Judul: Screening of Probiotic Bacteria for Biocuntrol of Vibriosis in Tiger Shrimp Larvae: Construction of Molecular Marker and Adherence Assay.
Abstrak: Probiotic bacteria for biocontrol of vibriosis were isolated from tiger shrimp larvae and hatchery environment. Almost all probiotic isolates could inhibit the growth of pathogenic Vibrio harveyi. SKT-b isolate from SkeIetonema was very effective in inhibiting V, harveyi and significantly reduced larval mortality in pathogen challenge assays. These prospective probiotic bacteria, at concentration 10'-10~ CFU/ml, did not show pathogenicity to shrimp larvae. SKT-b was Gram negative, short rod shape, exhibited yellow colonies an TCBS and swarming an SWC-agar media, motile, utilized glucose and sucrose but not lactose; produced extmcellular protease ancl amylase, but did not produce &itinasen Partial sequencing of 16s-rRMA gene showed that SKT-b was similar to Vib* algindyticus. To analyse mechanism of tiisease suppression by SKT-b, especially on their competition for adhesion sites, we constructed recombinant V. herveyi carrying gfp gene as a rnokufar marker. V. harvayi carrying gfp don& in a broad-host range plasmid (pWGO1) resulted in green-fluarescent colonies and cells due to the production of GFP, Growth cuwe analysis and pathogenicity assays showed that the recombinant V. Harveyi exhibited similar growth profiles as the wild type parental strain and did not show alteration in their pathogenicity. However, under nun selective long-term experiments without antibiotic pressure, pWGO? was not staMy maintained in any V. harveyi strains used in this study. Therefore we canstructed a mini Tn5 and TnIO transpuson containing gfp gene to be inserted into V. hatveyfs genamic DNA to yield stable transcanjugants. Tn5 transposition in V. harvejli strains did nut yield any transcanjugants, although we could obtain relatively trigti (10~t)r ansmjugans employing Tn10. One uf Tn 10 derived isolate of V, harvoyi G3 ((33-Tnf Ogfp) showed gfp expression and was further employed for adherence assay. Fluorescent G3-TnPOgfp cells could be obwwed inside the digestive tract of shrimp lanrae and fts population with SKT-b treatment was lower than without pmbiatic, demonstrating possible cornpetitiun for adherence sites or nutrition between V. harvsyi and SKY-b. ltrtroduction of SWb into shrimp tame through SKT-Mnriched Ademr'a resulted in higher growth rate than the mtro
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Judul: Selection of probiotic bacteria for controlling vibriosis on tiger grouper (Epinephelus fuscoguttatus)
Abstrak: Vibriosis is a bacterial disease affecting farmed fish including grouper. Disease control usually uses antibiotic but can lead to ecological inbalance and antibioticresistant pathogens. The use of probiotic bacteria is one of the methods in aquaculture that is used to control infectious diseases. The aims of this study were to obtain and isolate pathogenic Vibrio in the tiger grouper, to select bacterial probiotic candidates in controlling vibriosis, to evaluate efficacy of probiotic bacterial administration in controlling vibriosis in tiger grouper fry, and to evaluate probiotic bacterial candidates in enhancing immune responses. The first step was isolation and characterization of pathogenic bacteria as causative agent of vibriosis on grouper. Secondly, selection of probiotic candidate bacteria was conducted from the coral reef and tiger grouper fish farming environment including isolation of probiotic candidates, selection of probiotic candidates using inhibition test, co-culture method, and pathogenicity test of selected probiotic candidates. The third and fourth steps were administration of probiotic candidate bacteria on tiger grouper fry and juvenile, respectively, on feed for 28 days, and challenge test was performed at day-29. The result indicated that V6 isolate was the most pathogenic among isolates. Moreover, from 124 isolates, based on selection of probiotic candidates bacteria using inhibition zone and co-culture methods, there were found four potential isolates namely K7, K8, K21, T41, and K15, K55, K68, T36, respectively. Four isolates, namely K7, K8, T36 and T41, had high survival rate of fish in pathogenicity test. Furthermore, T36 isolate may decrease pathogenic Vibrio population, increase immune response, survival rate and growth rate of tiger grouper. According to gene sequencing analysis using 16S-rRNA, V6 dan T36 were Vibrio parahaemolyticus and Bacillus cereus, respectively.
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Judul: Perbandingan Metode Monte Carlo dan Kuasi Monte Carlo dalam Penentuan Harga Opsi Eropa
Abstrak: Opsi adalah suatu kontrak antara dua pihak di mana pemegang opsi mempunyai hak untuk membeli atau menjual suatu aset tertentu dengan harga yang telah ditentukan, pada atau sebelum waktu jatuh tempo. Opsi sebagai produk derivatif dapat mengurangi dampak risiko dalam berinvestasi dengan melakukan hedging (lindung nilai). Opsi Eropa merupakan opsi yang hanya dapat dieksekusi pada saat jatuh tempo. Karya ilmiah ini membahas penentuan harga opsi Eropa dengan menggunakan metode Monte Carlo dan Kuasi Monte Carlo dan hasilnya dibandingkan dengan harga opsi standar yang telah dihitung dengan menggunakan model Black Scholes. Berdasarkan hasil penghitungan, metode Kuasi Monte Carlo lebih cepat konvergen dengan galat relatif yang lebih kecil dibandingkan dengan metode Monte Carlo dalam penentuan harga opsi Eropa. Dengan demikian, dapat disimpulkan bahwa metode Kuasi Monte Carlo merupakan metode yang lebih baik dibandingkan metode Monte Carlo dalam penentuan harga opsi Eropa.
Keyword: opsi Eropa, Black Scholes, Monte Carlo, Kuasi Monte Carlo