Judul: Determination of Bacterial Communities in Processing Plants of the Blue Swimming Crab Meat Pasteurized Industry with Metagenomic Techniques
Abstrak: Komunitas bakteri yang ada di lingkungan produksi berpengaruh terhadap kualitas dan kemanan produk. Program sanitasi dilakukan untuk mengendalikan bakteri pada ruang produksi. Pengujian bakteri secara konvensional hanya mengidentifikasi bakteri yang dapat dikultur, sehingga pengujian metagenomik menjadi solusi untuk mengidentifikasi seluruh bakteri. Penelitian ini bertujuan mengidentifikasi komunitas bakteri saat proses produksi dan setelah prosedur sanitasi. Prosedur penelitian meliputi pengambilan sampel, inkubasi bakteri, perhitungan bakteri, isolasi DNA bakteri, sekuensing DNA, dan analisis bioinformatika. Sampel selama proses produksi memiliki kelimpahan absolut dan yang lebih tinggi dibanding sampel setelah prosedur sanitasi dilakukan dengan penurunan kelimpahan absolut sebesar 5,26%. Genus yang mendominasi yaitu Bacillales dengan kelimpahan relatif saat proses produksi (16,7%) dan mengalami penurunan setelah program sanitasi (4,7%). Pengujian molekuler dapat melengkapi pengujian konvensional dengan mengidentifikasi seluruh bakteri, The bacterial community in the production environment affects the quality and safety of the product. Sanitation programs can control the bacterial community in the production environment. Conventional method can only identify bacteria that can be cultured, so metagenomic method is a solution to identify all bacteria. This study aimed to identify bacterial communities during the production and after sanitation procedures. The research procedures included sample collection, bacterial incubation, bacterial counting, bacterial DNA isolation, DNA sequencing, and bioinformatics analysis. Samples during production had higher absolute abundance than after sanitation with decreased 5.26%. Genus that dominates is Bacillales with a relative abundance during the production (16.7%) and decreased after the sanitation (4.7%). Molecular method can complement conventional method by identifying all bacterial.
Keyword: lingkungan produksi, metagenomik, NGS, prosedur sanitasi, rajungan kaleng

Judul: Identification of Bacterial Communities in Eastern Little Tuna (Euthynnus affinis) from Traditional and Modern Market Locations with Metagenomic Analysis
Abstrak: Penanganan pasca panen dengan penerapan rantai dingin dan higiene yang baik merupakan tahapan penting untuk dapat menjaga kualitas ikan dan keamanan pangan. Perbedaan tingkat higiene yang diterapkan pada pasar tradisional dan modern akan mempengaruhi komunitas bakteri pada ikan tongkol. Penelitian ini bertujuan mengisolasi DNA bakteri dan mengidentifikasi komunitas bakteri dengan analisis metagenomik. Tahapan penelitian terdiri dari pengumpulan sampel, inkubasi bakteri, isolasi DNA bakteri dengan kit komersial, permurnian isolat DNA, Next Generation Sequencing dengan target gen 16S rRNA wilayah variabel V3-V4, dan analisis data dengan program bioinformatika. Kelimpahan sekuens bakteri pada ikan tongkol yang berasal dari pasar tradisional sebanyak 42.829 sekuen sedangkan dari pasar modern sebanyak 30.989 sekuen. Filum bakteri yang mendominasi pada kedua sampel tersebut yaitu Fusobakteriota, Bakteroidota, dan Patescibakteria. Komunitas bakteri pada ikan tongkol pasar tradisional memiliki kelimpahan relatif tertinggi pada genus Myroides (42,3%) sedangkan dari pasar modern pada genus Cetobacterium (80,2%)., Post-harvest handling, which includes the use of cold chain and proper hygiene, is a critical in maintaining fish quality and food safety. The bacterial community in eastern little tuna will be affected by differences in the level of hygiene used in traditional and modern markets. This study aims to isolate bacterial DNA and identify bacterial communities by metagenomic analysis. The research stages consisted of sample collection, bacterial incubation, isolation of bacterial DNA with commercial kits, purification of DNA isolates, NGS with the target gene for 16S rRNA V3-V4 variable region, and data analysis using bioinformatics programs. The sequence abundance of bacteria in eastern little tuna from traditional markets was 42.829 sequences while those from modern markets were 30.989 sequences. Fusobakteriota, Bacteroidota, and Patescibakteria were the most predominant bacterial phyla in both samples. Traditional market eastern little tuna had the highest relative abundance in the genus Myroides (42,3%), while the modern had the highest relative abundance in the genus Cetobacterium (80,2%).
Keyword: 16S rRNA, Next Generation Sequencing, Bacterial communities, Eastern Little Tuna, Hygiene

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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