Evaluation of agar from three species of Gracilaria from Panay and Guimaras islands
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Agar from three species of Gracilaria, G. changii G. coronopifolia, and Gracilariopsis heteroclada, collected form Panay and Guimaras islands was evaluated. Each species was pretreated with NaOH solution before extraction. Highest agar yields were obtained following alkaline pretreatment at the lowest concentration (1% NaOH) for all species. Highest gel strengths were obtained at different alkaline pretreatment conditions: 644 ± 3.4 g cm-2 at 3 % NaOH for 60 min for G. changii, 641 ± 11.9 g cm-2 at 5 % NaOH for 30 min for G. heteroclada, and 170 g cm-2 at 5 % NaOH for 30 min G. coronopifolia. Agar gelling temperatures ranged from 38.5-40ºC and agar melting temperature ranged from 80.5-85 ºC. Specific viscosity was highest for agar from G. changii at 18 cps. Moisture and ash contents ranged from 8.04-15.20 % and 4.32-4.98%, respectively. Based on the result for this study, G. heteroclada and G. changii are two species which merit further studies for their prospective commercial value to the different industries using agar.
Citationde Castro, T. R. (1993). Evaluation of agar from three species of Gracilaria from Panay and Guimaras islands.
PublisherSan Carlos Publications, University of San Carlos
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Monthly variation of agar quality of some gracilarioids from the Philippines (Rhodophyta, Gracilariaceae) MRJ Luhan, MSR Ferrer, J Tanaka & Y Aruga -
The Philippine Scientist, 2004 - San Carlos Publications, University of San CarlosSpecies of the economically important gracilarioid seaweeds from the Philippines were studied to determine the monthly variation in agar quality. Yield, gel strength, melting and gelling temperatures, and sulfate contents were compared. Lowest agar yield was observed in Gracilaria changii in July (4.15%) and highest in Gracilariopsis heteroclada in March (20.84%). Gel strength was lowest in G. heteroclada in November (44 g cm-2) and highest in Gracilaria tenuistipitata in January (874 g cm-2). Melting temperature was lowest in G. heteroclada in November (68.7°C) and highest also in G. heteroclada in January (90.3°C). Gelling temperature was lowest at 34.4°C in G. changii and Gracilaria firma in November and December, respectively; and highest in G. heteroclada in October (45°C). Sulfate content was lowest in G. firma in November (0.16%) and highest in G. heteroclada in February (2.71%). The variation in the agar parameters could be due to different composition of agars of different species. Sulfate is significantly lower in Gracilaria firma. Yield is significantly higher in Gracilariopsis heteroclada. There is no significant difference in the gel strength, melting and gelling temperatures among species.
Conference paperAQ Hurtado-Ponce - In TU Bagarinao & EEC Flores (Eds.), Towards sustainable aquaculture in Southeast Asia and Japan: Proceedings of the Seminar-Workshop on Aquaculture Development in Southeast Asia, Iloilo City, Philippines, 26-28 July, 1994, 1995 - SEAFDEC Aquaculture DepartmentResearch on seaweeds focused on the carrageenan-producing Kappaphycus alvarezii and the agar-producing Gracilaria spp. Growth of K. alvarezii was better on horizontal lines than on vertical or cluster lines from bamboo rafts. All morphotypes (brown green, and red) grew faster at 50 cm than at 100 cm below the water surface, but the green morphotype showed better carrageenan properties. A socioeconomic survey of K. alvarezii farming in Panagatan Cays, Antique revealed that a farmer has an average annual production of 3 tons/ha (dry) with the fixed bottom and hanging longline methods. Three species of Gracilaria in natural beds in lloilo showed monthly variations in biomass and agar quality; G. heteroclada had the highest biomass and gel strength. When this species was grown in tanks, growth and agar sulfate content were influenced by the interaction of light, salinity, and nutrients. Enriched and unenriched stocks of G. heteroclada differed in agar quality. When G. heteroclada was grown with the tiger shrimp Penaeus monodon in extensive ponds, the highest growth rate and production were obtained at the seaweed stocking density of 250 g/m2; this was in November when average water temperature, transparency, and salinity were low. Salinity tolerance varies among Gracilaria species.Oyster (Crassostrea iredalei) and mussel (Perna viridis) farming in Western Visayas were assessed in 1992 in terms of the culture methods, socioeconomics, marketing, and profitability. A more localized survey of oyster and mussel fanning was conducted through rapid rural appraisal in two coastal towns in 1993. A farmer-participatory study followed in 1994 for the culture of oysters, mussels, seaweeds, and rabbitfishes in a river mouth in Dumangas, lloilo. Green mussel, brown mussel (Modiolus metcalfei), and seaweeds transplanted to Dumangas from Capiz have reproduced. In another study, the green mussel was tested as a biological filter in tiger shrimp ponds; shrimps stocked with mussels grew better than those without. A nationwide survey on the Placuna placenta fishery in 1993 showed 27 remaining 'kapis' beds; many others have been depleted due to excessive gathering, pollution, siltation, and trawling. Broodstocks are being developed to produce 'kapis' seed for grow-out and restocking. For the first time at AQD, adult donkey-ear abalone Haliotis asinina from the wild spawned naturally in laboratory tanks. Juvenile abalones can be successfully grown on Gracilaria or abalone diet.
Carpospore germination and early stages of development in Gracilaria edulis (Gmelin) Silva and Gracilaria rubra Chang et Xia (Gracilariales, Rhodophyta). AQ Hurtado-Ponce -
The Philippine Scientist, 1993 - San Carlos Publications, University of San CarlosCarpospore germination and early stages of development in Gracilaria edulis and Gracilaria rubra of the Philippines are described for the first time. Both species follow the "Dumontia type" or the immediate discal type of growth. Young plants with secondary branches were observed after 17 days of germination.