Gracilaria Dura Research Articles

Feasibility of farming the agarose-yielding red alga Gracilaria dura using tube-net cultivation in the open sea along the Gujarat coast of NW India

ABSTRACT Despite some perceptions of economic risk, the global aquaculture industry continues to attract new entrepreneurs and investors. However, to sustain this trend, innovative and cost-effective strategies are needed. In recent years, algal farming has been shown to be a sustainable activity in the global Blue Economy. In 2015, harvests of the red algal agarophyte genus Gracilaria surged to over 114,100 tons dry weight which constituted ca. 91% of the total raw material for industrial agar production. We carried out a trial of experimental farming of the agar-yielding alga known as Gracilaria dura using a tube-net method along the Gujarat coast, India. The mean daily growth rate (DGR) of this agarophyte ranged from 1.88 ± 0.23% day−1 to 3.30 ± 0.25% day−1. Similarly, the mean yield varied between 0.62 ± 0.03 kg and 1.05 ± 0.02 kg fresh wt m−1 of tube-net. A Pearson correlation showed that both DGR and biomass yield were positively correlated with temperature. In addition, the DGR was significantly positively correlated with air temperature (r = 0.916; p < 0.01) whereas biomass yield was also positively correlated with surface seawater temperature (r = 0.986; p < 0.001). The economic projections for four harvests per year revealed that the value of the product was US$5577, while the investment required for the necessary tube-net infrastructure was US$1797 thereby providing US$1890 as profit to single farmers, a significant amount in the coastal communities of Gujarat. Thus, undertaking commercial farming of G. dura in Indian waters could diversify the livelihood of artisanal, coastal fishermen and further encourage the indigenous production of agarose.

Gracilaria dura extract confers drought tolerance in wheat by modulating abscisic acid homeostasis

Water stress severely reduces the production of wheat. Application of seaweed extracts have started to show promise in protecting plants from environmental stresses as they contain several biostimulants. However, the modes of action of these biostimulants are not clear. Here, we investigated the role of Gracilaria dura (GD), a red alga, in conferring stress tolerance to wheat during drought under glasshouse and agro-ecological conditions by integrating molecular studies with physiological and field investigations. GD-sap application conferred drought tolerance (as the biomass increased by up to 57% and crop yield by 70%), via facilitating physiological changes associated to maintaining higher water content. GD-sap application significantly increased ABA accumulation (2.34 and 1.46 fold at 4 and 6 days of drought, respectively) due to enhanced expression of biosynthesis genes. This followed an activation of ABA response genes and physiological processes including reduced stomatal opening, thus reducing water loss. Moreover, GD-sap application enhanced the expression of stress-protective genes specifically under water stress. Treatment with fluridone, an ABA inhibitor, further support the role of ABA in GD-sap mediated drought tolerance in wheat. The findings of this study provide insights into the functional role of GD-sap in improving drought tolerance and show the potential to commercialize GD-sap as a potent biostimulant for sustainable agriculture in regions prone to drought.

English

English

Farming of agarophytes in India—a long-time sustainability for the industry and preserving wild stocks

In India, food-grade agar is produced from Gracilaria edulis while bacteriological-grade agar is extracted from Gelidiella acerosa. Agarose is directly obtained from Gracilaria dura. Seaweeds for agar production mainly come from wild stocks located in reefs of the Gulf of Mannar, southeast coast. Landings of Gr. edulis were peak (982 dry t) during 1990 while landings of Ge. acerosa reached maximum (665 dry t) during 2002–2003. Overexploitation is leading to a decrease in biomass of these two algae at an alarming rate for the last decade. Commercial cultivation of agarophytes is yet to increase in India in spite of growing pressure on wild stocks triggered by increase in demand of raw material by the industry. Taking this into consideration, a number of efforts have been initiated to develop feasible cultivation methods for agarophytes. The present paper summarizes various methods developed for commercial cultivation of Gr. edulis, Gr. dura, Gracilaria verrucosa and Ge. acerosa in the open sea. We also discuss the challenges in the development of commercial farming of agarophytes in India.

Gene Over-Expression of Glycerol-3-phosphate Dehydrogenase in Some Marine Algae of Egypt.

Studies focusing a survey or a comparison between freshwater and marine algae are relatively Algae exhibit a wide range of acclimation in response to induced salinity. However, studies focusing a survey or a comparison between freshwater and marine algae are relatively scarce. A comparative study between three fresh water algae (Spirogyra sp., Chara sp. and Cladophora sp.) and six marine algae among them brown: Sargassum dentifolium, Padina boryana, Dictyota dichotoma; red: Gelidium latifolium, Gracilaria dura and green: Enteromorpha intestinalis) has been performed to study how marine algae can cope with salinity of seawater. Algal fluorescence from the marine and fresh water groups was analyzed to determine whether differences in room-temperature fluorescence could be ascribed to differences between algal classes or specific for individuals. Results obtained showed that fluorescence signatures were relatively uniform for species within class but were different for different classes. Scanning of the SDS-gel showed the presence of certain characteristic protein banding pattern for each species. The amount of proline showed irregular differences according to species. Mannitol was detected only in the members of brown algae. Moreover, the mineral (sodium and potassium) and glycerol contents of the marine algae has noticeable greater values than those of fresh water members. The expression level of G3PDH mRNA was significantly upregulated in marine algal group as compared to that of the freshwater algae. GPDH had a significant impact on numerous metabolic processes in marine algae, including the biosynthesis of glycerol.

Methyl Jasmonate-Induced Lipidomic and Biochemical Alterations in the Intertidal Macroalga Gracilaria dura (Gracilariaceae, Rhodophyta).

The role of exogenously added methyl jasmonate (MeJA), a lipid-derived signaling compound, in inducing oxidative stress in the marine red macroalga Gracilaria dura was investigated. MeJA at a concentration of 1-100 µM was a strong stimulant of reactive oxygen species (H(2)O(2), HO· and O(2) (·-)) (P < 0.05) causing considerable oxidative stress in G. dura. This further led to lipid peroxidation and degradation of the pigments Chl a and phycocyanin, with a concomitant increase in phycoerythrin. The MeJA-induced oxidative burst also led to the induction of a fatty acid oxidation cascade, resulting in the synthesis of hydroxy-oxylipins and the up-regulation of the 13-lipoxygenase pathway. Electrospray ionization-mass spectrometry-based shotgun lipidomic analysis revealed that monogalactosyldiacylglycerol (a chloroplastic glycerolipid) and phosphatidylcholine (extrachloroplastidic phopholipid) were the most affected lipid classes. The degradation of 18:3-fatty acid-containing monogalactosyldiacylglycerol inferred that it provided fatty acyl chains for the biosynthesis of 13-hydroperoxylinolenic acid, which was further directed towards either the jasmonate pathway or other alternative pathways of the fatty acid oxidation cascade, analogous to higher plants. Also, G. dura modulated the lipid acyl chains in such a way that no significant change was observed in the fatty acid profile of the treated thalli as compared with those of the control, except for C16:0, C16:1 (n-9), C20:3 (n-6) and C20:4 (n-6) (P < 0.05). Furthermore, MeJA caused the accumulation of phenolic compounds and the up-regulation of enzymes involved in secondary metabolism such as polyphenol oxidase, shikimate dehydrogenase and phenylalanine ammonia-lyase, indicating a shift towards secondary metabolism as a defense strategy to combat the induced oxidative stress.

Rapid Screening of Chemical Compositions of Gracilaria dura and Hypnea mucisformis (Rhodophyta) from Corsican Lagoon.

Marine macroalgae are important ecological and commercial biomass resources to many regions of the world. They are valuable food resources and are most promising sources of bioactive compounds for the cosmetic industries. Phytochemical off-line investigation by the separation and identification of secondary metabolites are time, material and human resource consuming. Thus, in our studies, a rapid GC-MS (Gas Chromatography-mass spectrometry) on-line analysis with pretreatment (chemical derivatisations) was adapted for chemical profiling of two wild growing algae: Gracilaria dura and Hypnea mucisformis from Corsica (France). Two GC-MS derivatisation methods were used: transmethylation for the fatty acids (FAs), and trimethylsilylation for compounds which bear -OH/-NH function. The application of the method on Gracilaria dura, and Hypnea mucisformis leads to an identification of FAs, phytosterols, esters, simple phenolic compounds, and sugars from n-pentane, ethyl acetate (EtOAc) and n-butanol (n-BuOH) extracts. This method is quick and low-cost for chemical profiling of marine biomass. It could be applied not only by the fundamental but also cosmetic industrial research. In addition, this study showed that all algae extracts had modest DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activities and the n-BuOH extract of Hypnea mucisformis had a high total phenol content.

Effect of quorum sensing signals produced by seaweed-associated bacteria on carpospore liberation from Gracilaria dura.

Epiphytic and endophytic bacteria associated with green macroalgae Ulva (U. fasciata and U. lactuca) and red macroalgae Gracilaria (G. corticata and G. dura) have been identified from three different seasons to evaluate the effect of quorum sensing (QS) molecules on carpospores liberation from Gracilaria dura. The bacterial isolates belonging to the orders Bacillales, Pseudomonadales, Alteromonadales, and Vibrionales were present in all seasons, whereas Actinomycetales and Enterobacteriales were confined to pre-monsoon and post-monsoon seasons, respectively. Among all the Gram-negative bacteria, seven isolates were found to produce different types of N-acyl homoserine lactones (AHLs). Interestingly, Shewanella algae produced five types of AHL: C4-HSL, HC4-HSL, C6-HSL, 3-oxo-C6-HSL, and 3-oxo-C12-HSL. Subsequently, the AHLs producing bacterial isolates were screened for carpospore liberation from G. dura and these isolates were found to positively induce carpospore liberation over the control. Also, observed that carpospore liberation increased significantly in C4- and C6-HSL treated cystocarps. Sodium dodecyl sulfate and native polyacrylamide gel electrophoresis of the total protein of the C4- and C6-HSL treated cystocarps showed two specific peptide bands of different molecular weights (50 kDa and 60 kDa) as compared to the control, confirming their indirect effect on carpospore liberation.

Feasibility of Gracilaria dura cultivation in the open sea on the Southeastern coast of India

Abstract Gracilaria dura is the industrially potential agarophyte for commercial cultivation in India. Five different cultivation methods namely, floating bamboo raft, poly propylene net, net bag, hanging rope technique and net pouch were investigated for their suitability to undertake farming in the open sea. Among these, polypropylene net method yielded highest biomass (1.764 ± 0.82 kg fr.wt m − 2 ) with corresponding daily growth rate (DGR) of 3.748 ± 0.91% day − 1 , followed by floating bamboo raft (1.05 ± 0.39 kg fr.wt m − 2 , 2.61 ± 0.45% day − 1 ) and net bag (0.904 ± 0.57 kg fr.wt m − 2 , 3.17 ± 1.16% day − 1 ) methods respectively. The projected earnings were higher (US$ 529 month − 1 ha − 1 ) for net method than other techniques tested, which was attributed to low labor requirement, ease of maintenance, and reduced seedling loss coupled with high growth rate.

Cultivation of Gracilaria dura in the open sea along the southeast coast of India

Gracilaria dura is an important red alga having the potential for commercial farming. To cultivate this alga, the floating bamboo raft method was employed. The study was carried out during October 2010 to September 2012 at the southeastern coast of India. The impacts of seasonal variation, initial seed density, harvest period, depth, and epiphyte and epifauna attachment on the raft were analyzed. A clear seasonal trend was observed in the biomass yield in G. dura in this 2-year study. The highest biomass yield (2.01 ± 0.68 kg FW m−2) and daily growth rate (DGR; 3.17 ± 1.71 % day−1) were observed in winter (January to March). ANOVA results also showed no significant variations between DGR and biomass yield between the first and second year (p > 0.05). The algal biomass decreased during summer (April to June) due to high surface seawater temperature and tissue bleaching. Maximum biomass yield and DGR were observed at a low initial seed density of 50 propagules m−2 (2 kg raft−1) with 45 days of culture period. The rafts cultivated in submerged condition showed a high growth rate (2.31 ± 1.35 % day−1); however, it did not vary significantly with cultivation at the surface level. Grazing was observed to be most severe during the months of April to August by selective fishes like Pteroscirtes mitratus, Siganus canaliculatus, Pelates quadrilineatus, and Monodactylus kottelati; the crab Portunus pelagicus; and the isopod Cymodoce truncata. From the 2-year study, it was found that October to March is the ideal period for the large-scale cultivation of this alga.

A green and sustainable approach to utilize bio-ionic liquids for the selective precipitation of high purity agarose from an agarophyte extract

Preferential precipitation of agarose was observed upon addition of choline based bio-ionic liquids in the Gracilaria dura seaweed extract. Choline laurate was found to be the most effective for the work.

Seedling production in the industrially important agarophyte Gracilaria dura (Gracilariales, Rhodophyta)

The commercial exploitation of seaweeds largely depends on success of consistent biomass production. The present study demonstrates technical feasibility for rapid production of viable seedlings clonally through selective propagation of apical fragments of Gracilaria dura. The highest regeneration was recorded at 25 psu salinity, 5 μmol photons m−2 s−1 irradiance and 25 °C where it ranged between 80.83 ± 3.95 and 28.77 ± 2.03 %. The percentage growth in vertical polythene-tube-column culture was ranged between 40.298 ± 27.25 and 55.687 ± 19.39 % and found to be effective in producing large numbers of seedlings. These seedlings showed fast acclimation to outdoor culture and recorded growth rates of 1.37 to 2.25 % day−1 after 1 month. The seedlings grew rapidly when outplanted in open sea with growth rates of 3.06–3.29 % day−1, comparable to commercial farming of Kappaphycus alvarezii along the southeast coast of India. The average length of harvested plants was found to be 7.71 ± 0.89 cm, while fresh weight was 34.60 ± 9.81 g. Further study to understand seasonal variation in regeneration and growth is imperative to scale-up the methodology for year-round production.

Different speciation for bromine in brown and red algae, revealed by in vivo X-ray absorption spectroscopic studies.

Members of various algal lineages are known to be strong producers of atmospherically relevant halogen emissions, that is a consequence of their capability to store and metabolize halogens. This study uses a noninvasive, synchrotron-based technique, X-ray absorption spectroscopy, for addressing in vivo bromine speciation in the brown algae Ectocarpus siliculosus, Ascophyllum nodosum, and Fucus serratus, the red algae Gracilaria dura, G.gracilis, Chondrus crispus, Osmundea pinnatifida, Asparagopsis armata, Polysiphonia elongata, and Corallina officinalis, the diatom Thalassiosira rotula, the dinoflagellate Lingulodinium polyedrum and a natural phytoplankton sample. The results highlight a diversity of fundamentally different bromine storage modes: while most of the stramenopile representatives and the dinoflagellate store mostly bromide, there is evidence for Br incorporated in nonaromatic hydrocarbons in Thalassiosira. Red algae operate various organic bromine stores - including a possible precursor (by the haloform reaction) for bromoform in Asparagopsis and aromatically bound Br in Polysiphonia and Corallina. Large fractions of the bromine in the red algae G.dura and C.crispus and the brown alga F.serratus are present as Br(-) defects in solid KCl, similar to what was reported earlier for Laminaria parts. These results are discussed according to different defensive strategies that are used within algal taxa to cope with biotic or abiotic stresses.

Preparation and functional evaluation of agarose derivatives

ABSTRACTA facile microwave‐assisted one‐pot synthesis of sodium carboxymethylagarose and calcium carboxymethylagarose from Gracilaria dura agarose (Ag) has been described. The process is user friendly, and the highest degree of substitution was obtained within 15 min compared with the conventional method, which requires more than 3 h. Solubility and gelling behavior of the modified Ag products were found to be dependent on degree of substitution of the products. The characterizations were done by using Fourier transform infrared spectroscopy, 1H‐ and 13C‐nuclear magnetic resonance spectroscopy, thermogravimetric analysis, scanning electron microscopy, Inductively coupled plasma spectrophotometry (ICP), rheology, conductometer analysis, and DNA gel electrophoresis. These agarose derivatives were easily soluble in water and exhibited low thermal hysteresis, improved conductivity, and improved the DNA resolution ability of the parent G. dura Ag hydrogels. These hydrogels may have potential applications in the areas including electrochemical devices, microbiology, biomedical, and pharmaceuticals fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40630.

Surfactant-induced coagulation of agarose from aqueous extract of Gracilaria dura seaweed as an energy-efficient alternative to the conventional freeze–thaw process

Surfactant-induced coagulation of agarose from alkali-treated Gracilaria dura seaweed extract (SE) is reported.

Antibacterial activity of marine macroalgae against fish pathogenic Vibrio species

Abstract In mariculture, diseases of microbial origin can cause significant economic losses worldwide; the evolution of microorganism resistance to antibiotics has resulted in a growing need for new antibacterial compounds that are effective in veterinary medicine and characterized by limited undesirable side effects. Increased attention has recently been turned to seaweeds as a promising source for metabolites with antimicrobial activity. Vibriosis is a common disease, caused by bacteria of the genus Vibrio, that can result in high mortality in aquaculture. The aim of this study was to identify seaweeds with antibacterial activity against some pathogenic Vibrio species, in order to identify a possible alternative to the commonly used antibiotics in aquaculture. Chloroform/methanol lipidic extracts of six seaweed species (Chaetomorpha linum, Cladophora rupestris, Gracilaria dura, Gracilaria gracilis, Gracilariopsis longissima, Ulva prolifera) were tested for their antibacterial activities against six fish pathogenic Vibrio species using the disc diffusion method. Different susceptibilities to lipidic algal extracts were observed. All six of the seaweed extracts tested demonstrated inhibition of Vibrio ordalii. The best was that from Gracilariopsis longissima, showing activity against Vibrio ordalii, Vibrio salmonicida, Vibrio alginolyticus and Vibrio vulnificus. The results confirmed the potential use of seaweed extracts as a source of antibacterial compounds or as a health-promoting feed for aquaculture.

Purification and characterization of exo-β-agarase from an endophytic marine bacterium and its catalytic potential in bioconversion of red algal cell wall polysaccharides into galactans

An extracellular exo-β-agarase was characterized from an endophytic bacterial strain Pseudomonas sp. isolated from the red alga Gracilaria dura. The enzyme was purified to homogeneity with a recovery of 28.2% and a purity fold of 8.33. The purified enzyme was composed of single polypeptide with a molecular mass of about 66 kDa. The enzyme exhibited a maximum activity of 81.74 U mL−1 and a specific activity of 615.5 U mg−1. The optimal pH and temperature for its maximum activity were 9.0 and 35 °C respectively. The enzyme stabilized its activity in alkaline pH 7–11 and high salt concentration up to 4 mol dm−3. The enzymatic hydrolyzed product of agar was characterized as neoagarobiose while the bacterium when incubated with G. dura biomass yielded galactose 20% on dry wt basis. The agarolytic ability of the former was further confirmed by release of protoplasts from G. dura tissue through digestion of cell wall polysaccharides. The bacterium investigated in this study could possibly be used for bioconversion of marine red algal polysaccharides into energy feedstock and the purified enzyme for preparation of compounds having pharmaceutical importance.

Synthesis and characterization of agar-based silver nanoparticles and nanocomposite film with antibacterial applications

This study describes the synthesis and characterization of silver nanoparticles and nanocomposite material using agar extracted from the red alga Gracilaria dura. Characterization of silver nanoparticles was carried out based on UV–Vis spectroscopy (421nm), transmission electron microscopy, EDX, SAED and XRD analysis. The thermal stability of agar/silver nanocomposite film determined by TGA and DSC analysis showed distinct patterns when compared with their raw material (agar and AgNO3). The TEM findings revealed that the silver nanoparticles synthesized were spherical in shape, 6nm in size with uniform dispersal. The synthesized nanoparticles had the great bactericidal activity with reduction of 99.9% of bacteria over the control value. The time required for synthesis of silver nanoparticles was found to be temperature dependent and higher the temperature less the time for nanoparticles formation. DSC and XRD showed approximately the same crystalline index (CIDSC 0.73).

Selenium and spermine alleviate cadmium induced toxicity in the red seaweed Gracilaria dura by regulating antioxidants and DNA methylation

The protective role of exogenously supplied selenium (Se) and polyamines (PAs) such as putrescine (Put) and spermine (Spm) in detoxifying the cadmium (Cd) induced toxicity was studied in the marine red alga Gracilaria dura in laboratory conditions. The Cd exposure (0.4 mM) impede the growth of alga while triggering the reactive oxygen species (ROS viz. O(2)(•-) and H(2)O(2)) generation, inhibition of antioxidant system, and enhancing the lipoxygenase (LOX) activity, malondialdehyde (MDA) level and demethylation of DNA. Additions of Se (50 μM) and/or Spm (1 mM) to the culture medium in contrast to Put, efficiently ameliorated the Cd toxicity by decreasing the accumulation of ROS and MDA contents, while restoring or enhancing the level of enzymatic and nonenzymatic antioxidants and their redox ratio, phycobiliproteins and phytochelatins, over the controls. The isoforms of antioxidant enzymes namely superoxide dismutase (Mn-SOD, ~150 kDa; Fe-SOD ~120 kDa), glutathione peroxidase (GSH-Px, ~120 and 140 kDa), glutathione reductase (GR, ~110 kDa) regulated differentially to Se and/or Spm supplementation. Furthermore, it has also resulted in enhanced levels of endogenous PAs (specially free and bound insoluble Put and Spm) and n-6 PUFAs (C20-3, n-6 and C20-4, n-6). This is for the first time wherein Se and Spm were found to regulate the stabilization of DNA methylation by reducing the events of cytosine demethylation in a mechanism to alleviate the Cd stress in marine alga. The present findings reveal that both Se and Spm play a crucial role in controlling the Cd induced oxidative stress in G. dura.

Monitoring horizontal antibiotic resistance gene transfer in a colonic fermentation model

The human microbiota is suggested to be a reservoir of antibiotic resistance (ABR) genes, which are exchangeable between transient colonizers and residing bacteria. In this study, the transfer of ABR genes from Enterococcus faecalis to Listeria monocytogenes and to commensal bacteria of the human gut microbiota was demonstrated in a colonic fermentation model. In the first fermentation, an E. faecalis donor harboring the marked 50-kb conjugative plasmid pRE25(*) and a chromosomal marker was co-immobilized with L. monocytogenes and infant feces. In this complex environment, the transfer of pRE25(*) to L. monocytogenes was observed. In a second fermentation, only the E. faecalis donor and feces were co-immobilized. Enumeration of pRE25(*) and the donor strain by quantitative PCR revealed an increasing ratio of pRE25(*) to the donor throughout the 16-day fermentation, indicating the transfer of pRE25(*) . An Enterococcus avium transconjugant was isolated, demonstrating that ABR gene transfer to gut commensals occurred. Moreover, pRE25(*) was still functional in both the E. avium and the L. monocytogenes transconjugant and transmittable to other genera in filter mating experiments. Our study reveals that the transfer of a multiresistance plasmid to commensal bacteria in the presence of competing fecal microbiota occurs in a colonic model, suggesting that commensal bacteria contribute to the increasing prevalence of antibiotic-resistant bacteria.