Judul: Penyiapan Bahan Baku dan Pemanfaatan Ampas Pengolahan Agar- Agar dari Gracilaria verrucosa menjadi Kertas Ramah Lingkungan
Abstrak: Preparation of raw materials for this study begins with the observation of seaweed post harvest activities include harvesting, washing, drying, and packing. Washing and drying is a combined process that most affect the quality of dried seaweed and extracted result. Agar is one of the product from Gracilaria verrucosa with the by-product’s pulp extraction process. The purposes of this study to know the preparation of raw materials, including post-harvest handling as well as physical and chemical properties of Gracilaria verrucosa and increase value-added processing of gelatinous pulp. The gelatinous residue pulp is as raw material for paper making due to its fibrous structure. Seaweed pulp was bleached using H2O2 solution with a concentration of 5% for two hours and then mixed with kaolin, tapioca, cassava, and newsprint with percentage weight 5% and 10% of the total wet weight. Formed pulp printed with size 30 cm x 20 cm. The results showed that the difference in percentage newsprint of weight addition did not significantly affect moisture content, gramatur, and print opacity of the paper. The difference in the percentage of weight increase affects only newsprint paper whiteness.
Keyword: post harvest, Gracilaria verrucosa, agar, paper

Judul: Pemanfaatan Rumput Laut Gracilaria verrucosa Sebagai Produk Bakto Agar dan Aplikasinya Dalam Media Pertumbuhan Mikroorganisme
Abstrak: Gracilaria verrucosa is a kind of seaweed cultivated in brackish water with water salinity of 6-14 ppt. Gracilaria produces a primary compound hydrocoloid metabolite called agarophyt. The aim of this study was to utilize Gracilaria as a bacto agar product with three methods of drying and also to apply bacto agar as a gelling agent in the microbial growth media. The source of Gracilaria sp used in this study was a seaweed that is cultivated by farmers in the village of Langen Sari, Subang. Characterization of raw materials included analysis of moisture content, ash content, protein content, fat content, and carbohydrate content. Acid treatment was carried out before the extraction processing which the acid treatment used of 1% CH3COOH. Temperature and extraction time constant were used at a temperature of 90oC for 45 minutes. Drying methods were done with three, oven dryer, spray dryer, and drum drier. The application of bacto agar as microbial growth media was applying the product by growing yeast and bacteria. Nutrient Agar has been used as a media for the growth of bacteria and Potato Dextrose Agar has been used as a media for the growth of yeast. The inoculation of microbial cultures performed in the plate agar media. In the plate agar media, syneresis occurred when the incubation was accomplished for 48 hours. Therefore additional tests were performed to determine the concentration of the bacto agar to reduce syneresis by testing the addition of gel strength with bacto concentration to 1.5%, 2%, and 2.5%.
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Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model