Judul: Screening of Halophilic and Halotolerant  Protease-producing Microorganisms from the Bima Salt Pond with Krosok Salt  Media
Abstrak: Kebutuhan protease di Indonesia semakin meningkat seiring berjalannya waktu, namun masih bergantung pada impor. Keperluan akan protease tahan garam untuk memenuhi industri tersebut, bisa didapatkan dari mikroorganisme ladang garam. Penelitian ini bertujuan mengisolasi dan mengidentifikasi mikroorganisme halofilik dan halotoleran yang diisolasi dari Ladang Garam di daerah Bima menggunakan media artifisial dengan penambahan garam krosok dari Bima untuk melihat potensi mikroorganisme tersebut sebagai penghasil enzim protease. Metode identifikasi mikroorganisme meliputi isolasi, seleksi isolat proteolitik dengan nilai IP>1, pewarnaan Gram, ekstraksi DNA, amplifikasi, dan sekuensing gen 16S rRNA. Hasil penelitian menunjukkan sebanyak 116 isolat halofilik dan 43 isolat halotoleran berhasil diisolasi pada media dengan penambahan 15%, 20%, dan 5% garam krosok Bima. Sebanyak 28 isolat bersifat proteolitik yang ditandai dengan zona bening pada media susu skim 2%. Identifikasi 8 dari 9 isolat proteolitik terpilih berdasarkan gen 16S rRNA memiliki kemiripan 99%-100%. Isolat BM3-4a, BM4-7a, BM4-2a, BM16-2a, BM4-3a, BM4-4a, dan BM7-2b mirip Halobacillus sp. dan isolat BM4-1a mirip Bacillus sp., The demand for protease in Indonesia is growing steadily, but it was still dependent on imports. The need for salt-resistant protease to fulfill the industry could be obtained from solar salt pond microorganisms. This study aimed to isolate and identify halophilic and halotolerant microorganisms isolated from Salt Ponds in Bima using artificial media with the addition of solar salt from Bima to assess the potential of these microorganisms as protease enzyme producers. Microorganism identification methods included isolation, selection of proteolytic isolates with IP>1 value, Gram staining, DNA extraction, amplification, and 16S rRNA gene sequencing. The results showed that 116 halophilic isolates and 43 halotolerant isolates were successfully isolated on media with the addition of 15%, 20%, and 5% Bima solar salt. A total of 28 isolates were proteolytic characterized by a clear zone on 2% skim milk media. Identification of 8 out of 9 selected proteolytic isolates based on 16S rRNA gene had 99%-100% similarity. Isolates BM3-4a, BM4-7a, BM4-2a, BM16-2a, BM4-3a, BM4-4a, and BM7-2b were similar to Halobacillus sp., and isolate BM4-1a was similar to Bacillus sp.
Keyword: bakteri halofilik, bakteri halotoleran, garam krosok, protease

Judul: Screening of Halophilic and Halotolerant Microorganisms Producing Protease from Lombok Salt Pans Using Solar Salt Medium
Abstrak: Ladang garam merupakan salah satu lingkungan dengan kondisi garam tinggi, menjadikannya habitat potensial bagi mikroorganisme halofilik dan halotoleran. Mikroorganisme ini memiliki kemampuan untuk menghasilkan enzim protease yang penting dalam berbagai aplikasi industri, baik industri pangan maupun non pangan. Penelitian ini bertujuan mengisolasi dan mengidentifikasi mikroorganisme halofilik dan halotoleran penghasil protease dari Ladang Garam Lombok menggunakan media garam krosok. Metode penelitian ini meliputi isolasi mikroorganisme menggunakan media selektif dengan berbagai konsentrasi garam, dilanjutkan dengan uji aktivitas protease melalui metode hidrolisis kasein menggunakan media Skim Milk Agar (SMA) 2%. Hasil penelitian menunjukkan bahwa sebanyak 29 isolat mampu memproduksi enzim protease, di antaranya sembilan isolat menunjukkan aktivitas protease yang tinggi yaitu isolat 1-1a, 1-3b, 7-5b, 20-1a, 21-2a, 22-1a, 22-2a, 22-3a, dan 12-2b dengan rata- rata indeks proteolitik diatas 1,77 (IP = 1,77). Identifikasi molekuler pada gen 16S rRNA menunjukkan bahwa isolat tersebut termasuk dalam genus Planococcus, Exiguobacterium, Thalassobacillus, Halobacillus, dan Bacillus., Salt pans are one of the environments with high salt conditions, making them a potential habitat for halophilic and halotolerant microorganisms. These microorganisms have the ability to produce protease enzymes that are important in various industrial applications, both in the food and non-food industries. This study aimed to isolate and identify halophilic and halotolerant microorganisms producing protease from Lombok Salt Pans using Solar Salt Medium (SSM). The research methods included the isolation of microorganisms using selective media with various salt concentrations followed by the testing of protease activity through casein hydrolysis using 2% Skim Milk Agar (SMA). The results showed that 29 isolates were able to produce protease, with nine isolates exhibiting high protease activity: isolates 1-1a, 1-3b, 7-5b, 20-1a, 21-2a, 22-1a, 22-2a, 22-3a, and 12-2b with an average proteolytic index above 1.77 (PI = 1.77). Molecular identification of the 16S rRNA gene indicated that these isolates belong to the genus Planococcus, Exiguobacterium, Thalassobacillus, Halobacillus, and Bacillus.
Keyword: protease, halofilik, halotoleran, ladang garam, media garam krosok

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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