Judul: Karakterisasi enzim hidrolase bakteri dari mata air soda Parbubu, Tapanuli Utara
Abstrak: North Tapanuli has a soda fountain as a source of potential biotic diversity of Indonesia, one of which is the hydrolytic bacteria. The purpose of this study was to isolate bacteria from the soda fountain and test Parbubu hidrolasenya enzyme activities, ie lipase, protease, and cellulase enzyme hidrolase and characterize the best in certain conditions of temperature and pH. Isolation of bacteria from the soda fountain Parbubu using pour plate method produced 23 isolates of bacteria. Test semikualitatif hidrolase enzyme using hydrolytic enzymes in media index showed that the bacterial isolates P9 has the highest lipase activity. Harvest time P9 bacterial lipase based on the growth curve and enzyme production curves, ie on the seventh hour of incubation. Lipase activity determined with titrimetric method shows that the fraction of the enzyme by precipitation (60-80)% of ammonium sulfate has the highest activity, that is equal to 3.5245 U / mL or 5992 times the activity of crude extract. Lipase enzyme has optimum activity at pH 7, at 5.9593 U / mL and at a temperature of 90 º C with the activity of 4.9019 U / mL.
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Judul: Isolasi dan Optimasi Protease Bakteri Termofilik dari Sumber Air Panas Tangkuban Perahu Bandung
Abstrak: Protease is an enzyme widely used in food industry. Thermophilic bacteria produce protease that can withstand high temperature. The research was aimed to isolate thermophilic bacteria and characterize protease of isolates with highest proteolytic index. Isolation was carried out on 33 isolates from three hot springs. Isolation was done by using pour plate method. Protease activity was measured by Bergmeyer, and protease characterization was conducted at pH 6-10 and temperature of 50oC- 90oC. The results showed that two isolates from Sipaholon hot spring, eleven isolates from Tangkuban Perahu hot spring, and two isolates from Ciseeng hot spring established clear areas around their colonies. T8 isolate derived from Tangkuban Perahu hot spring showed the highest proteolytic index of 33.5 and was used for further testing. The highest proteolytic activity of T8 isolate was obtained at 21th hour amounted to 3.8375 x 10-3 U/mL. Protease activity increased in ammonium sulphate 60% fraction, which was 7.7257 x 10-3 U/mL. Statistical analysis showed that pH and temperature affected protease activity. The optimum protease activity was obtained at pH 8 Clark & Lubs buffer and temperature of 60oC.
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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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