Judul: Efektivitas fiksasi N2 dan oksidasi metan kultur campuran bakteri metanotrof asal sawah
Abstrak: Sebagian besar emisi CH4 di lahan sawah yang tergenang diproduksi oleh bakteri metanogen dan sebanyak 80 % dari CH4 tersebut dioksidasi oleh bakteri metanotrof. Selain kemampuan mengoksidasi metan, metanotrof juga memiliki kemampuan memfiksasi nitrogen. Empat isolat metanotrof dengan kemampuan fiksasi nitrogen (BGM 1, BGM 3, BGM 5, dan BGM 9) masing-masing dikombinasikan dengan isolat metanotrof yang memiliki aktivitas oksidasi metan tinggi (SKM 14) untuk mendapatkan formulasi metanotrof yang tinggi aktivitas fiksasi nitrogen dan oksidasi metan-nya. Kemampuan fiksasi nitrogen diukur dari kadar amonium yang diakumulasikan dalam medium pertumbuhannya dan aktivitas reduksi asetilen (ARA). Akumulasi amonium tertinggi dicapai oleh kultur BGM 1 untuk kultur tunggal (1,86 μM amonium), dan kultur BGM 3/BGM 9 untuk kultur kombinasi (4,905 μM amonium). Aktivitas nitrogenase tertinggi ditunjukkan oleh kombinasi BGM 1/SKM 14 (11,27 μmol/ml kultur/hari), sedangkan aktivitas oksidasi metan tertinggi dicapai oleh kultur campuran BGM 5/BGM 9 (18,20 ppm/ml kultur/hari).
Keyword: Metan, Bakteri metanotrof, ARA, Fiksasi nitrogen, Oksidasi metan, Bogor Agricultural University, Institut Pertanian Bogor, IPB

Judul: Aktivitas fiksasi nitrogen dan oksidasi metan kultur campuran bakteri metanotrof pada lumpur sawah
Abstrak: Metanotroph bacteria are methane oxidizing bacteria. Besides, type II and type X of methanotrophic bacteria were also able to fix nitrogen using nitrogenase enzyme. This reasearch was conducted to test the activity of nitrogen fixation and methane oxidation of five isolates of methanotropic bacteria i.e. BGM 1, BGM 3, BGM 5, BGM 9, and SKM 14 which combined with one another. Seven combinations (SKM 14/BGM 1; SKM 14/BGM 3; SKM 14/BGM 5; SKM 14/BGM 9; BGM 9/BGM 1; BGM 9/BGM 3; BGM 9/BGM 5) were cultured and inoculated into NMS medium mixed with slurry of mud, then the activity of methane oxidation, nitrogen fixation and nitrogenase enzyme activity was tested. The highest accumulation of ammonium in the mud sterile treatment (35.489 μM) was higher than that of in non-sterile mud treatment (26.617 μM). Formulation 6 (BGM 9/BGM 3) in sterile mud treatment and formulation 4 (SKM 14/BGM 9) in non-sterile mud treatment has the highest nitrogenase enzyme activity, it was 5,16 mmol/h/ml culture and 75,85 mmol/h/ml culture respectively. Formulation 1 (SKM 14/BGM 1) and formulation 2 (SKM 14/BGM3) had the higest activity of methane oxidation in sterile and non sterile mud treatment i.e. 17428 and 16759 ppm /ml culture /day respectively.
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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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