Judul: Isolasi dan Karakterisasi Bakteri Penghasil Biosurfaktan
Abstrak: Aktivitas petrogenik dan pirogenik di wilayah pesisir DKI Jakarta, khususnya sungai Cilincing mengakibatkan tercemarnya wilayah perairan oleh senyawa hidrokarbon. Bakteri penghasil biosurfaktan dapat dijadikan sebagai alternatif penangan pencemaran tersebut karena bersifat lebih ramah lingkungan dan toksisitasnya rendah jika dibandingkan dengan surfaktan sintetis. Penelitian ini bertujuan untuk mengisolasi dan mengarakterisasi bakteri penghasil biosurfaktan dari sampel tanah Sungai Cilincing. Isolasi bakteri dilakukan dengan menggunakan Mineral Salt Media (MSM) dengan menggunakan sumber karbon berupa solar 2%. Karakterisasi dilakukan dengan menguji aktivitas hemolisis, drop-collapse test, dan oil-spreading test. Sebanyak 19 isolat berhasil diisolasi dari sampel tanah Sungai Cilincing yang dibedakan berdasarkan ciri morfologinya. Berdasarkan hasil pewarnaan Gram, 15 isolat tergolong Gram positif dan 4 isolat tergolong Gram negatif. Dari 19 isolat yang mampu tumbuh pada media MSM +2% solar, sebanyak 9 isolat memberi hasil positif pada lebih dari satu uji dan diduga mampu memproduksi biosurfaktan, namun hanya satu isolat yang memberikan hasil negatif pada pengujian aktivitas hemolisis, yaitu isolat STC234. Isolat tersebut memiliki nilai indeks emulsifikasi sebesar 44,665±0,001%., The petrogenic and pyrogenic activities in the coastal areas of DKI Jakarta, especially the Cilincing River, have resulted in the contamination of water areas by hydrocarbon compounds. Biosurfactant-producing bacteria can be used as an alternative solution to handle the pollution because it is more environmental friendly and has low toxicity compared to synthetic surfactants. This study aims to isolate and characterize biosurfactant-producing bacteria from Cilincing River soil samples. Bacterial isolation was carried out using Mineral Salt Media (MSM) using 2% diesel as a carbon source. Characterization was done by testing the activity of hemolysis, drop-collapse test, and oil-spreading test. Total of 19 isolates were isolated from Cilincing River soil samples which were differentiated based on their morphological characteristics. Based on the results of Gram staining, 15 isolates were classified as Gram positive and 4 isolates classified as Gram negative. From 19 isolates that were able to grow on MSM +2% diesel media, 9 isolates gave positive results in more than one test and assumed to be able to produce biosurfactants, but only one isolate gave negative results on hemolytic activity tests, namely isolate STC234. The isolate had an emulsification index value of 44.665±0.001%.
Keyword: bioremediation, biosurfactant, Cilincing River, emulsification, hydrocarbon

Judul: lsolasi, ldentifikasi Bakteri Penghasil Biosurfaktan dari Reservoir Minyak Bumi dan Karakterisasi Biosurfaktan yang Dihasilkannya untuk Enhanced Oil Recovery
Abstrak: Biosurfaktan merupakan zat aktif permukaan yang disintesis oleh mikroorganisme. Zat ini mempunyai kemampuan menurunkan tegangan permukaan dan tegangan antarmuka dalam larutan maupun campuran hidrokarbon, yang berpotensi untuk meningkatkan pengurasan minyak bumi. Dalam penelitian ini telah dilakukan isolasi dan identifikasi bakteri penghasil biosurfaktan dari reservoir minyak bumi dan telah dilakukan karakterisasi biosurfaktan yang dihasilkan. Hasil penelitian ini diharapkan dapat diterapkan dalam teknologi pengurasan minyak bumi dengan menumbuhkan bakteri tersebut ke dalam reservoir. Dari tahap isolasi telah berhasil diisolasi 82 isolat bakteri, 10 isolat mampu menghasilkan biosurfaktan. Dua di antaranya yaitu isolat P106O15 dan P106T4 telah diidentifikasi berdasarkan Microbact 12E, BioMerieux API 20E dan sekuen gen 16S RNA serta dilakukan analisis kinerja isolat P106O15 dan P106T 4 dan karakterisasi biosurfaktan yang dihasilkan meliputi: 1) kinetika pertumbuhan dan pembentukan biosurfaktan; 2) kemampuan menurunkan tegangan antarmuka; 3) analisis jenis biosurfaktan dan komposisi senyawa penyusunnya. ldentifikasi isolat P106O15 adalah Providencia rettgeri, menghasilkan biosurfaktan mulai awal pertumbuhan hingga fase kematian sel, nilai tegangan antarmuka terendah sebesar 0,00 mN/m pada jam inkubasi ke 80, biosurfaktan yang dihasilkan merupakan jenis lipopeptida. ldentifikasi isolat P106T4 adalah Bacillus subtilis, menghasilkan biosurfaktan mulai awal pertumbuhan hingga fase kematian sel, nilai tegangan antarmuka terendah sebesar 0,02 mN/m pada jam inkubasi ke 80, biosurfaktan yang dihasilkan merupakan jenis lipopeptida.
Keyword: identifikasi bakteri, reservoir, minyak bumi, biosurfakta, Enhanced Oil Recovery

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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