Judul: Memanfaatkan ragi probiotik multifungsi dari dadih, produk fermentasi tradisional dari Sumatera Barat,Indonesia
Abstrak: Fermented buffalo milk, commonly called Dadih, contains potential probiotic yeast cells. Probiotic yeast has garnered increasing attention in basic and clinical science over the past 20 years. This research aimed to isolate, characterize, and determine the biodiversity of potential probiotic yeasts obtained from Dadih. Isolation of probiotic yeast was done using Yeast Extract, Peptone, and Dextrose (YPD) media, followed by the identification of yeast using Sequence-Related Amplified Polymorphism (SRAP). Colonies relatedness was determined using the Numerical Taxonomy and Multivariate Analysis System (NTSYS). Two yeast isolates were further identified using Polymerase Chain Reaction (PCR) targeting the 18S rRNA gene. The probiotic characterization was done by determining pH resistance, bile salt resistance, proteolytic, lipolytic test, and hemolytic tests. Secondary metabolites were determined by conducting antioxidant, antidiabetic, antiinflammation, and antimicrobial tests. Interaction between secondary metabolites signals was determined by molecular docking using AutoDock software. Whole genome sequencing on Pichia kudriavzevii using Oxford Nanopore Technologies and genome annotation was performed using the Rapid Annotation using the Subsystem Technology (RAST) server. Fifty-five colonies were isolated, and their relatedness showed a minimum cutoff at a similarity level of 89% in the dendrogram. Two isolates, GBT 30 and GBT 37 were identified as Pichia occidentalis and Pichia kudriavzevii, respectively, based on the 18S rRNA sequence. Acid pH tolerance results showed both isolates survived at an acidic pH starting at pH 2 to pH 6. A bile salt resistance test showed that both isolates were able to show significant cell viability in 0.3 and 0.5% bile salt concentrations. Both isolates produced secondary metabolites, with GBT 30 showing good antimicrobial and antiinflammation properties than GBT 37. Whole-genome sequencing of P. kudriavzevii revealed a genome size of 10 906 850 bp, comprising five chromosomes with an average GC content of 38.26%, and secondary metabolites located on contig 7., Susu kerbau fermentasi yang biasa disebut Dadih mengandung sel ragi probiotik yang potensial. Ragi probiotik telah mendapatkan perhatian yang semakin besar dalam ilmu dasar dan klinis selama 20 tahun terakhir. Penelitian ini bertujuan untuk mengisolasi, mengkarakterisasi, dan mengetahui keanekaragaman hayati khamir probiotik potensial yang diperoleh dari Dadih. Isolasi ragi probiotik dilakukan menggunakan media Yeast Extract, Peptone, dan Dextrose (YPD), dilanjutkan dengan identifikasi ragi menggunakan Sequence-Related Aplified Polymorphism (SRAP). Keterkaitan koloni ditentukan dengan menggunakan Numerical Taxonomy and Multivariate Analysis System (NTSYS). Dua isolat khamir diidentifikasi lebih lanjut menggunakan Polymerase Chain Reaction (PCR) dengan sasaran gen 18S rRNA. Karakterisasi probiotik dilakukan dengan menentukan ketahanan pH, ketahanan garam empedu, proteolitik, uji lipolitik, dan uji hemolitik. Metabolit sekunder ditentukan dengan melakukan uji antioksidan, antidiabetes, antiinflamasi, dan antimikroba. Interaksi antara sinyal metabolit sekunder ditentukan dengan molekuler docking menggunakan perangkat lunak AutoDock. Pengurutan seluruh genom pada Pichia kudriavzevii menggunakan Oxford Nanopore Technologies dan anotasi genom dilakukan menggunakan Rapid Annotation menggunakan server Subsystem Technology (RAST). Lima puluh lima koloni diisolasi, dan keterkaitannya menunjukkan batas minimum pada tingkat kemiripan 89% pada dendrogram. Dua isolat, GBT 30 dan GBT 37 masing-masing diidentifikasi sebagai Pichia occidentalis dan Pichia kudriavzevii, berdasarkan urutan 18S rRNA. Hasil toleransi pH asam menunjukkan kedua isolat mampu bertahan pada pH asam mulai pH 2 hingga pH 6. Uji ketahanan terhadap
Keyword: probiotic, Whole Genome Sequencing, Pichia kudriavzevii, Pichia occidentalis, dadih, fermentation

Judul: Identifikasi Dan Karakterisasi Substrat Antimikroba Dari Bakteri Asam Laktat Kandidat Probiotik Yang Diisolasi Dari Dadiah Dan Yogurt
Abstrak: Probiotic has been defined as living microorganism that, when administered in adequate of amounts, confered a health benefit on the host. One of criterias that must be fulfilled by lactic acid bacteria as a probiotic is its ability to produce antimicrobial compounds that were capable inhibit toward pathogenic bacterias. Lactic acid bacteria (LAB) can be isolated from fermented milk. Maheswari (2008) isolated Lactobacillus plantarum D-01 and Lactococcus lactis D-01 from buffalo milk fermented called ‘dadiah’ traditionally produced by people from West and North Sumatra, and also isolated Bifidobacterium longum Y-01 and Lactobacillus acidophilus Y-01 from yogurt. Their potential as probiotic culture was interested to determine especially for their ability to produce antimicrobial substrate that inhibit pathogenic bacterias. Identification of nature and characterization of antimicrobial substrate produce by LABs tested for its stability at different pH and storage’s temperature, and proteolitic’s enzyme by agar well diffusion method. The culture supernatants inhibited toward Salmonella Ser. Typhimurium ATCC 14028, Escherichia coli ATCC 25922, and Staphylococcus aureus ATCC 25923. The supernatants showed an antimicrobial activity against phatogenic bacteria and identified as organic acid and hydrogen peroxide. The existance of proteinaceous antibacterial compound, which referred as bacteriosin, was proved through proteolityc activity on supernatants that resulted in decrease of zone inhibition diameters. Characterization determined that proteinaceous antibacterial compound was stable at room storage temperature within five days and at cold storage temperature within two weeks. Meanwhile, proteinaceous antibacterial compounds were not heat stable and not stable when adjusted in different pH, especially when adjusted in pH above 5. Four LABs tested could be considered as probiotic bacterias because all of LABs produced antimicrobial compounds consist of organic acid, hydrogen peroxide and bacteriosin that inhibited pathogenic indicator bacterias.
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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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