.0156-0.0580 ng μL-1) (LOD and LOQ, respectively). These results indicated that LC-ESI-MS/MS was successfully applied to the analysis of the selected fatty acids in the three groups of seaweeds.

Dilute sulfuric acid hydrolysis of red macroalgae Eucheuma denticulatum with microwave-assisted heating for biochar production and sugar recovery

This study aims to produce biochar and sugars from a macroalga Eucheuma denticulatum using dilute sulfuric acid hydrolysis along with microwave-assisted heating. The reactions were operated at sulfuric acid concentrations of 0.1 and 0.2M, reaction temperatures of 150–170°C and a heating time of 10min. Compared to the raw macroalga, biochar qualities were improved with increased carbon content and lower ash and moisture contents. The calorific value of the biochar could be intensified up to 45%, and 39% of energy yield was recovered. Apart from producing biochar, the highest total reducing sugars were 51.47g/L (74.84% yield) along with a low by-product 5-HMF of 0.20g/L, when the biomass was treated under the optimum conditions at 160°C with 0.1M H2SO4. Thus, this study demonstrated that macroalgae could be potentially used as biomass feedstock under microwave-assisted acid hydrolysis for the production of biofuel and value-added products.

Antifungal activity of crude extracts from brown and red seaweeds by a supercritical carbon dioxide technique against fruit postharvest fungal diseases

Fungal infections are the main cause of decay on fresh fruit during postharvest phase determining severe losses. Postharvest control is performed by fungicides, but their intense use have aroused issue relating to environmental protection and human health prompting to search alternative control means. The use of biofuel-used seaweed extracts by a supercritical carbon dioxide technique could be a valid alternative during postharvest handling of fresh fruit. The aim of this work was to assess the in vitro and in vivo activity of extracts from two brown seaweeds (Laminaria digitata and Undaria pinnatifida) and three red seaweeds (Porphyra umbilicalis, Eucheuma denticulatum and Gelidium pusillum) against three postharvest pathogens (Botrytis cinerea, Monilinia laxa and Penicillium digitatum) using three concentrations of extract (10, 20 and 30gL−1). The total content of fatty acids of the extracts was determined by CG-MS, those of polysaccharides by HIC, and phenolic compounds (phlorotannins) by HPLC-DAD. Twenty fatty acids were quantified in the extracts, while three polysaccharides categories and three phlorotannins classes were identified only in brown seaweed extracts. L. digitata, U. pinnatifida and P. umbilicalis showed the highest antifungal efficacy on in vitro cultures of the pathogens. L. digitata and U. pinnatifida completely inhibited mycelia growing and conidial germination of B. cinerea and M. laxa at the highest dose tested and strongly reduced those of P. digitatum. P. umbilicalis extract strongly inhibited mycelia and conidia growth on all the fungi. E. denticulatum and G. pusillum showed a lower but still significant reduction of mycelia growing and conidia germination on all the pathogens. In trials performed in vivo on wounded fruit, L. digitata, U. pinnatifida and P. umbilicalis extracts strongly suppressed grey mould on strawberries, brown rot on peaches, and green mould on lemons at 30gL−1 dose both in preventive and curative treatments; E. denticulatum and G. pusillum poorly reduced disease development. In all cases, a dose-effect of the treatments was observed with an increase of fruit decay inhibition and reduction of disease severity as the dose of extract applied over the wound increased. Moreover, an increased peroxidase activity in the strawberries/B. cinerea and peaches/M. laxa systems by preventive treatment with 30gL−1 extract was observed. The antifungal activity could be mainly ascribed to a direct toxicity of fatty acids found at the highest concentrations in L. digitata, U. pinnatifida and P. umbilicalis rather than to those of phenolic compounds and phlorotannins; but it could be related to possible peroxidase-mediated systemic resistance mechanisms elicited by the polysaccharides.

Evaluating Three Invasive Algal Species as Local Organic Sources of Potassium for Pak Choi (Brassica rapa, Chinensis Group) Growth

The application of locally available invasive algae biomass as a fertilizer for crop production in Hawaii is being investigated as a substitute for imported chemical fertilizers. Three closely related greenhouse trials were conducted to determine if the algae served as a source of potassium (K) on growth, yield, and K mineral nutrition in pak choi (Brassica rapa, Chinensis group). In the first trial, three algal species (Gracilaria salicornia, Kappaphycus alvarezii, and Eucheuma denticulatum) were applied at five rates of K, each to evaluate their effects on growth and K nutrition of pak choi plants. The pak choi was direct seeded into 0.0027-m3 pots containing peatmoss-based growth media. In trial 2, pak choi was grown in peat media at six rates of K provided by algae (E. denticulatum) or by potassium nitrate (KNO3). In trial 3, the six rates of K were provided through algae (K. alvarezii), KNO3, and potassium chloride (KCl) and were compared for growth and K nutrition. Results from the first greenhouse trial showed no significant differences among the three algal species in yield or tissue K content of pak choi. However, plant yield and tissue K concentration were increased with application rates. The maximum yield and tissue K were observed when K was provided within the range of 250–300 kg·ha−1. Similarly, in Expts. 2 and 3, there were no significant differences between commercial K fertilizers and algal K species for yield. Only K rates were significant for yields and tissue K concentrations. It was concluded that K in the invasive algae was similarly available as K in commercial synthetic fertilizers for pak choi growth in terms of yield and tissue K content under our experimental conditions.

Issue Information

A carageenophyte, Eucheuma denticulatum (Solieriaceae, Rhodophyta) at a mariculture farm in Bali, Indonesia (Photo by R. Terada). Characteristic thermal and irradiance responses on the photosynthesis of Indonesian E. denticulatum and Kappaphycus alvarezii are reported by Borlongan et al. in this issue.Cover picture from: Article link here image

Light and temperature effects on photosynthetic activity of Eucheuma denticulatum and Kappaphycus alvarezii (brown and green color morphotypes) from Sulawesi Utara, Indonesia

SUMMARYKnowledge concerning the effects of several abiotic factors on the physiology of carrageenophytes is essential both in ecological and economic standpoints, to ensure their sufficient supply for the sustainability of seaweed‐based industries. This paper presents the photosynthetic characteristics of farmed carrageenophytes, E ucheuma denticulatum and K appaphycus alvarezii [brown (BRN) and green (GRN) color morphotypes] from Sulawesi Utara (Sulawesi Island), Indonesia, as determined by examining their photosynthetic response across different temperatures and irradiances using dissolved oxygen measurements and pulse‐amplitude modulated fluorometer. Net photosynthesis–irradiance ( P – E ) curves at 26°C revealed that net photosynthetic rates of the three seaweeds gradually increased until the estimated saturation irradiances ( E k ) of 58 μmol photons m− 2 s−1 (49–68 μmol photons m− 2 s−1, 95% Bayesian prediction intervals; BPI) for E . denticulatum, and 158 and 143 μmol photons m− 2 s−1 (134–185 and 99–203 μmol photons m− 2 s−1, 95% BPI) for BRN and GRN K . alvarezii, respectively; and that no photoinhibition was observed at the highest irradiance of 1000 μmol photons m− 2 s−1. All seaweed samples exhibited photosynthetic tolerance to high PAR as shown by their recovery in maximum quantum yields (Fv / Fm ) following chronic exposures; as well as tolerance over a broad range of temperature, which is from 19 to 33°C for E . denticulatum, 20–29°C for BRN K . alvarezii, and 17–32°C for GRN K . alvarezii. Temperature responses of these carrageenophytes indicated that they were well‐adapted to the annual seawater temperatures in the cultivation site; however, they are also likely close to threshold levels for thermal inhibition, given the decline in Fv / Fm above 30°C.

Chemical Composition and Functional Properties of Selected Seaweeds from the Kenya Coast

The aim of the study was to determine the chemical and functional properties of five Kenyan seaweed species namely; (Hypnea musciformis, Eucheuma denticulatum, Laurencia intermedia, Sargassum oligocystum, Ulva fasciata) as a potential fat replacer in chicken sausage processing. The proximate composition was investigated using the standard AOAC methods, while the nitrogen-free extract (NFE) was determined by weight difference of the proximate components. The seaweeds were analyzed for mineral composition using atomic absorption spectrophotometry while the fatty acid profile was determined by gas chromatography. The water holding capacity and the emulsion capacity of the seaweed were determined using AACC procedures. The highest proximate component was NFE (65.06 %) while the least was crude fat (0.87 %). Among the nine minerals analyzed, calcium was the highest (1185.29 mg/100g) while lead was not detected. Saturated fatty acids (SFA) were the highest with a range of 53.03-71.05 % followed by monounsaturated fatty acids (4.83-17.71%) and polyunsaturated fatty acids (PUFA) (2.75 - 10.13%). The highest emulsifying activity was obtained in Ulva fasciata (75.66 %) and Eucheuma denticulatum (75.69 %) while the lowest was obtained in Sargassum oligocystum (59.19 %). The highest water holding capacity was obtained in Sargassum oligocystum (13.75ml/g) while the lowest was recorded in Eucheuma denticulatum (8.42ml/g) and Ulva fasciata (9.16ml/g). The findings of this study demonstrated the potential of seaweeds in improving the chemical and functional characteristics of processed foods.

Efficient utilization of Eucheuma denticulatum hydrolysates using an activated carbon adsorption process for ethanol production in a 5-L fermentor.

A total monosaccharide concentration of 37.8g/L and 85.9% conversion from total fermentable monosaccharides of 44.0g/L from 110g dw/L Eucheuma denticulatum slurry were obtained by thermal acid hydrolysis and enzymatic saccharification. Subsequent adsorption treatment to remove 5-hydroxymethylfurfural (5-HMF) using 5% activated carbon and an adsorption time of 10min were used to prevent a prolonged lag phase, reduced cell growth, and low ethanol production. The equilibrium adsorption capacity (q e) of HMF (58.183mg/g) showed high affinity to activated carbon comparing to those of galactose (2.466mg/g) and glucose (2.474mg/g). The efficiency of cell growth and ethanol production with activated carbon treatment was higher than that without activated carbon treatment. Fermentation using S. stipitis KCTC7228 produced a cell concentration of 3.58gdw/L with Y X/S of 0.107, and an ethanol concentration of 15.8 g/L with Y P/S of 0.48 in 96h.

Thermal and PAR effects on the photosynthesis of Eucheuma denticulatum and Kappaphycus striatus (so-called Sacol strain) cultivated in shallow bottom of Bali, Indonesia

Photosynthetic responses to various temperature and PAR conditions of two carrageenophytes, Eucheuma denticulatum and Kappaphycus striatus (so-called Sacol strain), cultured in shallow areas of Bali, Indonesia, were examined using dissolved oxygen measurements and pulse–amplitude-modulated (PAM) fluorometry. Net photosynthesis–irradiance (P–E) curves at 26 °C revealed that the values of Pmax for E. denticulatum and K. striatus were 13.76 and 5.02 μg O2 gfw−1 min−1 (12.38–15.12 and 4.55–5.50 μg O2 gfw−1 min−1, 95 % Bayesian prediction interval (BPI)), respectively. Photoinhibition was not observed even at 1000 μmol photons m−2 s−1. Gross photosynthesis and respiration characteristics over a range of temperatures (8–36 °C) revealed optimum temperature for photosynthesis to be 31.1 °C for E. denticulatum, and 31.6 °C for K. striatus. These characteristics of photosynthesis indicate that both farmed seaweeds are well adapted to the light and temperature conditions of the cultivation site. However, studies on longer timescales for photochemical efficiency, photosynthesis, and respiration are still needed to determine their limits of tolerance. We also hypothesize that higher values of photosynthetic parameters for E. denticulatum suggest that this species is relatively superior in productivity under optimal conditions, conditional on the farming method.

A Correlation of Rapid Cardy Meter Sap Test and ICP Spectrometry of Dry Tissue for Measuring Potassium (K+) Concentrations in Pak Choi (Brassica Rapa Chinensis Group)

ABSTRACTNutritional status of vegetable crops is often monitored by analysis of dried plant tissues, which is costly and often time consuming. Two greenhouse trials were conducted, at the University of Hawaii at Manoa, Magoon facilities, to evaluate the portable cardy ion meter (CIM) in determining potassium (K+) status in fresh petiole sap of pak choi as compared with standard laboratory methods. In the first greenhouse trial, three algae species (Gracilaria salicornia, Kappaphycus alvarezii, and Eucheuma denticulatum) were used to apply five rates of K+ (0, 84, 168,252, and 336 kg.ha−1). The pak choi was directly seeded into 4 L pots and was grown in peat moss. In the second greenhouse trial, K+ was provided through Eucheuma denticulatum and potassium nitrate (KNO3) at five rates (0,112, 168, 224, 280, and 336 kg.ha−1) in peat moss and soil media. At harvest, K+ concentrations in fresh petiole sap were analyzed immediately with CIM and the dried samples were analyzed by inductively coupled plasma spectroscopy (ICP) measurement. The results showed increase in leaf K+ content at higher rates and the maximum concentration of leaf K+ at 4500–5300 mg/L for sap and 8–9% for tissue was obtained when K+ was provided between 224 and 284 kg.ha−1. There was a close correlation between the CIM readings and the ICP method (r = 0.8048 and 0.8314) from the first and second GH results, respectively. The results suggest that the CIM could be used for the rapid monitoring of the relative K+ status of plants. The data further suggested 4500–5000 mg K/L for fresh petiole sap and 7.5% K+ in tissue as critical levels for K+ concentration in pak choi.

Cloning and characterizing cDNA sequences coding high-mannose n-glycan binding lectins from cultivated red algae Eucheuma denticulatum and Kappaphycus striatum

The red algae, Eucheuma denticulatum and Kappaphycus striatum have been widely cultivated in Vietnam as a source of carrageenophytes for industry. In the past, biochemical properties of lectins isolated from these algae has been characterized and evaluated extensively. However, gene coding for such lectins isn’t studied yet. In this study, their full length cDNA is amfplified using cDNA ends (RACE) methods. Sequence analysis revealed that cDNA of EDA-2 from E. denticulatum consisted of 1,158 bp containing 103 bp of a 5'untranslated region, 248 bp of 3'untranslated region, and 807 bp of an open reading frame; and cDNA of KSA-2 from K. striatum consisted of 1174 bp containing 94 bp of the 5'-untranslated region, 273 bp of 3'untranslated region and 807 bp of the open reading frame. The cDNA of both EDA-2 and KSA-2 encoded for a polypeptide of 269 amino acids including an initiating methionine, but differed in sequences and molecular masses. The deduced amino acid sequences of EDA-2 and KSA-2 composed of four tandem repeated domains with about 67 amino acids each. The primary structure of EDA-2 and KSA-2 is highly similar to those of the high mannose N-glycan specific lectins including OAA from cyanobacterium, BOA, MBHA and PFA from bacteria, and ESA-2, KAA-1, KAA-2 from macro red algae, which showed strong anti-HIV and anti-influenza virus activities. These results indicate that these cultivated algae are becoming promising materials for production of anti-virus reagent or functional food that can prevent virus infection in future.

Heavy metal biosorption potential of a Malaysian Rhodophyte (Eucheuma denticulatum) from aqueous solutions

Biosorption is a promising technology for the removal of heavy metals from industrial wastes and effluents. In the present study, biosorption of Pb2+, Cu2+, Fe2+ and Zn2+ onto the dried biomass of Eucheuma denticulatum (Rhodophyte) was investigated as a function of solution pH, contact time, temperature and initial metal ion concentration. The experimental data were evaluated by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The sorption isotherm data followed Langmuir and Freundlich models, and the maximum Langmuir monolayer biosorption capacity was found as 81.97, 66.23, 51.02 and 43.48 mg g−1 for Pb2+, Cu2+, Fe2+ and Zn2+, respectively. The sorption kinetic data followed pseudo-second-order and intraparticle diffusion models. Thermodynamic study revealed feasible, spontaneous and endothermic nature of the sorption process. Fourier transform infrared analysis showed the presence of amine, aliphatic, carboxylate, carboxyl, sulfonate and ether groups in the cell wall matrix involved in metal biosorption process. A total of nine error functions were applied in order to evaluate the best-fitting models. We strongly suggest the analysis of error functions for evaluating the fitness of the isotherm and kinetic models. The present work shows that E. denticulatum can be a promising low-cost biosorbent for removal of the experimental heavy metals from aqueous solutions. Further study is warranted to evaluate its potential for the removal of heavy metals from the real environment.

Growth performance of the sea cucumber Holothuria scabra and the seaweed Eucheuma denticulatum: integrated mariculture and effects on sediment organic characteristics

Deposit-feeding sea cucumbers play a key role in marine ecosystems through biotur- bation, burrowing and feeding on organic matter in marine sediments. Many deposit-feeding holothurians have therefore been recommended for integrated multitrophic aquaculture systems (IMTA). We set up an integrated mariculture system of sea cucumber Holothuria scabra and sea- weed Eucheuma denticulatum in Bweleo, Unguja Island of Zanzibar, Tanzania, to investigate the effect of stocking density on the growth and survival of culture species, total organic matter (TOM) and total organic carbon (TOC) content in the sediment. Treatments that included a fixed stocking density (500 g, ca. 200 g m �2 ) of E. denticulatum and 4 sea cucumber stocking densities (monoculture, low, medium and high density; 0, 150 ± 5, 236 ± 24, 345 ± 48 g m �2 , mean ± SD) of medium-sized H. scabra (114 ± 37 g) were established. Stocking density of H. scabra did not influ- ence survival of either species. Seaweed cultured under high stocking density of H. scabra had a higher specific growth rate of 2.33% d �1 than that cultured at the medium or low densities or with- out sea cucumbers. Sea cucumbers cultured at low stocking density had a higher mean growth rate of 0.80 g d �1 compared to those cultured at medium or high densities. TOM and TOC in sed- iments decreased over the experimental period at medium sea cucumber stocking density, while at low and high stocking densities, organic matter accumulated. The study demonstrates that the integration of E. denticulatum and H. scabra at 200 g m �2 enhances seaweed growth and can reduce organic matter content in the sediments.

Evaluation of ethanol production and bioadsorption of heavy metals by various red seaweeds.

The objective of this study was to evaluate ethanol production and bioadsorption with four red seaweeds, Gelidium amansii, Gracilaria verrucosa, Kappaphycus alvarezii and Eucheuma denticulatum. To produce ethanol, thermal acid hydrolysis, enzymatic saccharification and fermentation was carried out. After pretreatment, 38.5, 39.9, 31.0 and 27.5g/L of monosaccharides were obtained from G. amansii, G. verrucosa, K. alvarezii and E. denticulatum, respectively. Ethanol fermentation was performed with Saccharomyces cerevisiae KCCM 1129 adapted to 80g/L galactose. The ethanol productions by G. amansii, G. verrucosa, K. alvarezii and E. denticulatum were 18.8g/L with Y EtOH=0.49, 19.1g/L with Y EtOH=0.48, 14.5g/L with Y EtOH=0.47 and 13.0g/L with Y EtOH=0.47, respectively. The waste seaweed slurries after the ethanol fermentation were reused to adsorb Cd(II), Pb(II) and Cu(II). Using langmuir isotherm model, Cu(II) had the highest affinity for waste seaweeds with the highest q max and electronegativity values among three heavy metals.

Identification and characterization of microRNAs in Eucheuma denticulatum by high-throughput sequencing and bioinformatics analysis

ABSTRACTEucheuma denticulatum, an economically and industrially important red alga, is a valuable marine resource. Although microRNAs (miRNAs) play an essential role in gene post-transcriptional regulation, no research has been conducted to identify and characterize miRNAs in E. denticulatum. In this study, we identified 134 miRNAs (133 conserved miRNAs and one novel miRNA) from 2,997,135 small-RNA reads by high-throughput sequencing combined with bioinformatics analysis. BLAST searching against miRBase uncovered 126 potential miRNA families. A conservation and diversity analysis of predicted miRNA families in different plant species was performed by comparative alignment and homology searching. A total of 4 and 13 randomly selected miRNAs were respectively validated by northern blotting and stem-loop reverse transcription PCR, thereby demonstrating the reliability of the miRNA sequencing data. Altogether, 871 potential target genes were predicted using psRobot and TargetFinder. Target genes classification and enrichment were conducted based on Gene Ontology analysis. The functions of target gene products and associated metabolic pathways were predicted by Kyoto Encyclopedia of Genes and Genomes pathway analysis. A Cytoscape network was constructed to explore the interrelationships of miRNAs, miRNA-target genes and target genes. A large number of miRNAs with diverse target genes will play important roles for further understanding some essential biological processes in E. denticulatum. The uncovered information can serve as an important reference for the protection and utilization of this unique red alga in the future.