Judul: Karakterisasi Enzimatik Probiotik Bacillus cereus BR2 dan Pola  Pertumbuhan di Berbagai Media Alternatif
Abstrak: Probiotik memiliki peranan yang sangat penting dalam bidang akuakultur. Efektivitas penggunaan bakteri probiotik sangat dipengaruhi oleh jenis bakteri yang digunakan. Salah satu jenis bakteri Bacillus yang potensial digunakan sebagai probiotik ialah Bacillus cereus BR2. Penelitian ini bertujuan mengidentifikasi kemampuan enzimatik probiotik B. cereus BR2, mengevaluasi pertumbuhan sel dalam media kultur masal dengan menggunakan media alternatif serta menguji keamanan aplikasi bakteri probiotik B. cereus BR2 terhadap tingkat kelangsungan hidup Artemia dengan uji bioassay. Penelitian dilakukan secara in vitro dan bioassay. In vitro yaitu menumbuhkan bakteri pada media yang mengandung TSB, kaldu daging, molase, tepung tapioka, dan kombinasinya. Bioassay yaitu penambahan TSB, kombinasi kaldu daging, molase, dan tepung tapioka pada media pemeliharaan Artemia yang diberi bakteri probiotik B. cereus BR2, yang meliputi tiga perlakuan yakni: perlakuan kontrol negatif tanpa penambahan bakteri maupun bahan (K-), penambahan TSB 0,1% dan bakteri (K+), penambahan kaldu daging 0,1%, molase 0,1%, tepung tapioka 0,1% dan bakteri (ABC). Parameter yang diamati pada penelitian ini adalah uji enzimatik pada isolat bakteri probiotik B. cereus BR2 secara kualitatif, uji pertumbuhan probiotik B. cereus BR2 di berbagai jenis media alternatif, analisa kurva tumbuh B. cereus BR2 OTCR pada media optimum, kualitas media kultur, dan survival rate (SR) Artemia. Hasil menunjukkan bahwa isolat Bacillus cereus BR2 mempunyai aktivitas enzimatik berupa proteolitik, amilolitik, dan lipolitik. Media kultur alternatif yang optimum bagi pertumbuhan isolat bakteri probiotik B. cereus BR2 OTCR yaitu terdapat pada media dengan kombinasi bahan berupa kaldu daging 0,1% (v/w) molase 0,1% (v/w) dan tepung tapioka 0,1% (w/w). Pada perlakuan penambahan kaldu daging 0,1%, molase 0,1%, tepung tapioka 0,1% dan bakteri B. cereus BR2 (ABC) dengan uji bioassay menggunakan Artemia sebagai hewan uji coba didapatkan nilai kelangsungan hidup berkisar antara 83,33±1,00% – 97,78±1,15% dan berbeda nyata dengan perlakuan K+ dengan nilai kelangsungan hidup berkisar antara 55,56±3,51% – 90,00±1,00%., Probiotics have a very important role in the field of aquaculture. The effectiveness of using probiotic bacteria is strongly influenced by the type of bacteria used. One type of Bacillus bacteria that has the potential to be used as a probiotic is Bacillus cereus BR2. This study aims to identify the enzymatic ability of the B. cereus BR2 probiotic, evaluate cell growth in mass culture media using alternative media and tested the safety of the application of B. cereus BR2 probiotic bacteria on the survival rate of Artemia by bioassay test. The research was conducted in vitro and bioassay. In vitro, namely growing bacteria on media containing TSB, meat broth, molasses, tapioca starch, and their combinations. The bioassay was the addition of TSB, a combination of meat broth, molasses, and tapioca flour to the Artemia rearing medium supplemented with the probiotic bacteria B. cereus BR2, which included three treatments namely: negative control treatment without the addition of bacteria or ingredients (K-), addition of TSB 0, 1% and bacteria (K+), addition of 0.1% meat broth, 0.1% molasses, 0.1% tapioca flour and bacteria (ABC). Parameters observed in this study were enzymatic tests on probiotic bacteria B. cereus BR2 isolates qualitatively, growth tests of B. cereus BR2 probiotics in various types of alternative media, analysis of the growth curve
Keyword: enzymatic activity, Bacillus cereus BR2, alternative media, probiotics

Judul: Isolation and Selection of Bacillus spp. as Probiotic Candidates for Broiler Chickens.
Abstrak: Upaya peningkatan laju pertumbuhan ayam dapat dilakukan melalui aplikasi probiotik sebagai pengganti antibiotik. Probiotik dari Bacillus spp. memiliki spora yang stabil dalam jangka waktu lama pada produk komersial. Penelitian ini bertujuan mengisolasi dan menyeleksi Bacillus spp. asal tanah Jasinga sebagai kandidat probiotik pada ayam. Isolasi dilakukan dengan perlakuan panas sampel tanah pada suhu 80 oC selama 20 menit dan dilakukan pengamatan secara makroskopis dan mikroskopis. Metode selanjutnya meliputi uji hemolisis, aktivitas enzim protease, amilase, selulase, ketahanan garam empedu, uji antagonistik, sensitivitas antibiotik dan hidrofobisitas permukaan sel. Sebanyak 15 isolat berhasil diisolasi dari tanah asal Jasinga, dan 12 isolat berdasarkan pengamatan mikroskopik merupakan Bacillus spp. Sebanyak 6 isolat memiliki aktivitas gamma hemolisis dan memiliki kemampuan menghidrolis protein, pati, dan selulosa yang beragam. Isolat BTJ1.1, BTJ1.2, BTJ1.4, dan BTJ2.3 mengalami peningkatan jumlah log sel isolat pada lingkungan yang mengandung garam empedu 0,3%. Isolat BTJ1.1, BTJ1.2, dan BTJ2.3 mengindikasikan adanya aktivitas antimikroba, dan memiliki sifat yang sensitiv terhadap amoxicillin, tetracycline, rifampicin, namun ke empat isolat memiliki sifat yang resisten terhadap chloramphenicol. Kesimpulan penelitian ini menunjukkan bahwa BTJ1.1 dan BTJ2.3 merupakan isolat terbaik yang berpotensi sebagai kandidat probiotik., Efforts to improve the growth rate of chickens can be achieved through the application of probiotics as an alternative to antibiotics. Probiotics derived from Bacillus spp. have spores that remain stable for extended periods in commercial products. This study aims to isolate and select Bacillus spp. from Jasinga soil as probiotic candidates for chickens. Isolation was carried out by subjecting the soil samples to heat treatment at 80 °C for 20 minutes, followed by macroscopic and microscopic observations. The next methode included hemolysis tests, protease, amylase, and cellulase enzyme activities, bile salt tolerance, antagonistic assays, antibiotic sensitivity, and cell surface hydrophobicity. A total of 15 isolates were successfully isolated from Jasinga soil, and based on microscopic observations, 12 isolates were identified as Bacillus spp. Six isolates exhibited gamma hemolysis activity and displayed diverse abilities to hydrolyze proteins, starch, and cellulose. Isolates BTJ1.1, BTJ1.2, BTJ1.4, and BTJ2.3 showed increased cell numbers an environment containing 0,3% bile salt. Isolates BTJ1.1, BTJ1.2, and BTJ2.3 indicated antimicrobial activity and were found to be sensitive to amoxicillin, tetracycline, and rifampicin, while all four isolates were resistant to Chloramphenicol. The conclusion of this research that BTJ1.1 and BTJ2.3 are the best isolate as potential probiotic candidate.
Keyword: antibiotics, bile salt, hydrolytic index, resistance, soil

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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