Judul: Eksplorasi bakteri selulolitik penghasil polihidroksialkanoat(PHA)
Abstrak: Mikroorganisme kini telah banyak dimanfaatkan dalam bidang industri. Polihidroksialkanoat (PHA) merupakan cadangan makanan dan karbon yang diakumulasi bakteri di dalam selnya dan bisa digunakan sebagai bahan baku plastik biodegradabel. Penelitian ini bertujuan untuk mendapatkan bakteri selulolitik yang teridentifikasi mampu menghasilkan PHA dari berbagai sampel di alam yang diambil dari beberapa lokasi di Pulau Jawa dan Kalimantan Tengah. Penelitian ini dilakukan pada bulan Februari-November 2003 di Laboratorium Mikrobiologi dan Bioteknologi Lingkungan, Pusat Penelitian Lingkungan Hidup, Institut Pertanian Bogor. Berdasarkan hasil penelitian, didapatkan sebanyak 15 isolat bakteri pendegradasi selulosa yang mampu menghasilkan PHA di dalam selnya. Indikasi adanya zona bening disekitar koloni sel setelah dilakukan pewarnaan iodium menunjukkan bahwa isolat tersebut mampu mendegradasi selulosa. Uji kemampuan akumulasi PHA 15 isolat tersebut dilakukan dengan pewarnaan Sudan Black B, xylene, dan safranin, dengan indikasi adanya granul yang berwarna kehitaman atau kebiruan di dalam sel bakteri sedangkan sitoplasma berwarna merah ketika diamati di bawah mikroskop dengan perbesaran 1000x. Sepuluh dari 15 isolat bakteri selulolitik yang dapat menghasilkan PHA, diidentifikasi lebih lanjut menggunakan Microbact 12E (Australia). Sepuluh isolat tersebut adalah: Pseudomonas sp (ICBB 7122), Alcaligenes sp (ICBB 7123), Micrococcus sp (ICBB 7124), Microbacterium lacticum (ICBB 7125 dan ICBB 7126), Citrobacter freundi (ICBB 7127), Corynebacterium sp (ICBB 7128), Bacillus brevis (ICBB 7129), Shigella sp (ICBB 7130), Bacillus pumilus (ICBB 7131).
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Judul: Isolation and Screening of PHA Producing Halotolerant Actinobacteria from High Salinity Environment
Abstrak: Plastik konvensional menjadi masalah lingkungan yang genting dihadapi oleh umat manusia akibat dari persistensinya di lingkungan hidup. Hal ini menyebabkan pencarian alternatif terhadap plastik tersebut menjadi sebuah urgensi. Salah satu alternatifnya yaitu polihidroksialkanoat (PHA), biopolimer termoplastik yang dapat disintesis oleh beragam jenis bakteri sebagai cadangan energi termasuk aktinobakteri yang merupakan salah satu filum terbesar di kelompok bakteri. Biaya produksi yang tinggi dari polihidroksialkanoat mengarahkan eksplorasi terhadap mikroorganisme halotoleran (ekstremofil) sebagai sumber produk. Oleh karena itu, penelitian ini bertujuan mengisolasi aktinobakteri halotoleran penghasil polihidroksialkanoat (PHA). Isolat-isolat yang digunakan diisolasi dari berbagai lingkungan bersalinitas tinggi di Indonesia. Setelah dimurnikan isolat-isolat yang didapatkan kemudian ditumbuhkan pada media induksi ISP9-I dan ditapis dengan menggunakan zat warna Sudan Black B dan Nile Red. Polimer yang diekstraksi dari isolat yang positif kemudian dikuantifikasi dan divalidasi menggunakan analisis gravimetrik dan uji asam krotonat. Analisis gravimetrik menunjukkan produktivitas PHA oleh isolat HVB mencapai 78,426%, sedangkan uji asam krotonat memvalidasi dan menunjukkan hasil 1,982% poli(3-hidroksibutirat) (P3HB) yang mengindikasikan tipe heteropolimer., Conventional plastics have become an urgent environmental problem for human due to their persistence in the environment. This issue has led to the exploration of alternatives. One of them is polyhydroxyalkanoates (PHA), a thermoplastic biopolymer synthesized by various bacteria as an internal energy storage compound, including actinobacteria, one of the largest Gram-positive bacteria phylum. However, the high production cost of PHA is a significant factor contributing to its non-competitiveness in the market. This has led to the exploration of halotolerant bacteria (extremophiles) as a potential producer of PHA. Therefore, this study aims to isolate indigenous PHA producer halotolerant actinobacteria. The actinobacteria used in this study were isolated from various high-salinity environments in Indonesia. After purification, isolates were cultured in ISP9-I broth media and screened by using Sudan Black B and Nile Red dyes. The extracted polymer from both positive screenings was then quantified and validated using gravimetric analysis and crotonic acid assay. The analysis showed PHA productivity by HVB can reach up to 78,426% of the dry cell weight, whereas the crotonic acid assay showed 1,982% of the extract is poly(3-hydroxybutyrate) (P3HB), indicating that extracted the polymer is a heteropolymer.
Keyword: extremophiles, Gram positive, PHA, plastic, P3HB

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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