Judul: Identifikasi Molekuler Bakteri Pengurai Kitin Serangga dan Karakterisasi Enzim Kitinasenya
Abstrak: Rhizobacteria have beneficial effects for plant growth as phytostymulator, biofertilizer, and biocontrol agent. Our previous study showed that rhizobacteria of I.5, I.21, and II.14 isolates produced chitinases. The enzymes could degrade chitin of leaf miner (Aphis gossypi) and white fly (Bemisia tabaci). This research was conducted to identify the bacteria based on 16S r-RNA gene sequences and to characterize protein of chitinase from selected rhizobacteria. PCR amplification of 16S rRNA gene yielded DNA fragments of 1300 bp for each isolate. Based on sequences of the 16S rRNA gene, I.5 isolate was similar to Bacillus sp. with similarity percentage of 88% and I.21 and II.14 isolates were similar to B. cereus with similarity percentage of 93% and 91% respectively. Zymogram analyses showed that molecular weight of chitinase from I.21 isolate was 145 kDA and 168 kDa. However, no protein bands were showed in zymogram analyses of I.5 and II.14 isolates. Three chitinolytic bacteria have an opportunity to be used as natural biocontrols and bioinsecticides.
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Judul: Karakterisasi kitinase hasil pemurnian parsial dari isolat bakteri tanah asal Cianjur
Abstrak: Kitinase (EC 3.2.1.14) merupakan enzim yang mampu menghidrolisis kitin yang terdapat dalam eksoskeleton serangga, bakteri, dan jamur, serta enzim ini berpotensi sebagai agen biokontrol. Tujuan penelitian ini adalah memurnikan dan mengkarakterisasi kitinase dari isolat terpilih, serta mengukur kemampuan penghambatan terhadap jamur Colletotrichum sp. oleh bakteri kitinolitik. Aktivitas kitinase ditentukan dengan metode Spindler dan kadar proteinnya ditentukan dengan metode Bradford. Produksi kitinase isolat rizobakteri menunjukkan aktivitas spesifik kitinase tertinggi sebesar 0.0489 U/mg pada isolat C5C dengan pemurnian amonium sulfat 70% serta dapat meningkatkan kemurnian 13.97 kali dibandingkan ekstrak kasar dan fraksi lainnya. Karakterisasi kitinase asal isolat C5C menunjukkan bahwa enzim aktif pada suhu 55 °C, pH 7, waktu inkubasi optimum 120 menit, serta enzim ini memiliki nilai Km sebesar 1.300x 103 mg/L dan Vmaks sebesar 0.0294 mg L -1 detik-1 . Aktivitas antifungi isolat bakteri kitinolitik C5C dapat menghambat pertumbuhan jamur Colletotrichum sp. secara in vitro.
Keyword: Biocontrol, Chitin, Chitinase, Colletotrichum sp., Rhizobacteria, Insect, Bacteria, Fungi, Biocontrol agent, Chitinolitic bacteria, In vitro

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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