Now showing items 1-3 of 3

    • Conference paper

      Agar from Gracilariopsis heteroclada from Panay Island, Philippines 

      MTR de Castro - In HP Calumpong & EG Meñez (Eds.), Proceedings of the 2nd RP-USA Phycology Symposium/Workshop, Supplement, 6-10 January 1992, Cebu City, Philippines, 11-18 January 1992, Dumaguete City, Philippines, 1994 - Philippine Council for Aquatic and Marine Research and Development
      This paper aims to determine the optimum NaOH pretreatment strength and duration and also the monthly variations in gel strength, agar yield and sulfate content of agar from Gracilariopsis heteroclada (Zhang et Xia) Zhang et Xia.

      Samples collected from Leganes, Iloilo, Philippines were pretreated with NaOH at different strengths (1,3 and 5%) and duration (30 min and 60 min) at 85-90°C. Agar extractions were done by the method of Nelson et al. (1983) Agar yield was calculated based on Santos (1980). Gel strength and sulfate content were determined using the methods of Aguilar-Santos and Doty (1978) and Jackson and McCandless (1978), respectively. Agar gelling and melting temperatures were analyzed in triplicate (Whyte and Englar, 1976). Viscosity in cps, moisture and ash contents in per percent, were determined using standard methods. Analysis of variance and Duncan’s multiple range test were used to compare the gel strength for the NaOH pretreatment experiment and the different monthly samples. Correlation analysis was carried out to determine the relationship between the different parameters analyzed.

      Highest gel strength (641 gm cm-2 ) and lowest sulfate content (7.66 gm/mg SO4) were obtained following alkaline pre-treatment with 5% NaOH for 30 min with agar yield of 32.4 per cent. Gelling and melting temperatures of agar with the highest gel strength were 40°C and 80°C, respectively, while specific viscosity, moisture and ash contents were 7.5 cps, 12.2% and 4.32%, respectively. Agar yield was negatively correlated with NaOH pre-treatment (P<0.05). Sulfate content was negatively correlated with gel strength (P<0.05).

      Gel strength, agar yield and sulfate content showed monthly variation. Sulfate was highly correlated with gel strength (P<0.05). Agar yield was positively correlated with month, while it is negatively correlated with gel strength (P<0.05).

      The results showed that agar from Gracilariopsis heteroclada has a very good potential for use as raw material for the production of food, drug and industrial grades of agar because of its superior gel strength.
    • Article

      Growth and agar quality of Gracilaria heteroclada (Zhang et Xia) grown in a filter tank 

      MRJ Luhan, F Harder & AQ Hurtado - Philippine Agricultural Scientist, 2006 - College of Agriculture, University of the Philippines Los Baños
      Gracilaria heteroclada Zhang et Xia was grown in filter tanks to determine the growth, agar quality and uptake pattern of nitrogen and to observe the water quality in recirculating water system with seaweed.

      Rapid uptake of nitrogen in G. heteroclada was observed within the first 24th of culture. Filling up of the nitrogen pools in the cell may have continued until the fifth day, the plants started to increase in weight, proportionate to the uptake rate of nitrogen duing the experiment. G. heteroclada stocked at 1 kg m-2achieved a specific growth rate (SGR) of approximately 10.4% d-1 during 15d of culture, at total ammonia-nitrogen and nitrite-nitrogen levels of 0.03-0.27 mg L-1 and 0.04-0.19mg L-1, respectively, in the filter tank. Approximately 11% of nitrogen in the water was removed by the seaweed.
    • Article

      Tank culture of Gracilaria heteroclada (Zhang et Xia) 

      MRJ Luhan, J Tanaka & Y Aruga - Philippine Agricultural Scientist, 2003 - College of Agriculture and Central Experiment Station, University of the Philippines Los Baños
      Culture conditions in tanks were manipulated to improve the growth and agar quality of Gracilaria heteroclada Zhang et Xia. Specific growth rates during culture ranged from -0.51% to 1.40% and gel strength of agar from 439 to 2155 g cm-2. G. heteroclada at a stocking density of 2kg ton-1 and fertilized with ammonium chloride at 40 mg L-1 grew best when water was changed once a month and ammonium chloride was replenished at 20 mg L-1 after water change. When water was not changed, good growth was observed in plants supplied with 1 mg L-1 diammonium phosphate on the 3rd wk of culture.