Judul: Optimasi Media Produksi untuk Kandidat Probiotik Bacillus sp. Isolat PTC 1.4
Abstrak: Bakteri probiotik sudah umum digunakan dalam budidaya hewan terestrial sebagai suplemen makanan untuk meningkatkan kelangsungan hidup. Oleh karena bakteri probiotik memiliki manfaat yang melimpah, maka harus dapat dihasilkan dalam jumlah banyak menggunakan bahan yang lebih ekonomis sehingga dapat menekan biaya produksi, salah satunya adalah tempe. Parameter yang diuji dalam penelitian ini adalah jumlah bakteri total dan produksi enzim protease untuk mengetahui bakteri masih dapat menghasilkan enzim tersebut. Tujuan penelitian ini yaitu memperoleh komposisi media produksi yang optimum dengan bahan dasar tempe untuk bakteri probiotik Bacillus sp. Penelitian diawali dengan peremajaan isolat bakteri, perbanyakan kultur, pembuatan media tumbuh berupa media Tryptone Soy Broth (TSB) dan dua media racikan tempe, uji pertumbuhan bakteri, dan uji aktivitas enzim protease secara kualitatif. Hasil penelitian menunjukkan bahwa penggunaan tempe memberikan pertumbuhan bakteri Bacillus sp. lebih maksimal dibandingkan penggunaan media TSB. Laju pertumbuhan spesifik maksimum bakteri yang ditumbuhkan dalam media tempe juga memiliki nilai yang lebih tinggi dibandingkan dengan media TSB. Nilai indeks proteolitik bakteri pada media racikan memberikan hasil yang serupa dengan media TSB., Probiotic bacteria are commonly used in cultivating terrestrial animals as food supplements to increase survival. Probiotic bacteria have abundant benefits, therefore they must be produced in large quantities using ingredients that are more economical so that they can reduce production costs, one of which is tempeh. Parameters to be tested in this study were the total number of bacteria and the production of protease. The aim of this research is to obtain the optimum composition of production media with tempeh as the basic ingredient for Bacillus sp. The research began with rejuvenation of bacterial isolates, culture multiplication, making growth media such as Tryptone Soy Broth (TSB) media and two tempeh media, bacterial growth, and qualitative protease enzyme activity tests. The results of the study show that tempeh can promote the growth of Bacillus sp. optimally than using TSB media. The maximum specific growth rate of bacteria grown in tempeh media also had a higher value compared to TSB media. The proteolytic index value of bacteria in tempeh media gave similar results to the TSB media.
Keyword: Environmentally friendly, Media formulation, Protease, Tempeh

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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