Judul: Physiological Characterization and Molecular Identification of Methanotrophic Bacteria isolated from Ricefields in Bogor and Sukabumi.
Abstrak: Methane (CH4) is one of the main greenhouse gasses that could absorb infra-red radiation so it contribute to global warming. Methanotrophs are bacteria that are able to grow using methane as their only source of carbon and energy. They play a major role in the reduction of the release of methane into the atmosphere from environments. Methanotrophic bacteria isolated from Ricefields in Bogor and Sukabumi (BGM 1, BGM 2, BGM 3, BGM 9, and SKM 14) had a high methane oxidation. Activity physiologycal assay using API 20 NE and molecular identification using 16S rRNA gene sequence analysis were conducted in this research. Five isolates showed a positive reaction of physiological assays for gelatine, β-galactosidase enzyme, glucose assimilation, mannitol assimilation, N-asetil-glukosamin assimilation, maltose assimilation, and malic acid assimilation. BGM 1 and BGM 3 16S rRNA sequence showed that they had similarity to Methylocystis rosea into 74% and 70% respectively, while BGM 2 and BGM 9 had similarity to Methylococcus capsulatu into 83% and 85% respectively, and SKM 14 had 65% similarity with Methylobacter sp. Phylogenetic tree showed that BGM 1 and BGM 3 isolates were in the same group with Methylocystis rosea strain SV97T, Methylobacterium extorquens, and Methylosinus trichosporium, nevertheless they were very close related to Methylocystis rosea strain SV97T. BGM 2, BGM 9, and SKM 14 isolates were in the same group with Methylococcus capsulatus strain texas, Methylomicrobium buryatense, and Methylobacter sp. nevertheless BGM 2 and BGM 9 isolates were very close related to Methylococcus capsulatus strain texas. While SKM 14 was very close related with Methylobacter sp.
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Judul: Methane oxidation activity of methanotrophic bacteria from ricefields under different consentration of oxygen
Abstrak: Methane-oxidizing bacteria (methanotrophs) have ability to oxidize methane to carbon dioxide via methanol, formaldehyde, and format in aerobic condition. Methanotrophic bacteria are normally abundant where methane is present. In aerobic environment, methanotrophic bacteria oxidize methane to provide carbon and energy for their growth. Methanotrophic bacteria have an unique enzyme known as methane mono oxygenase (MMO) catalizing reaction of CH4 and O2 to methanol. Three selected isolates from rice fields in Bogor and Sukabumi were tested the growth and methane oxidation activity under different concentration of oxygen (02) using Nitrat Medium Salts (NMS) medium. Methane oxidation rate ofBGM 9 isolate at 0%,10%, 20% and 50% air saturation was 129182.06 mol/day, 138185.16 mol/day, 137484.32 mol/day, 167015,88 mol/day respectively. In contl:ast, high rates of Methane oxidation were performed by BGM 2 and SKM 14 isolates at air saturation of 10% and 20%. However the activity was decreased at 50% air saturation.
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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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