Judul: Penapisan Bakteri Penghasil Enzim Selulase dari Bakteri Laut yang Berasosiasi dengan Spons
Abstrak: Bakteri laut yang berasosiasi dengan spons dapat dimanfaatkan sebagai sumber enzim baru, terutama selulase yang dapat dimanfaatkan untuk produksi bioetanol dari selulosa. Penelitian ini bertujuan mengisolasi, menapis, dan mengidentifikasi secara molekular bakteri selulolitik yang berasosiasi dengan spons. Sebanyak 38 isolat bakteri berhasil diisolasi dari spons Aaptos sp., Euryspongia sp., dan Haliclona sp. dengan spread plate method. Sebanyak 14 isolat (37%) dari 38 isolat bakteri yang berasosiasi dengan spons menunjukkan aktivitas selulolitik secara kualitatif pada medium carboxy methyl cellulose (CMC) dengan indeks selulolitik berkisar antara 0,31 hingga 1,63. Aktivitas selulolitik tiga isolat yang menunjukkan indeks selulolitik tertinggi yaitu Y.5.10, Y.5.11, dan Y.40.6 diuji secara kuantitatif. Isolat Y.5.10, Y.5.11, dan Y.40.6 menunjukkan aktivitas selulolitik berturut-turut 0,0053 U/mL; 0,0083 U/mL; dan 0,0124 U/mL. Aktivitas spesifik tertinggi ditunjukkan oleh isolat Y.40.6 dengan nilai 0,3391 U/mg. Hasil identifikasi berdasarkan sekuens gen 16S rRNA menunjukkan bahwa isolat Y.5.10, Y.5.11, dan Y.40.6 secara berturut-turut memiliki kemiripan yang tinggi (kemiripan ≥ 99%) dengan Bacillus sp., B. subtilis, dan B. cereus.
Keyword: cellulase, sponge-associated bacteria, 16S rRNA

Judul: Karakterisasi Molekuler Bakteri Laut Penghasil Senyawa Bioaktif yang Berasosiasi dengan Spons dan Toksisitas Ekstraknya
Abstrak: Mikroorganisme laut diketahui memiliki hubungan simbiosis dengan spons. Mikroorganisme simbion dapat mensintesis berbagai senyawa bioaktif dalam bentuk metabolit sekunder yang berperan dalam suksesi ekologi simbion inangnya. Penelitian ini bertujuan melakukan uji penapisan terhadap Candida albican dan Candida tropicalis, mengidentifikasi bakteri berdasarkan gen penyandi 16S rRNA, mendeteksi gen penyandi enzim PKS (poliketida sintase) dan NRPS (nonribosomal peptida sintetase), serta menguji toksisitas senyawa bioaktif dengan menggunakan larva Artemia salina. Hasil uji penapisan menunjukkan bahwa enam isolat dengan kode CAL 36, PTR 8, PTR 21, PTR 40, PTR 41, dan PTR 47 dapat menghambat pertumbuhan C. tropicalis, lima diantaranya dapat menghambat pertumbuhan C. albican. Ketujuh isolat merupakan bakteri penghasil senyawa bioaktif yang ditunjukkan dengan teramplifikasinya gen penyandi enzim NRPS, sedangkan dua diantaranya memiliki gen penyandi enzim PKS. Setelah dilakukan identifikasi berdasarkan 16S rRNA dihasilkan bahwa bakteri yang berasosiasi dengan spons Petrosia sp. memiliki persen kemiripan sebesar 100% untuk kode isolat PTR 41 dan 99% untuk kode isolat PTR 8, PTR 21, PTR 40, dan PTR 47 dengan bakteri Pseudomonas putida KT2440 strain KT2440, sedangkan bakteri yang berasosiasi dengan spons Callyspongia sp. dengan kode isolat CAL 36 dan CAL 42 memiliki persen kemiripan sebesar 100% dengan bakteri Pseudoalteromonas flavipulchra strain NCIMB 2033. Uji toksisitas ekstrak menggunakan metode BSLT menghasilkan nilai LC50 tertinggi sebesar 40.38 μg/mL pada PTR 8 dan terendah sebesar 376.70 μg/mL pada CAL 42.
Keyword: Bakteri asosiasi spons, ekstrak senyawa bioaktif, NRPS (nonribosomal peptida sintetase), PKS (poliketida sintase), toksisitas

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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