Judul: Karakterisasi Xilanase Dari Bakteri Xilanolitik Asal Tanah Hutan Taman Nasional Bukit Duabelas Jambi Indonesia
Abstrak: Xilanase merupakan enzim ekstraseluler yang dapat dihasilkan oleh mikroba dan memiliki kemampuan mendegradasi xilan menjadi xilo-oligosakarida (XOS) dan xilosa. Xilanase banyak digunakan dalam bidang industri kertas dan produksi bioetanol. Aplikasi xilanase yang masih belum optimal salah satunya disebabkan oleh kurang tersedianya biakan mikroba unggul penghasil xilanase. Tujuan penelitian ini adalah mengetahui karakteristik xilanase dari isolat bakteri xilanolitik asal tanah Hutan Taman Nasional Bukit Duabelas Jambi, Indonesia. Isolat bakteri XJ20 merupakan isolat terpilih yang akan diuji lebih lanjut aktivitas dan karakteristik enzimnya. Aktivitas xilanase diukur dengan menggunakan metode 3.5-dinitrosalicylic acid (DNS). Xilanase yang dihasilkan oleh isolat XJ20 memiliki tiga puncak tertinggi aktivitas enzim yaitu pada jam ke-6 (0.015 U/mL), jam ke-14 (0.012 U/mL) dan jam ke-20 (0.007 U/mL). Puncak pertama dan puncak kedua mencapai aktivitas tertinggi pada suhu 70 oC namun puncak pertama optimum pada pH 4.0 dan puncak kedua pada pH 7.0. Pada pH 4.0 xilanase yang diinkubasi pada suhu ruang dan suhu 70 ˚C memiliki waktu paruh berturut-turut 9 jam dan 6 jam, sedangkan pada pH 7.0 4 jam dan 3 jam. Stabilitas enzim lebih baik pada pH 4.0 dan pada suhu ruang.
Keyword: aktivitas enzim, DNS, stabilitas enzim, xilanase, xilanolitik

Judul: Isolasi dan Pencirian Xilanase dari Bakteri Asal Tanah Hutan Taman Nasional Bukit Duabelas, Jambi, Indonesia
Abstrak: Xylanase is a xylan-degrading enzymes which are useful to improving the bioconversion of lignocellulosic biomass into useful products. Broad application of xylanase have not optimized due to the lack of superior microbes. The aim of this study is to isolate bacterial origin Bukit Duabelas National Park, Jambi and characterize its xylanase, including its pH optimum, temperature optimum, and stability. A total of 28 potential isolates have been isolated from Bukit Duabelas National Park soil, Jambi and three were successfully characterized its xilanase (isolates 10, 18, and 27). Isolate 10 reached the highest producing extracellular xylanase at 12th and 36th hours of culture incubation with optimum activity at pH 6, temperature 40 °C and 90 oC. Isolate 27 reached its highest producing extracellular xylanase at 12th and 30th hours of culture incubation. The optimum condition of xylanase isolate 27 occurred at pH 5, temperature 90 oC and 50 oC, while xylanase isolate 18 achieve its optimum production time at the 18th and 36th hours of incubation culture. Xylanase isolate 18 achieved its optimum condition at pH 5 and temperature 90 oC and has half-life time 1 hour 7 minutes.
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Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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