Judul: Karakteristik Ketahanan Bakteri Asam Laktat Indigenous Dadiah Sebagai Kandidat Probiotik Pada Kondisi Saluran Pencernaan in vitro
Abstrak: Probiotic bacteria defined as living microorganisms which will confer health benefit to the host when administered in adequate amounts. The aims of this research were to study the potential of Lactobacillus plantarum D-01, Lactococcus lactis D-01, Bifidobacterium longum Y-01, and Lactobacillus acidophilius Y-01 as probiotic bacteria through its ability to survive in gastrointestinal conditions (acid conditions of stomach and the presence of bile salts in the small intestine), its resistance to antibiotics, and its antimicrobial properties against pathogen bacterias. This study initiated with assays of four tested Lactic Acid Bacterias for its ability to grow and survive in acid conditions and the presence of bile salts or antibiotics, also its antagonistic activities against indicator strains of pathogen bacterias (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Salmonella Thypimurium ATCC 14028). Result showed the ability of L. plantarum D-01, L. lactis D-01, B. longum Y-01 and L. acidophilus Y-01 to grow in acid conditions and tolerance at the presence of bile salts and antibiotics (t-test). Research found that difference species LABs tested influenced diameter of the inhibition zone against pathogen indicator bacterias (P<0.01). L. acidophilus Y-01 had the largest inhibition zone against S. Thypimurium ATCC 14028 and E. coli ATCC 25922, while B. longum Y-01 was able to produce the largest inhibition zone against S. aureus ATCC 25923 (P<0,05). Based on the characterization of four species LAB, it could be concluded that L. plantarum D-01, L. lactis D-01, B. longum Y-01, and L. acidophilius Y-01 can be used as probiotic.
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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: Pricing of Lookback Options with Floating Strike Price Using The Monte Carlo Method
Abstrak: Opsi lookback adalah opsi yang payoff-nya bergantung pada harga saham terbesar atau harga saham terkecil yang dicapai selama masa berlaku opsi. Opsi lookback dikatakan dengan floating strike price jika nilai dari strike price sebesar harga saham pada saat jatuh tempo. Nilai hampiran opsi lookback ditentukan dengan metode Monte Carlo, sedangkan nilai eksak didapat dari nilai simulasi terbesar yang mampu dihitung oleh komputer. Berdasarkan hasil penghitungan, nilai galat relatif yang dihasilkan semakin kecil dengan semakin bertambah banyaknya simulasi yang dilakukan, sehingga metode Monte Carlo untuk menghitung harga opsi lookback dengan floating strike price konvergen ke nilai eksaknya., Lookback option is an option whose payoff depends on the maximum or minimum of the asset price reached during the option period. The lookback option is said to be a floating strike price if the value of the strike price is equal to the stock price at maturity. The value of the lookback option is determined by the Monte Carlo method, while the exact value is obtained from the largest simulation value that the computer can compute. Based on the calculation results, the resulting relative error value get smaller with the increasing number of simulations performed. Therefore, the Monte Carlo method to calculate the price of the lookback option with the floating strike price converges to the exact value.
Keyword: lookback option, floating strike price, Monte Carlo method, convergent