Judul: dentification of Nitrilase Gene Existence in Soil Sample Using Metagenomic Approach.
Abstrak: Nitrilase merupakan enzim yang berperan dalam biotransformasi senyawa nitril (R-CN) secara langsung, sehingga menghasilkan asam karboksilat dan amonia. Selama dekade terakhir ini, beberapa proses pada bidang farmasi maupun industri mengarah kepada proses biotransformasi dengan enzim nitrilase dibandingkan dengan sintesis kimiawi. Beberapa bakteri yang dilaporkan memiliki enzim nitrilase, antara lain Rhodococcus, Grobacterium, dan Pseudomonas. Penelitian ini bertujuan mengidentifikasi keberadaan gen nitrilase dari sampel tanah dengan pendekatan metagenomik. Tiga bakteri kontrol nitrilase dianalisis dengan metode polymerase chain reaction (PCR) menggunakan primer yang telah didesain (H1F-H1R). Deteksi gen nitrilase dengan menggunakan primer H1F-H1R terhadap ketiga isolat bakteri yang telah terbukti memiliki kemampuan dalam biotransformasi senyawa asetonitril menjadi asam asetat menunjukkan bahwa ketiga isolat bakteri tersebut mengandung fragmen gen nitrilase. Keberadaan gen nitrilase dalam tanah dapat diidentifikasi dengan ekstraksi DNA secara langsung dan amplifikasi gen nitrilase dengan primer H1F-H1R. Hasil analisis dengan BLASTN memperlihatkan bahwa fragmen DNA yang diamplifikasi dengan primer H1F-H1R mempunyai homologi yang tinggi yaitu sebesar 98% terhadap Rhodococcus rhodochrous strain tg1-A6 nitrilase gene. Hasil amplifikasi dan sekuensing fragmen DNA ini menunjukkan bahwa keberadaan gen nitrilase pada sampel tanah dapat diidentifikasi dengan pendekatan metagenomik.
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Judul: Penapisan Bakteri Rhizosfer Padi Penghasil Nitrogenase yang Tahan Kondisi Salin dan Identifikasi Gen nifH
Abstrak: The ability of nitrogen fixing by rhizosfer bacteria could be used to decrease salinity impact in coastal rice field. It was caused by nitrogenase, encoded by nifH gene in component II. The objectives of this research were to screen of rhizosfer bacterias that have the nitrogenase activity in saline condition and identify the presence of nifH gene. The fifty isolates of rhizosfer bacteri isolated from coastal rice field Eretan and Patimban region, West Java was analyzed. Five isolates showed the nitrogenase activity under saline condition, are Er B1 3, Er B1 4, Er B1 9, Er B2 10 dan Ptb B1 4. The identification of nifH gene from these 5 samples using polymerase chain reaction (PCR) showed that the size is ~360 bp. The highest activity of nitrogenase used acetylene reduction assay (ARA) was showed by Er B2 10 is 4,4081 μmol.mL-1hour-1.
Keyword: rhizosfer bacteria, nitrogenase activity, nifH gene, coastal soil, ARA

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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