Judul: Produksi dan Karakterisasi  Bakteriosin Asal Lactobacillus  plantarum  1A5 serta Aktivitas Antimikrobanya  terhadap Bakteri Patogen
Abstrak: The aims of this research were to study antimicrobial activity of bacteriocin produced by lactic acid bacteria Lactobacillus plantarum 1A5 in six different media (media with NaCl 1%, combination of NaCl 1% and YE 3%, and trypton 1% inducers that were conditioned on pH 5 dan pH 6, respectively). Characteristic of bacteriocin 1A5 determined by catalase and proteolytic enzymes with antagonistic assay against pathogenic bacterias (Staphylococcus aureus ATCC 25923, Salmonella typhimurium ATCC 14028 and enteropathogenic Escherichia coli K11) and determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericide Concentration (MBC)’s value against Staphylococcus aureus ATCC 25923. The result showed that the inhibitory activity was produced significantly by crude bacteriocin 1A5 from media with trypton 1% inducer and was conditioned at pH 6. Characterization of active compound from crude bacteriocin 1A5 could be classified as bacteriocin neither antimicrobial compounds such as hydrogen peroxide because it was stable to catalase treatment. The other characteristic of its bacteriocin was nature proteinaeous that showed loss it’s activity after trypsin treatment against Staphylococcus aureus ATCC 25923 and enteropathogenic Escherichia coli K11, neither Salmonella typhimurium ATCC 14028. Inhibition activity of crude bacteriocin 1A5 could explained with MIC and MBC’s value, especially against Staphylococcus aureus ATCC 25923. MIC’s and MBC’s value needed respectively 70% dan 80% concentration of crude bacteriocin.
Keyword: 

Judul: Production of Crude Bacteriocin Lactobacillus plantarum 2C12, 1A5, 1B1, 2B2 from Beef and Their Antimicrobial Activity Against Patogenic Bacteria
Abstrak: Bacteriocin is an antimicrobial peptides produced by lactic acid bacteria which can be a safe biopreservatif agent. The production of bacteriocin have to be done to replace the existence of synthetic preservatives which cause diseases and have been used to decrease the contamination of spoilage and pathogenic bacteria that can be found in many food material. The lactic acid bacteria which used in this research were the isolates of Lactobacillus plantarum 2C12, 1A5, 1B1 and 2B2, that have been isolated from local beef and deposited at Animal Science Faculty of Bogor Agriculture University. This research has been done from February to August 2011. The aims were to learn about the growth curves of L. plantarum 2C12, 1A5, 1B1 and 2B2, to identify the antimicrobial activity of crude bacteriocin from some different isolates lactic acid bacteria and their effects of to some indicator bacteria by diffusion well method agar. The observed variable in this research was the inhibitation zone around the well which refer to the antimicrobial activity from bacteriocin to indicator bacteria and it has been explained by Completely Randomized Design (CRD) with factorial arrangement 5x4. The results of this research showed that all isolates of L. plantarum (2C12, 1A5, 1B1 and 2B2) had some antimicrobial compounds which could decrase the indicator bacteria’s growth, such as Salmonella entritidis ser. Thypimurium ATCC 14028, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Bacillus cereus, dan Staphylococcus aureus ATCC 25923.
Keyword: 

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.
Keyword: