National Committee on Marine Sciences (NCMS)
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- Seasonal variations in the yield, gelling properties, and chemical composition of agars from Gracilaria eucheumoides and Gelidiella acerosa (Rhodophyta) from the PhilippinesVillanueva, R. D.; Montaño, N. E.; Romero, J. B.; Aliganga, A. K. A.; Enriquez, E. P. (Walter de Gruyter GmbH, 1999-01-01)The yield, physical, and chemical properties of agars from two Philippine red seaweeds, Gracilaria eucheumoides and Gelidiella acerosa, were investigated on a bimonthly basis. The yield of agar from Gracilaria eucheumoides was at a maximum during the early rainy season (May, 29%) and at a minimum during the summer month of March (20%). In Gelidiella acerosa, a peak in agar yield was also recorded in May (21%), with generally higher yields recorded during the rainy than in the dry season. Agar gel strengths fluctuated from 225 to 430 g cm−2 and from 160 to 820 g cm−2 for Gracilaria eucheumoides and Gelidiella acerosa, respectively, and both agars exhibited strongest gels in July. Significant seasonal variations were observed in the gelling and melting temperatures of agar from Gracilaria eucheumoides, but not from Gelidiella acerosa. Sulphate content only varied slightly in agar samples from Gracilaria eucheumoides, while a higher sulphate content was found in Gelidiella acerosa agar during the dry season. Moreover, the sulphate content in G. acerosa agar fluctuated inversely with the 3,6-anhydrogalactose content. A FT-IR analysis showed a fairly constant spectrum for temporal Gracilaria eucheumoides agar while peaks attributed to S–O vibrations intensified in Gelidiella acerosa samples which were recorded to contain high sulphate residues and possess low gel strengths. Diagnosis of the FT-IR spectra in the 1000–400 cm−1 frequency range was also conducted in comparison with agarose and Gracilaria chilensis agar.
- Highly methylated agar from Gracilaria edulis (Gracilariales, Rhodophyta)Villanueva, Ronald; Montaño, Nemesio (Springer, 1999-04)The structure and gelling properties of alkali-modified agar from Gracilaria edulis were investigated. 1H and 13C NMR experiments revealed a basic repeating unit of alternating 3-linked 6- O-methyl-β-D-galactopyranose and 4-linked 3,6-anhydro-α-L-galactopyranose. Partial methylation at O-2 of the anhydrogalactose moiety was also revealed. Meanwhile, the O-4 of the methylated galactose residue was detected to exhibit partial sulfation by NMR and FT-IR spectroscopy. The gel strength and syneresis index of the extracted agar were considerably enhanced by the addition of sodium, potassium, and calcium ions. The ion-driven gelation and peculiar sulfate position conferred the agar's similarity to κ-carrageenan.
- Chemical characteristics and gelling properties of agar from two Philippine Gracilaria spp. (Gracilariales, Rhodophyta)Montaño, Nemesio E.; Villanueva, Ronald D.; Romero, Jumelita B. (Springer, 1999)The chemical structure of agars extracted from Philippine Gracilaria arcuata and G. tenuistipitata were determined by NMR and infrared spectroscopy. Agar with alternating 3-linked 6-O-methyl-β-D-galactopyranosyl and 4-linked 3,6-anhydro-2- O-methyl-α-L-galactopyranosyl units was isolated from G. arcuata, while the agar from G. tenuistipitata possesses the regular agarobiose repeating unit with partial methylation at the 6-position of the D-galactosyl residues. Both agars exhibit sulphate substitution at varying positions in the polymer. Chemical analyses reveal higher 3,6-anhydrogalactose and lower sulphate contents in alkali-modified than in native agar from both samples. Also, alkali modification enhanced agar gel strength and syneresis. Native G. arcuata agar produces a viscous solution (2000 cP at 75 °C) with a high gelling point (>60 °C) that forms a soft gel even after alkali modification (gel strength: <300 g cm−2). On the other hand, the agar from G. tenuistipitata exhibits gel qualities typical of most Gracilaria agars.
- Karyology and agar analysis of the agarophyte Gelidiella acerosa (Forsskål) Feldmannet Hamel from the PhilippinesKapraun, Donald F.; Ganzon-Fortes, Edna; Bird, Kimon T.; Trono, Gavino; Breden, Chris (Springer, 1994-12)Microspectrophotometry with the DNA-localizing fluorochrome DAPI demonstrated ploidy level differences in tetrasporophytic and presumptive gametophytic phases of Gelidiella acerosa from the Philippines. Comparison of mean nuclear DNA (I f ) values to chicken erythrocytes (RBC) resulted in an estimate of 0.32 pg/2 C genome. Karyological studies with aceto-orcein revealed a chromosome complement of six bivalents during diakinesis of tetrasporocytes. The agar yield ranges from 13–24% dry weight, depending on the method of extraction. Agar extraction in 1 N NaOH resulted in an increased gel strength of 189 g cm−2 at 1.5% concentration. Infrared spectroscopy indicated a relatively high sulfate content in native agar. The low (61 °) melting temperature is indicative of high sulfation and small molecular size.
- Quantification and characterization of nuclear genomes in commercial red seaweeds (Gracilariales) from the PhilippinesKapraun, Donald F.; Lopez-Bautista, Juan; Trono, Gavino; Bird, Kimon T. (Springer, 1996-03)Eight species of Gracilariaceae from the Philippines, representing the genera Gracilaria, Gracilariopsis and Hydropuntia, were investigated to quantify and characterize their nuclear genomes. DNA reassociation kinetics were used to determine nuclear genome organization and complexity in six of these species. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–74% and unique DNA ranged from 26–84%. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA contents. Comparisons of mean nuclear DNA (I f ) values to chicken erythrocytes (RBC) resulted in an estimate of 0.38–0.43 pg/2 C genomes for seven of the species investigated. Preliminary analyses of agar content and quality confirm the economic potential of Gracilaria firma, Gracilaria sp. 2 from Sorsogon and Gracilariopsis bailinae. Nuclear genome profiles developed from data for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity.
- Zamboanga stakes claim as RP’s top seaweed producer(Philippine Star Printing Co., Inc., 2008-03-23)In the face of declining seaweed harvests in the country’s traditional major seaweed production centers, the regional office of the Bureau of Fisheries and Aquatic Resources (BFAR) in Region IX has taken bold steps to intensify seaweed culture in the whole Zamboanga Peninsula. “The objectives,” says BFAR Region IX director Virgilio Alforque, “are to help stabilize seaweed supply in the country, enable seaweed processors to operate at higher capacity and, most importantly, make it possible for Zamboanga’s seaweed farmers to take advantage of prevailing high prices.” Fortunately, a new research by SEAFDEC researchers Anicia Hurtado and Renato Agbayani has shown that deep water (more than 10 meters deep) farming of the seaweeds Kappaphycus is possible and very profitable just like the other methods in shallower waters. This method in deeper waters is commonly called alul.