Judul: Produksi Xilitol dari Hidrolisat Limbah Tandan Kosong Sawit oleh Candida tropicalis.
Abstrak: Limbah padat terbesar yang dihasilkan dari perkebunan kelapa sawit salah satunya adalah tandan kosong kelapa sawit (TKKS). Limbah tersebut hingga saat ini dimanfaatkan sebagai pupuk organik namun pemanfaatan tersebut belum maksimal. Limbah TKKS dengan komponen utama hemiselulosa, selulosa, dan lignin dapat dihidrolisis menjadi xilosa dan dikonversi menjadi produk xilitol yang memiliki nilai jual tinggi. Xilitol merupakan gula alkohol yang memiliki manfaat untuk mencegah kerusakan gigi, memiliki nilai kalori dan nilai glikemik yang rendah sehingga aman bagi penderita diabetes. Penelitian ini bertujuan untuk memproduksi xilitol dari limbah TKKS dengan pemberian arabinosa sebagai kosubstrat pada sel Candida tropicalis. Xilosa dihidrolisis secara kimiawi menggunakan asam dan rendemen yang dihasilkan diukur dengan metode DNS, nilai rendemen xilosa tertinggi yaitu 4.93%. Xilitol yang dihasilkan diukur dengan ELISA Reader menggunakan kit D-sorbitol Colorimetric Assay pada panjang gelombang 540 nm dan waktu inkubasi selama 30 menit. Kadar xilitol tertinggi yang dihasilkan pada sampel TKKS sebesar 13.559%. Penambahan ko-substrat arabinosa tertinggi diperoleh pada arabinosa 5% di waktu fermentasi 8 jam.
Keyword: Arabinosa, C. tropicalis, tandan kosong kelapa sawit, xilitol

Judul: Optimasi Konsentrasi Arabinosa sebagai Ko-substrat untuk Produksi Xilitol oleh Sel Amobil Candida tropicalis
Abstrak: This research was carried out to investigate xylitol production by Candida tropicalis immobilized cells under two sets condition, which were addition of arabinose as a co-substrate and its fermented on sugar mixed medium. Ratio xylose to arabinose was used at the range 6:1-6:3% (xylose 30 g/L and arabinose 5-15 g/L). Sugar mixed medium variation which used in this research were xylose and glucose; xylose and arabinose; and also xylose, glucose, and arabinose, respectively. Candida tropicalis cells entrapped in Ca-alginate and incubated in batch fermentation on 100 rpm rotary shaker at 30˚C for 96 hours. Xylitol produced by cells were measured using spectrophotometer and by D-sorbitol/Dxylitol enzymatic assays. The results revealed that addition of arabinose at the range 6:1-6:3% could increased xylitol production (3.11-5.90 g/L). The highest volumetric rate of xylitol production (0.06 g/L h) and yield product (0.20 g xylitol produced /g xylose consumed) were achieved at ratio 6:3%. Contrary with glucose in fermentation medium could decreased xylitol production of 20% compared with control medium. This negative effect of glucose was annulled by adding arabinose in sugar mixed medium containing xylose, glucose, and arabinose can reached xylitol production for 4.2 g/L.
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Judul: Exchange Market Pressure and Central Bank Intervention for Three ASEAN Countries
Abstrak: Two of the exchange rate systems which are adopted by many countries are the floating and the fixed exchange rate system. Both the exchange rate systems have different characteristics. Countries that implement fixed exchange rates system tend to set their domestic currency exchange rate at a certain point. On the contrary, countries which implement floating exchange rate system tend to let their domestic currency exchange rate to move flexibly and thus their value will always change according to the demand and supply of the currency in the foreign exchange market. Countries which implement floating exchange rate system are facing the risk of fluctuation in the exchange rate of their domestic currency against foreign currencies. The currency exchange rate fluctuation may be caused by economic problems such as a financial crisis. A country can also be potentially affected by other countries’ earlier financial crisis. This effect could potentially happen if these countries are in the same region, such as ASEAN. The 1997 ASEAN economic crisis was an example of a country’s financial crisis could affect other countries. At that time, some countries such as Indonesia, Malaysia and Thailand had to change their currency exchange rate system from the fixed exchange rate system to the floating exchange rate system due to the high costs which has to be incurred if they were to enforce the fixed exchange rate system. During 2002 until 2012, the domestic exchange rate of Indonesia, Malaysia and Thailand against the U.S. dollar had tended to fluctuate. If the domestic currency exchange rate fluctuated excessively then the central bank would intervene to stabilize the exchange rate in the foreign exchange market. The pressure on domestic currency exchange rate pressures has forced the central bank to intervene. The amount of those pressures can be analyzed by calculating the Exchange Market Pressure (EMP) index. Apart from that, the time when interventions are done by the central bank can be known based on EMP by calculating the Exchange Market Intervention (EMI) index. The purposes of this study were to determine the level of international pressure on the currency exchange market and monetary authorities intervene in three ASEAN countries, as well as to determine the effect of the monetary authorities intervene on the exchange rate of the domestic currency against the U.S. dollar in those three ASEAN countries. Based on the EMP index calculation results which are obtained during 2002 to 2012 period, the exchange rate of Indonesia, Malaysia and Thailand’s domestic currency had always fluctuated and the results of the EMP index indicated that each country were under diverse level of currency exchange rate appreciation and depreciation pressures. Thailand was the country with the highest currency exchange rate pressure compared to Indonesia and Malaysia. The results on the intervention index calculation showed that Indonesia, Malaysia and Thailand have intervention index between zero and one and more than one. We can also see from the intervention index that Indonesia and Thailand implement the controlled floating currency exchange rate instead of the freely floating one. Based on the calculation of the currency exchange rate by comparing
Keyword: exchange rate, exchange market pressure, intervention