Gold-modified boron doped diamond (BDD) electrodes were examined for the amperometric detection of oxygen as well as a detector for measuring biochemical oxygen demand (BOD) using Rhodotorula mucilaginosa UICC Y-181. An optimum potential of -0.5 V (vs Ag/AgCl) was applied, and the optimum waiting time was observed to be 20 min. A linear calibration curve for oxygen reduction was achieved with a sensitivity of 1.4 μA mg(-1) L oxygen. Furthermore, a linear calibration curve in the glucose concentration range of 0.1-0.5 mM (equivalent to 10-50 mg L(-1) BOD) was obtained with an estimated detection limit of 4 mg L(-1) BOD. Excellent reproducibility of the BOD sensor was shown with an RSD of 0.9%. Moreover, the BOD sensor showed good tolerance against the presence of copper ions up to a maximum concentration of 0.80 μM (equivalent to 50 ppb). The sensor was applied to BOD measurements of the water from a lake at the University of Indonesia in Jakarta, Indonesia, with results comparable to those made using a standard method for BOD measurement.

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The brown seaweed Sargassumsp. is well known as a source of fucoidan. Brown seaweeds found in Indonesia seas are dominated by Sargassum sp.The objectives of this research was to purify and characterize fucoidan from S. binderi Sonder. The fresh raw material was defatted by macerated in methanol:chloroform:water (4:2:1), filtered, rinsed with acetone and then air-dried in room temperature. The defatted dried seaweed was extracted with 0.01M HCl pH 4 at room temperature. Purification has been conducted using anion exchanger. The quality of fucoidan sample was determined for total sugar, functional group using FTIR, monomer content, total ash, and total sulfate in the ester form. The result shows that pure fucoidan contains fucose as the primary sugar component, and otherminor sugars (galactose, glucose, mannose and xylose). Chemical composition of crude fucoidan consisted of 74.25% fucose; 0.28% uronate acid; 10.29% sulfate and 5.5% protein. Purification using DEAE Sephadex A-25 gave 4 fraction pools yielding total sugar (%) of F1 (17.59); F2 (18.92); F3 (13.72); F4 (49.76), respectively. The components that build the fucoidan of S. binderi Sonder were estimated derived to be from fucoidan oligomers including (1,4)-L-FucS-Gal and D-(1,4)-Gal-GalS.

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Fucoidan used as immunostimulant is commonly in the crude form. In this study, we investigated the effect of fucoidan in both crude and purified forms in their immunostimulatory activity. In addition, we studied the effect of low-and high-molecular weight fucoidan as hydrolysis products toward immunostimulatory activity. Four kinds of fucoidan were assayed for immunostimulant activity on the shrimp Litopenaeus vannamei. The parameters observed in the assay includes the mortality number, haemocyte, gene-related immunity (phenoloxidase, superoxide dismutase and transglutaminase) in the shrimps infected with viral WSSV. The assay results showed that pure fucoidan exhibited higher activity compared with that of crude fucoidan. Sulfate and carbohydrate content of HMW fucoidan are 7.8 % and 82.54 % with an estimated molecular weight of 8.28 x10 4 Dalton, and low molecular weight (LMW) fucoidan has 1.2% and 65.23% with an estimated molecular weight of 7.53 x10 4 Dalton. The transcriptional level of the immunity-related genes was found higher after feeding the infected shrimps with purified and HMW fucoidan. In particular, all of fucoidan forms increased the phenoloxidase gene transcription, suggesting that fucoidan have significant role in the production of phenoloxidase.

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