Judul: Isolasi Bakteri Amilolitik Asal Pupa Sutra Attacus atlas dan Karaterisasi Amilasenya
Abstrak: Amylase is one of an enzyme that controls of the world enzyme market, beside it enzyme plays an important role in various industries in Indonesia. The demands of amylase are quite large and have high economic value. Therefore, sources of the enzyme are needed. Microorganism is one of the producer of extracellular enzymes. The materials used in this study were Attacus atlas’s larva and pupas. The purpose of this study was to isolate amilolytic bacteria from Attacus atlas’s larva and pupas, and to characterize the amylase enzyme that is produced by the selected bacterial isolates. Isolation is done by using media that were added inducer of 1% starch. 12 bacteria were obtained from sick pupas, healthy pupas, sick caterpillars and healthy caterpillars, which will be measured amylolytic index. Selected six amylolytic isolates which had the highest index that will used to the next experiment. Isolates USK 1 and 8, had the highest specific enzyme activity that is equal to 0.285 U / mg protein and 0.40 U / mg protein. The result of enzyme characterization showed isolates USK 1 had a temperature optimum at 30°C, pH optimum of 5, with the increased consistency of enzymes, and produced a metaloamilase enzyme. The optimum condition of isolates USK 8 amylase included 30 °C and pH 4. The amylase was catagorised metalloamylase. Identification is only performed on selected isolates the USK 1 using Microgen Bioproduct (physiological testing). The identification of bacterial isolates USK 1 showed that the bacteria is a rod-shaped Burkholderia pseudomallei, which is Gram negative, and pathogenic.
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Judul: Penapisan dan Karakterisasi Amilase dari Bakteri Asal Ekoenzim
Abstrak: Enzim merupakan salah satu produk bioteknologi yang potensial dan akan banyak dimanfaatkan untuk berbagai industri seperti pertanian, pangan, kertas, kertas, tekstil, deterjen dan obat-obatan. Produksi dan perdagangan enzim didominasi oleh kelompok enzim hidrolitik, seperti lipase, protease, katalase, dan amilase. Amilase merupakan salah satu enzim yang paling penting dalam bidang bioteknologi, terhitung dengan produksi amilase yang menyumbang sekitar 25-33% dari produksi enzim di seluruh dunia. Amilase adalah salah satu enzim industri yang sangat umum digunakan untuk menghidrolisis molekul pati menjadi produk sederhana seperti dekstrin, maltosa, glukosa, dan maltotriosa. Oleh karena itu dibutuhkan enzim amilase yang dapat dihasilkan dari bakteri untuk menghasilkan amilase dengan baik serta lebih hemat biaya dengan memanfaatkan limbah rumah tangga salah satunya ialah kulit buah-buahan yang diolah menjadi ekoenzim. Penelitian ini bertujuan menyeleksi bakteri amilolitik yang diisolasi dari ekoenzim, melakukan pemurnian parsial karakterisasi aktivitas enzim amilase, dan identifikasi dari isolat bakteri terpilih. Penapisan bakteri amilolitik dilakukan terhadap 26 isolat bakteri pada media pati. Isolat bakteri amilolitik potensial selanjutnya diamati waktu pertumbuhan dalam memproduksi enzim amilase. Ekstrak kasar enzim dimurnikan dengan fraksinasi amonium sulfat. Fraksi enzim dengan aktivitas tertinggi dikarakterisasi berdasarkan pH dan suhu optimum. Isolat penghasil enzim amilase terpilih diidentifikasi berdasarkan gen 16S rRNA. Isolat bakteri PKL2 menunjukkan aktivitas amilase terbaik yang berhasil ditapis dari 26 isolat bakteri asal ekoenzim dengan nilai indeks amilolitik terbesar yaitu 1,77. Isolat ini tidak dapat melisis sel darah merah, sehingga bukan berpotensi sebagai patogen. Aktivitas amilase PKL2 optimum pada suhu 50ºC dan pH 7,0. Hasil pengendapan enzim dengan 60 % amonium sulfat mampu meningkatkan aktivitas amilase hingga 1,82 kali dari enzim ekstrak kasarnya. Berdasarkan hasil identifikasi spesies menggunakan gen 16S rRNA, menunjukkan isolat PKL2 memiliki kemiripan dengan spesies Bacillus amyloliquefaciens.
Keyword: Amylase activity, Bacillus amyloliquefaciens, eco-enzyme, optimum pH

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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