Judul: Character of Bacillus spp. as probiotic
Candidates for Cats
Abstrak: Upaya pencegahan penyakit pencernaan dan peningkatan laju pertumbuhan pada kucing dapat dilakukan dengan aplikasi probiotik sebagai pengganti antibiotik. Bakteri Bacillus spp. sebagai kandidat probiotik akan menguntungkan karena memiliki spora yang dapat bertahan hidup pada kondisi ekstrem dan memiliki umur simpan yang panjang. Penelitian ini bertujuan mengarakterisasi Bacillus spp. sebagai kandidat probiotik untuk kucing. Parameter seleksi bakteri kandidat probiotik meliputi sifat toleran terhadap asam lambung dan garam empedu serta aktivitas enzim protease. Sebanyak 5 isolat yang diisolasi dari sampel feses kucing dan 2 isolat dari sampel usus ikan lele merupakan bakteri Gram postif dan berbentuk batang. Isolat BB 3.2, STB 1.6, dan PTB 1.7 memiliki sifat toleran pada lingkungan yang mengandung asam pH 2,5 dan garam empedu 0,3%. Isolat STB 1.6 memiliki aktivitas enzim protease paling tinggi berdasarkan diameter zona bening yang terbentuk pada media susu skim 3%. Isolat STB 1.6 dapat tumbuh pada media yang mengandung10% pakan kucing setelah diinkubasi selama 24 jam. Bakteri isolat STB 1.6 memiliki kemiripan dengan bakteri Priestia qingshengii., Efforts to prevent digestive diseases and increase growth rates in cats can be made by applying probiotics as a substitute for antibiotics. Bacillus spp. as a probiotic candidate will be advantageous because it has spores that can survive extreme conditions and have a long-term shelf life. This study aims to characterize Bacillus spp. as a candidate probiotic for cats. The method for selecting probiotic candidate bacteria is that the bacteria are tolerante to stomach acid and bile salts and have protease enzyme activity. A total of 5 isolates isolated from cat feces samples and 2 isolates from catfish intestine samples were Gram positive and rod-shaped bacteria. Isolates BB 3.2, STB 1.6, and PTB 1.7 tolerante environments containing acid pH 2.5 and bile salts 0.3%. The STB 1.6 isolate had the highest protease enzyme activity based on the diameter of the clear zone formed in 3% skim milk media. The STB 1.6 isolate grown in 10% cat food media experienced an increase in the log number of bacterial cells after being incubated for 24 hours. The STB 1.6 isolate bacteria is similar to the Priestia qingshengii bacteria.
Keyword: antibiotik, asam lambung, garam empedu, Priestia qingshengii, antibiotic, bile salt, stomach acid

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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