Judul: Peningkatan Aktivitas Enzim L-Arabinosa Isomerase Dari Geobacillus Stearothermophilus Dengan Teknik Site Directed Mutagenesis
Abstrak: Enzim L-arabinosa isomerase (L-AI) merupakan enzim yang berperan dalam mediasi isomerisasi antara D-galaktosa menjadi D-tagatosa. D-tagatosa, adalah pemanis yang paling mirip dalam rasa dan sifat fisik dengan sukrosa dari seluruh pemanis, selain itu juga dikenal sebagai pengganti gula alami. D-tagatosa merupakan gula langka yang bersifat malabsorbsi atau sulit diserap oleh usus halus. Keunggulan sifat tersebut yang menjadikan D-tagatosa merupakan gula langka dapat dijadikan sebagai salah satu alternatif pengganti sukrosa. Sehingga banyak metode digunakan untuk meningkatkan hasil produksi D-tagatosa dari proses enzimatik L-AI. Produksi enzim L-AI pada umumnya memiliki berbagai kendala, seperti rendahnya aktivitas enzim dari galur murni yang telah diisolasi sebelumnya. Pendekatan rekayasa genetik merupakan alternatif yang dapat dilakukan untuk mendapatkan enzim L-AI dengan aktivitas yang lebih baik, salah satunya adalah dengan melakukan mutasi pada suatu posisi tertentu untuk memperbaiki sifat enzim. Oleh karena itu penelitian ini dilakukan dengan tujuan mengkonstruksi gen araA pada vektor pRHA dan mengekspresikan protein rekombinan L-AI di sitoplasma Escherichia coli serta meningkatkan produksi D-tagatosa dengan berbagai variasi mutasi. Gen penyandi enzim L-AI telah berhasil dikloning ke dalam vektor pRHA, dan diekspresikan di sitoplasma E. coli NiCo21 dengan ukuran protein 57 kDa. Gen tersebut telah berhasil dimutasi dengan menggunakan teknik site directed mutagenesis pada titik mutasi S393T, F280N, F280L dan mutasi ganda S393T-F280L dan S393T-F280N. Lebih lanjut lagi hasil uji aktivitas enzim L-AI dari kelima mutan dan tipe liar, empat diantaranya menunjukkan adanya peningkatan aktivitas enzim L-AI. Mutan S393T memiliki aktivitas spesifik tertinggi yakni 0.518 atau 159% dan diikuti oleh mutan F280L, F280N dan S393T-F280L yakni 24.7%, 15%, dan 14% berturut-turut, dibandingkan dengan tipe liar. Sedangkan penurunan aktivitas enzim ditunjukkan pada mutan S393T-F280N dengan penurunan aktivitas 6% di bandingkan tipe liar. Mutan S393T memiliki nilai untuk dikembangkan di dunia industri.
Keyword: Geobacillus stearothermophilus, L-arabinose isomerase, site directed mutagenesis

Judul: Production and Characterization of an Arabinose Isomerase from Gene of Geobacillus stearothermophilus Local Strain
Abstrak: Arabinose isomerase (AI) is an enzyme that catalyzes isomerization of galactose to tagatose. Besides being used as a low-calorie sweeteners, tagatose has been developed as a functional food because it provides many health benefits such as promoting of weight-loss, anti-halitosis, prebiotic, treating of obesity and reducing in symptoms associated with type 2 diabetes, hyperglycemia, anemia, and hemophilia. Thermostable AIs are potential for tagatose production. AI enzymes encoded by araA gene. The araA gene Geobacillus stearothermophilus originated from Tanjung Api, Poso, Indonesia has been successfully cloned and exspressed at previously study in E. coli BL21 (DE3) pLysS. However expression level of AI still low by SDS-PAGE analysis. The E. coli BL21 was incubated in 37°C at 150 rpm. This research was conducted to optimize the araA gene expression. Result from this research showed that the medium tofu liquid waste consisting yeast extract 0.5% (TLW+YE) increased enzyme productivity. Optimation production was obtained by 16 hours induction. The purification was carried out with three steps of freeze-thaw at -70°C, heat treatment (60°C, 30 minutes) and DEAE ion exchange chromatography (elution buffer 0-1000 mM NaCl). The purified enzyme exhibited optimum activity at 60°C and pH 7. The AI activity in the presence of CaCl2 and MnCl2 was increased to 152% and 563% respectively. Heat stability of enzymes in the presence of CaCl2 and MnCl2 was increased. Half-life (t 1/2) AI in the presence 1 mM of CaCl2 and MnCl2 was increased becomes 301 and 990 minutes respectively.
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Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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