Judul: Isolasi dan Identifikasi Mikrob Tanah Pendegradasi Selulosa dan Pektin dari Rhizosfer Aquilaria malaccensis
Abstrak: Gaharu (agarwood) is one of non-timber forest product that has been used for thousand years by ancestors in religious rituals, as perfume, incense, fragrance, even for medicines. Gaharu can be found commonly from trees of genus Aquilaria. Scientists indicated various hypothesis to understand agarwood formation in the tree, one of them is pathological hypothesis. In pathological hypothesis, agarwood formation is caused by microbial infection inside plant tissue host. The presence of pathogen attack will make the host to produce phytoalexins as self defence. Thus, it is estimated that agarwood formation conducted by accumulation of phytoalexins in damage plant tissues. This research aims to explore soil microbes in rhizosphere of Aquilaria malaccensis which have ability to degrade cellulose and pectin. Screening was conducted to observe cellulase and pectinase activities. Isolates were screened in selective media, namely CMC (carboxymethyl cellulose), CPAF (citrus pectin agar for fungi) and CPAB (citrus pectin agar for bacteria). Cellulase and pectinase activity was specifically shown by clear zone around the cultures after flooding treatment with stain solution. Identification was conducted for isolate that showed the highest solubilizing index after screening section. Soil parameters that play role in microbial living in nature had been measured, such as pH, soil moisture content, bulk density, Ca, Mg, Fe, Cu, Mn, Zn, C-organic, total Nitrogen, and available Phosphate. In this research, 26 isolates of fungi and 29 isolates of bacteria were isolated. It was found that seven isolates of fungi and six isolates of bacteria showed positive result with clear zone around the cultures. The results of identification showed soil microbes with the highest cellulose and pectin solubilizing index are Bacillus brevis for bacteria and genus Helicoma for fungi.
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Judul: Peranan Zat Ekstraktif Dalam Pembentukan Gaharu Pada Aquilaria crassna Pierre ex Lecomte dan Aquilaria microcarpa Baill
Abstrak: This research is aimed at investigating the anti fungal activity (AFA), the correlation of gaharu tree’s phenolics in relation with the susceptibility of the trees to Fusarium bulbigenum attack in the formation of agarwood, and to observe total phenolics content and tree’s chemicals of Aquilaria crassna and Aquilaria microcarpa pre-inoculation, the reology of tree’s chemical and microorganism change along inoculation time. There were variations of anti fungal activity among trees, and the highest is at tree no. 10 that AFA was in the middle class (39,77%), but entirely agarwood trees exhibited a low anti fungal activity at lab scale. Further fractionation and bioassay showed that the most active component are likely in the ethyl acetate fraction that exhibited strong anti fungal activity at 4% concentration. Trees as many as 20 of A. microcarpa at Carita and 10 of A. crassna at Darmaga were inoculated with isolate of F.bulbigenum in spiral pattern around the stem. Prior to inoculation, strips were taken from the stem for total phenolics content and chemicals analyzing. The result revealed that total phenolics content and infection area exhibited a negative correlation, which means the higher the phenolics content, the smaller the infection area. The preinoculation chemicals analysis showed that tree with smaller infection area had larger type of compounds and higher concentration of phenolics than tree with wider one. Some chemicals that at certain plants acted as defense system, according to some references, were found at higher concentration in the gaharu trees with smaller infection or they were not even traced in other tree. The reology analysis revealed that the largest types of compounds were noticed at three day’s old inoculation. Agarwood constituents and other aromatic compounds were detected since three days after inoculation which is indicated the agarwood formation was taken place. Meanwhile, the microbiology analysis showed there was no microbes change in the inoculation sites along 6 month inoculation time, but some small insects, such as ants and bugs, were found at the area.
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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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