Judul: Optimasi Konsentrasi Xilosa dan Glukosa untuk Produksi Xilitol oleh Candida tropicalis
Abstrak: The objectives of this research were to determine the optimum time of incubation to harvest cell of Candida tropicalis and xylitol production, and optimum environtment condition to produce xylitol as well, including substrate and co-substrate concentration. In this research, were done optimization of xylose concentration 50-110 g/L and ratio of xylose and glucose between 6:1-6:4 (%). Fermentation was carried out at 300 C in 125 mL Erlenmeyer flask at 120 rpm for 48 hours. Xylitol concentration was measured by spectrophotometre method (D-sorbytol/D-xylitol kit). The research result showed that good xylose concentration to produce xylitol be in 30-70 g/L with highest product yield of xylose concentration be 30 g/L (Y product/substrate = 0.25 g/g) and the optimum ratio of xylose and glucose be 6:1 (%) which produces 4.81 g/L of xylitol, with addition of glucose was 12 g/L. The adding of glucose as co-substrate 12 – 48 g/L in the fermentation media could not increase xylitol production, but it has role to increase the cell biomass.
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Judul: Penambahan Glukosa sebagai Kosubstrat dan Pengaruhnya terhadap Produksi Xilitol oleh Candida guilliermondii
Abstrak: Xylitol is a five-carbon sugar alcohol and used commercially in various fields. Xylitol can be produced by solid-liquid extraction from fruits and vegetables, also chemical synthesis which is expensive and energy-intensive. Therefore, an alternative inexpensive production techniques is required, one of them is using microorganism. The purposes of this research were to determine the optimum incubation time for the growth of C. guilliermondii, and xylitol production, also to determine the best ratio variation of glucose:xylose. Fermentation was carried out at 300C with shaking speed 120 rpm. Ratio variation used in this research were (glucose:xylose) 1:25, 1:12, 1:5, 1:2.5. Xylitol concentration was measured with spectrophotometer based on D-sorbitol/Dxylose Kit. The results showed the log phase of the growth of C. guilliermondii at 12-36 hour, and the optimum incubation time to obtain the highest amount of xylitol at 72 hour. The best variation ratio of glucose:xylose is 1:5 with initial glucose concentration 9 g/L and xylose concentration 45 g/L. Xylitol obtained from ratio 1:5 was 2.85 g/L while xylitol obtained from control medium, which is the medium that contained only xylose 45 g/L was 0.57 g/L, thus the addition of glucose to fermentation medium can increase the production of xylitol.
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Judul: Identifikasi Kejadian Banjir Rob (Pasang) di DAS Sunter pada 9-13 Januari 2008.
Abstrak: Banjir Rob merupakan fenomena meluapnya air laut ke daratan, istilah tersebut pertama kali dikenal di daerah Semarang. Fenomena banjir Rob dipengaruhi oleh pasang surut air laut. Pasang surut sendiri dipengaruhi gravitasi bulan dan matahari, serta dipengaruhi pula posisi bulan dan matahari terhadap bumi. Banjir ini biasa terjadi pada saat pasang air laut yaitu bertepatan dengan kejadian bulan baru dan bulan purnama. Pada bulan Januari 2008, di wilayah utara Jakarta yang berbatasan dengan laut, fenomena banjir Rob (pasang) melanda kawasan tersebut. Fenomena ini mengakibatkan sejumlah kawasan di wilayah utara Jakarta terendam air laut, hal ini diperburuk dengan penurunan muka tanah Jakarta. Selain dilanda banjir pasang air laut, kawasan utara Jakarta sering dilanda banjir akibat luapan sungai-sungai yang bermuara di Jakarta, salah satu sungai yang menyumbang banjir Jakarta adalah sungai Sunter. Tutupan lahan di DAS Sunter yang sebagian besar berupa pemukiman makin meningkatkan limpasan permukaan ketika terjadi hujan. Tanggal 9-13 Januari 2008 di perairan Teluk Jakarta sedang terjadi pasang air laut karena bertepatan dengan bulan baru yang mengakibatkan terjadinya banjir Rob di beberapa wilayah di Jakarta Utara, termasuk DAS Sunter. Berdasarkan pemetaan banjir Rob di DAS Sunter pada tanggal 9-13 Januari 2008 diketahui bahwa daerah yang tergenang air laut yaitu Kalibaru dan Marunda dengan tinggi genangan 48-72 cm. Luas genangan maksimum terjadi pada tanggal 11 Januari 2008 yaitu sebesar 66.000 m2. Pada tanggal 9-13 Januari, DAS Sunter tidak ikut menyumbangkan limpasan permukaan yang dapat menyebabkan banjir karena nilai limpasan permukaan berkisar 0-3,03 mm. Sehingga kejadian banjir pada tanggal 9-13 Januari 2008 di DAS Sunter hanya berasal dari pasang air laut. Kata Kunci : Banjir Rob, Pasang-Surut, Limpasan Permukaan, DAS Sunter.
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