Judul: Pemurnian dan Karakterisasi Protease Ekstraseluler Isolat Bakteri Termofilik GP-04
Abstrak: A gram positive, rod-shaped, and aerobic thermophilic bacterium, designated as GP-04, was isolated from Gunung Pancar hot spring, near Bogor, West Java. Based on approximately 400 bases both 5 frames regions and 3 frames ends DNA sequences of 16s-rRNA gene, the isolate is determined to be closely related ± 90%) to Bacillus caldovelox. The isolate, produced significant amount of extracellular protease when grown in a modified Thermophilic Bacillus medium pH 7,O at 6s°C for 16 h in a batch mode fermentation. Crude protease was purified using 30% ammonium sulphate precipitation and column chromatography using Sephadex G-25 followed by DEAESephadex A-50.
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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: The Effects of Variance of Interest rate to Variance of Annuity Future Values
Abstrak: Time value of money is a concept that refers to the difference of the value of money due to time difference. The value of money for present time would not be the same as the value of money in the future. The value of money for present time is called as Present Value (PV) of the money and the value of money for future time is called Future Value (FV) of the money. Determination the value of money, for present and future time, depends on the time and rate of return. The value of money is determined by several factors such as inflation, fluctuation of interest rates, and government policy in securities and taxation. Due to fluctuation of the value of money we need a FV formulation, it is useful for knowing whether an investment can be profitable or not, and this information is useful also in budget analysis. Annuity is defined as a series of payments made for a specific period. The payment, fixed or varied, can be made at the beginning or at the end of the period. Annuity paid at the beginning of the period is called annuity-due and annuity paid at the end of the period is called immediate annuity-certain. The accumulated value of the annuity after few years later is called as a final value or a future value. Burnecki et al. (2003) have discussed about the FV of a fixed-rate annuity in which payments are made according to the arithmetic or geometric series. They have also examined FV for annuities in which payments are made according to arithmetic or geometric series with random rates of interest. This paper examines FV for annuity-due in which payments are made according to arithmetic or geometric series with interest rates as a random variable, which is normal distribution ,  . Future value formula is expressed in recursive form. FV for annuity-due which payments are made according to the arithmetic or geometric series with random rates of interest is calculated by theoretical way and simulation way. The random rates of interest is denoted as k k i  i  , where k i an independent random variable; i is a constant and k  is a random variable which has normal distribution ,  . By using the determined parameters, a sequence of random rates of interest are generated for theoretical calculation. Meanwhile for the simulation, the random rates of interest is generated 1000 times for the simulation. The generated data give mean value, variance, and standard deviation. Moreover, error of mean value, variance, and standard deviation from the theoretical and simulation results are calculated. Error calculation uses Symmetric Mean Absolute Percentage Error (SMAPE). The smaller the value of SMAPE is the more accurate the simulation. The interest rate variances are varied from 0.000036 to 0.0001 to study the relationship between variance of rates of interest and variance of future value. The theoretical and simulation results show that when the variance of random rates of interest increases, then the variance of FV increases linearly. FV of the annuity-due in
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