Judul: Genome Shuffling Lactobacillus rhamnosus dan Lactobacillus pentosus sebagai Fusant Penghasil L-Lactic Acid
Abstrak: Asam laktat terutama isomer L-lactic acid merupakan salah satu bahan tambahan pangan yang cukup luas penggunaannya, yakni sebagai perisa, pengatur keasaman dan penyusun plastik polylactic acid. Asam laktat umumnya diproduksi secara fermentasi menggunakan bakteri asam laktat. Limbah industri pangan yang mengandung hemiselulosa masih cukup melimpah sementara pemanfaatannya belum optimal. Salah satu gula hasil hidrolisis hemiselulosa adalah gula xilosa. Xilosa dapat dimanfaatkan bakteri asam laktat (BAL) seperti Lactobacillus pentosus untuk menghasilkan asam laktat. Kelemahan bakteri ini adalah asam laktat yang dihasilkan masih berupa campuran L- dan D-lactic acid. Oleh karena itu diperlukan perbaikan sifat genetik supaya asam laktat yang dihasilkan hanya L-lactic acid yakni dengan cara genome shuffling Lactobacillus pentosus dengan Lactobacillus rhamnosus. Hasil yang diharapkan dari penggabungan keduanya adalah strain baru yang mampu menggunakan xilosa sebagai subtrat dan menghasilkan produk utama berupa Llactic acid. Keunggulan genome shuffling dibandingkan rekayasa genetika secara konvensional adalah pengerjaan lebih sederhana, waktu yang dibutuhkan relatif lebih singkat serta tidak memerlukan peta genetik bakteri secara lengkap. Penelitian ini bertujuan untuk memperoleh waktu inkubasi optimal pembentukan protoplas Lactobacillus rhamnosus dan Lactobacillus pentosus serta memperoleh strain bakteri asam laktat (fusant antara Lactobacillus rhamnosus dan Lactobacillus pentosus) yang mampu menggunakan xilosa sebagai substrat dan mampu memproduksi L-lactic acid dengan menggunakan teknik genome shuffling. Penelitian terdiri dari penentuan waktu optimal pembentukan protoplas dan genome shuffling. Hasil penelitian menunjukkan bahwa kondisi optimal pembentukan protoplas L. rhamnosus adalah dengan menggunakan konsentrasi lisozim 10 mg/ml ( 200 000 U/ml) waktu inkubasi selama 2 jam sedangkan untuk L. pentosus dengan konsentrasi lisozim > 5 mg/ml (100 000 U/ml) dan waktu inkubasi 2 jam. Pada penelitian ini telah berhasil diperoleh 16 fusant yang mampu menggunakan xilosa untuk dikonversi menjadi L-lactic acid.
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Judul: Seleksi dan Optimasi Bakteri Asam Laktat Penghasil Senyawa Antikapang
Abstrak: Silage is the forage preservation product through anaerobic fermentation by using lactic acid bacteria (LAB). The presence of oxygen may activate the other microbe that could be contaminate and interrupt the silage processing. Fungi is a microbe that often contaminate silage processing. In Indonesia, prevention of silage contamination by fungi is necessary in order to support livestock business. By using the inoculum that able to produce antifungal compounds, the fungi contamination could be prevented. This research was dedicated to screen LAB having antifungal properties, taxonomic study and optimization of antifungal production. Screening of antifungal producing LAB was initiated by growing LAB on de Man Rogosa Sharpe Agar (MRSA) against Aspergillus fumigatus, A. flavus, and Penicillium by plate assay method (aerobic condition) and verified by deep tube technique (anerobic condition). The results showed that strain DR 1-6-2 could inhibit A. fumigatus and A. flavus in aerobic condition with percentage of inhibition was 41% and 32 %, respectively. In anaerobic condition, strain DR 1-6-2 could inhibit not only A. fumigatus, A. flavus, but also Penicillium. Identification of selected LAB was carried out using 16S rRNA gene sequencing with 27F and 1492R primer. Based on molecular analysis, strain DR 1-6-2 is belong to Lactobacillus plantarum with the degree of homology of 98%. Optimization of antifungal production by selected LAB was carried out using Response Surface Method (RSM) with Central Composite Design (CCD) on five variables (glucose, yeast extract, CH3COONa, K2HPO4, Tween 80) and five level combinations. From statistical analysis, the production of antifungal which is represented by the total lactic acid production of selected LAB is significantly influenced by glucose, combination of glucose and K2HPO4, combination of yeast extract and K2HPO4 and Tween 80. The optimum concentration of glucose is 2.91%, yeast extract 0.58%, K2HPO4 0.29% and Tween 80 0.19% with a maximum predicted lactic acid yield of 2.61%, which is increased by 59%. This result is confirmed when the optimum concentration of nutritions used. The production of lactic acid increased by 58%. Benefit of this research is utilization of indegenous LAB isolates as the silage inoculum and antifungi to prevention of contamination and to obtain a good silage quality. This LAB utilization is capable to trigger the silage production, which in turn could increase the silage utilization as animal feed, increasing the production of meat, and could support the government's efforts to achieve the national demand of meat product. In silage fermentation using L. plantarum DR 1-6-2, anaerobic condition is a requirement to be considered. Identification of other antifungal compounds produced by L. plantarum DR1-6-2 is need to be studied.
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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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