Judul: Potensi Daya Hambat Bakteri Asam Laktat terhadap Cendawan pada Dangke Selama Penyimpanan
Abstrak: Dangke is a traditional dairy product in Enrengkang District, South Sulawesi. Since dangke is produced traditionally in small scale unit (home industry) the microbial contamination of dangke is critical point in food quality and safety, specifically the fungal contamination of fungi. It is necessary to develop a method to inhibit growth of fungi in dangke. Lactic acid bacteria (LAB) could be a potential biopreservative of dangke regarding to inhibition of fungal contamination. The aim of this research was to review the effectiveness of inhibition of LAB against fungi in dangke during storage. The study was devided into three steps, i.e., observation of fungal number in dangke (n=20), isolation and identification of fungi in dangke, and observation of Lactobacillus plantarum DU15 (LAB) application in dangke which was contaminated with Candida sp. The study was designed using randomized completely design with factorial pattern of 4 x 2 x 4 with 5 replications. The result showed that the average number of fungi in 20 samples of dangke from Enrekang District were 5.2 x 106 cfu/g. The main isolated fungi strains were belonged to Candida sp. (95%), Saccharomyces sp. (50%), Geotrichum sp. (35%), Rodotorula sp. (10%), Microsporum sp. (40%), Cladosporium sp. (30%), Penicillium sp. (30%), Aspergillus sp. (20%), Fusarium sp. (5%). During the storage, pH, total lactic acid, and viable count of LAB increased significantly (p<0.05). LAB could reduce fungal growth significantly (p<0.05). The number of fungi decreased from 6.72 log cfu/g to 3.99 log cfu/g after 6 days of storage
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Judul: Karakterisasi Senyawa Antimikroba Dari Bakteri Lactobacillus Fermentum Dengan Media Whey Dangke
Abstrak: Dangke merupakan makanan khas Kabupaten Enrekang yang dibuat tanpa melalui proses fermentasi. Proses pembuatan dangke menghasilkan by product (hasil sampingan) berupa whey. Whey dangke dapat digunakan sebagai media pertumbuhan bakteri asam laktat karena mengandung nutrisi yang tinggi. Lactobacillus fermentum (L. fermentum) merupakan salah satu bakteri asam laktat yang mampu menghasilkan bakteriosin. Tujuan dari penelitian adalah untuk menganalisis potensi dangke sebagai media pertumbuhan L. fermentum asal dangke untuk menghasilkan bakteriosin. Strain L. fermentum asal dangke yang digunakan yaitu A323L, B323K, dan C113L. Metode penelitian meliputi beberapa tahap yaitu persiapan Bakteri Asam Laktat (BAL) dan bakteri patogen, pengujian nutrisi whey, pewarnaan Gram, pembuatan kurva pertumbuhan, dan purifikasi bakteriosin. Peubah yang diamati yaitu total BAL, nilai pH, total asam tertitrasi (TAT), aktivitas antimikroba bakteri L. fermentum, konsentrasi protein dan aktivitas antimikroba bakteriosin. Total BAL, Nilai TAT, nilai pH dianalisis menggunakan rancangan acak kelompok (RAK) pola faktorial, sedangkan aktivitas antimikroba bakteri, antimikroba bakteriosin dan konsentrasi protein dianalisis dengan menggunakan rancangan acak lengkap (RAL), data yang berbeda nyata dianalisis lebih lanjut dengan uji Duncan. Hasil penelitian menunjukkan bahwa fase logaritmik pada kurva pertumbuhan L. fermentum A323L yaitu pada waktu inkubasi 24-28 jam sedangkan B323K dan C113L pada waktu inkubasi 20-24 jam. Zona hambat yang dihasilkan oleh semua strain L. fermentum termasuk kategori lemah karena diameternya hanya kurang lebih 3 mm. Whey dangke dapat dimanfaatkan sebagai media pertumbuhan L. fermentum asal dangke karena BAL tersebut mampu mencapai fase pertumbuhan logaritmik. Namun kebutuhan nutrisi dalam media whey dangke belum tercukupi untuk menghasilkan bakteriosin. L. fermentum strain A323L, B323K, C113L asal dangke hanya mampu menghasilkan daya hambat kategori lemah (zona hambat kurang dari 3 mm) pada media whey dangke. Namun diantara ketiganya, strain yang terbaik adalah C113L.
Keyword: Lactobacillus fermentum, whey dangke, bakteriosin

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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