Judul: Produksi xilooligozakarida dari xilan tongkol jagung dengan menggunakan xilanase streptomyces sp asal Indonesia
Abstrak: Production of xylanase from three local isolates could be induced with xylan from corncob. The strains of Streptomyces sp. which used in this research are 234P-16 strain, SKK1-8 strain, and 45I-3 strain. Xylanases from strain SKK1-8 and strain 45I-3 showed the higher activity with corncob xylan than oatspelt xylan. The highest xylanase activities for three strains produced from corncob xylan substrate with 1% concentration than 0.5% and 1.5%. Xylanase which produced by Streptomyces sp. is used for hydrolyzing xylan to produce xylooligosaccharide. The product of xylanase hydrolysis could be determined by reducing analysis sugar determination, changing of carbohydrate degree of polymerization (DP), and by Thin Layer Chromatography (TLC). Xylan hydrolysis product from 234P-16 xylanase was long chain xilooligosaccharide on oatspelt xylan and corncob xylan with DP ranging from 83.13 to 20.24. Xylan hydrolysis product SKK1-8 xylanases was short chain xilooligosaccharide with DP ranging from 12.01 to 2.12, and from 45I-3 DP ranging from 5.75 to 2.12 on oatspelt xylan and corncob xylan. The TLC chromatogram showed that hydrolysis product contains various xylooligosaccharides.
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Judul: Penapisan bakteri Xilanolitik dan karakterisasi Xilanasenya untuk hidrolisis tongkol jagung
Abstrak: Hemicellulose is the second largest polysaccharide in nature after cellulose, which consists of xylan as main component. Xylanolitic bacteria produce extracellular enzymes that could hydrolyze agricultural waste, especially xylan-rich materials to xylose and xylooligosaccharides. This research is aimed to screen local isolate xylanolitic bacteria and characterize its enzyme, and then utilize the enzyme for corncob hydrolysis. Seven bacteria isolates (isolates C, F, G, H, J, K1, and P) were selected in this research for its capability to hydrolyze xylan qualitatively and produced high activity enzymes. Enzyme from selected isolate was characterized its optimum pH, substrate specifity, and its stability, and applied it as biocatalyst for corncob hydrolysis. Isolate P was selected as produced high activity enzyme (17.465 nkat/ml) after 7 days fermentation. The enzyme has highest activity on pH 8, corncob as substrate, and stable on temperature of 30oC for 12 hours. Products from enzymatic hydrolysis of corncob after 12 hours were oligosaccharides with DP around 7.
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Judul: Simulasi persamaan keadaan bintang dengan pendekatan klasik dan relativistik
Abstrak: Komposisi bintang yang selalu berubah akanmempengaruhi massa dan radius bintang itu sendiri. Dimana semakin tua sebuah bintang, maka bintang akan didominasi oleh unsur-unsur berat. Dengan persamaan politrop dan metode Runge-Kutta orde 4 didapatkan radius dan massa bintang semakin berkurang seiring berkurangnya nilai Ye, sedangkan kerapatan semakin meningkat. Pendekatan terbaik terdapat pada nilai Ye sebesar 0.5 dimana didapatkan bahwa massa bintang katai putih sebesar 1.4Mo sesuai dengan massa Chandrasekhar dengan radius bintang 5000 km dan nilai kerapatan bintang sebesar 5.31x 106 g cm-3. Untuk massa bintang neutron diperoleh nilai 0.05Modan radius bintang sebesar 2300 km, sedangkan kerapatannya bintang neutron diperoleh sebesar 1.84 x 107 g cm-3 dengan menggunakan pendekatan relativistic. Pendekatan relativistic terbukti lebih baik untuk menentukan radius dan massa bintang, dengan pendekatan terbaik pada nilai Ye sebesar 0.5 yaitu pada bintang katai putih
Keyword: Composition of the stars, density of the stars, mass of the stars, radii of the stars