Judul: Isolasi dan karakterisasi dekstransukrase dari isolat  bakteri batang tebu (PSIB 92001)
Abstrak: Dekstransukrase (EC 2.4.1.5) adalh enzim dari kelompok glukosiltransferase yang mengkatalisis perpindahan gugus alpha-D-glukopyranosil dari sukrosa ke dekstran dengan membebaskan fruktosa. Enzim ini diperjualbelikan dengan harga yang sangat mahal. Dekstransukrase dan dekstran belum dapat diproduksi di Indonesia, walaupun pengaruh adanya dekstran telah lama mengganggu produksi gula Indonesia. Tujuan penelitian ini adalah untuk mengisolasi dekstransukrase dari media fermentasi yang telah diinokulasi bakteri PSIB 92001 dan menentukan karakterisasi enzim.
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Judul: Karakteristik Isolat Bakteri Penghasil Dekstran dari Batang Tebu (Saccharum officinarum L.).
Abstrak: Dekstran merupakan polisakarida yang terdiri atas α(1→6)–ikatan glukan yang disintesis oleh enzim dekstransukrase. Dekstransukrase memiliki dua fungsi yaitu pertama, menghidrolisis sukrosa dan mengikat bagian glukosil, setelah itu membangun rantai dekstran dengan mekanisme penyisipan. Dekstran dihasilkan oleh mikroba yang biasanya banyak ditemukan pada tebu yang terlambat giling atau penanganan pascapanen yang kurang baik. Tujuan dari penelitian ini yaitu untuk mengisolasi dan mengkarakterisasi bakteri penghasil dekstran dari batang tebu. Penelitian ini dilakukan dengan cara mengisolasi bakteri penghasil dekstran dari tanaman tebu. Bagian batang yang digunakan yaitu tebu batang bawah (TBB) dan tebu batang tengah (TBT). Sampel dipotong dan dimasukkan ke dalam media selektif yang mengandung 10% sukrosa, kemudian diinkubasi selama 24 jam pada suhu 25oC dan diamati perubahan viskositas pada kultur sebagai indikasi pembentukan dekstran. Isolat terpilih kemudian diidentifikasi berdasarkan pewarnaan Gram dan morfologi koloni. Isolat yang memiliki kemampuan pembentukan dekstran tertinggi selanjutnya dikarakterisasi untuk melihat pengaruh waktu, suhu, pH dan konsentrasi sukrosa terhadap pembentukan dekstran. Identifikasi isolat terpilih secara molekuler dilakukan dengan sekuen gen 16s rRNA. Sebanyak 6 isolat terpilih (TBT 2, TBT 3.1, TBT 3.2, TBB 1.1, TBB 1.2 dan TBB 5) berdasarkan adanya pembentukan senyawa dekstran pada permukaan media yang mengandung sukrosa. Isolat TBT 3.2 memiliki nilai viskositas teritinggi sebesar 1.48 cP dan berat rendemen dekstran tertinggi yaitu 7.87 g/L. Adanya aktivitas dekstransukrase (29.41 mU/mL) dan aktivitas spesifik (0.46 U/mg)) dari isolat TBT 3.2 menunjukan adanya proses pembentukan dekstran oleh enzim tersebut. Kondisi pertumbuhan isolat TBT 3.2 dalam menghasilkan dekstran berdasarkan hasil karakterisasi yaitu pada media dengan pH 7, suhu 30 oC dan konsentrasi sukrosa 20%. Identifikasi isolat berdasarkan gen 16s rRNA menunjukkan bahwa isolat TBT 3.2 berkerabat dekat dengan Paenibacillus polymyxa dengan tingkat kemiripan 99%.
Keyword: dekstran, dekstransukrase, Paenibacillus polymyxa, tebu

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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