Judul: Bioethanol Production Yeast Wickerhamomyces anomalus Isolated from Tuak Bali.
Abstrak: Kebutuhan untuk mencapai sasaran peningkatan sumber energi alternatif melatarbelakangi penelitian terkait bioenergi, salah satunya bioetanol. Bioetanol merupakan senyawa organik hasil fermentasi substrat gula oleh mikrob. Isolasi dari produk Brem Tabuh didapatkan isolat yang terindentifikasi sebagai Wickerhamomyces anomalus. W. anomalus kode BT2, BT5, BT6 memiliki fenotipe toleran terhadap cekaman suhu, etanol, dan gula tinggi. Penelitian ini bertujuan untuk mengetahui kemampuan tiga strain W. anomalus dalam memanfaatkan berbagai substrat gula (glukosa, xilosa, maltosa, sukrosa, dekstrosa) pada media oxidative fermentative (OF), pengukuran efisiensi pemanfaatan gula, dan produksi etanol substrat terpilih dengan gas chromatography (GC). Pengujian menggunakan media OF menunjukkan ketiga strain menghasilkan reaksi positif disetiap gula uji, terbentuk gelembung gas dan perubahan warna media. Efisiensi pemanfaatan substrat terpilih (glukosa,xilosa,maltosa) setelah 48 jam inkubasi menunjukkan nilai efisiensi pemanfaatan substrat paling tinggi yaitu BT6 pada glukosa (61.02%), BT2 dan BT5 pada maltosa masing-masing 60.90% dan 58.44%. Pengukuran produksi etanol dengan GC menunjukkan ketiga strain mampu menghasilkan etanol yang lebih tinggi pada substrat glukosa dibandingkan substrat lainnya. BT6 dapat menghasilkan produksi etanol tertinggi (5.3g/l) pada substrat glukosa dibandingkan BT2 dan BT5. Namun strain tersebut hanya mampu menghasilkan 0.90g/l dan 0.60g/l pada substrat maltosa dan xilosa. Pengujian fermentasi lebih lanjut diperlukan untuk mengkonfirmasi kemampuan aktivitas strain BT6., The need to achieve the target of increasing demand of alternative energy sources is the background for the various studies related to bioenergy, including bioethanol. Bioethanol is an organic compound resulting from the fermentation of sugar substrates by microorganisms.A previous study has isolated three fermentation-stress tolerance yeast strains from traditional Balinese beverages, namely Wickerhamomyces anomalus BT2, BT5, BT6. These three strains are known to have a tolerant phenotype against temperature stress, ethanol, and high sugar concentrations. Our study indicates that these strains could utilize various sugar substrates (glucose, xylose, maltose, sucrose, dextrose) inoxidative fermentative media. The highest value of substrate utilization efficiency following 48 hours fermentation was shown by BT6 on glucose (61.02%), BT2 on xylose (55.44%) and maltose (60.9%). Measurement of ethanol production by GC showed that the three strains were able to produce higher ethanol on the glucose substrate than the other substrates. For instance, BT6 could produce the highest ethanol production (5.3g/l) amongst strains tested by using glucose as a substrate. Yet, the particular strains could only produce 0.90 g/l and 0.60g/l by using maltose and xylose, respectively. Further scale-up fermentation is necessary to confirm the activity of BT 6 strain.
Keyword: bioetanol, khamir, tuak bali, Wickerhamomyces anomalus, gas chromatography

Judul: Pembuatan Bioetanol Dari Sirup Glukosa Umbi Ganyong (Canna Edulis Kerr.) Menggunakan Khamir Schizosaccharomyces Pombe
Abstrak: Bioethanol is an ethanol produced by fermentation of biomass containing sugar/starch/cellulose such as sugar cane, cassava and sago. Ethanol is generally used in industry as an alcohol derivative material, ingredient of alcoholic liquors such as sake or gin, pharmaceutical and cosmetic material (Hambali et al., 2007). Ganyong is a crop that easily grows in all weather and soil type. Moreover, this crop doesn't need any complex requirement for its growth (Lingga et al., 1989). One hectare of land can produce 50 tons ganyong with approximately eight months seed time (Azahari, 2008). Based on the research conducted by Zuraida et al. (2002), ganyong had a fairly high level of starch content, which was between 31.3-38.9 %. The high level of starch content and productivity along with easiness of growth makes ganyong appreciated as a prospective material for bioethanol production. Schizosaccharomyces pombe is yeast with fermentative facultative characteristic and resistance to high sugar content. According to Barnett et al. (2000), Schizosaccharomyces pombe was one of osmophilic yeast, which had ability to grow on media with aw less than 0.85 equivalents to glucose content of 60 % w/w. This research consisted of preliminary research and main research. In main research stage 1, the comparison between extraction method with and without peeling process was performed. The performed analyses were included starch yield and starch content from the starch produced by both methods above. Preliminary research stage 2 was done to compare 4 types of glucose syrup with different sugar concentration. Those glucose syrups were made into carbon source in the substrate which then became the fermentation medium. Indicator of the best sugar concentration was its ability to grow the most yeast. Main analysis done in this research was the total of dry biomass in gram/L. Estimation of total biomass by measuring OD (Optical Density) value which would then be fitted into the standard curve of relation between OD and dry biomass. The result of preliminary research stage 1 was that the starch extraction method without peeling process produced higher yield than the method with peeling process. The yield of starch produced by the method without peeling process was 16.51 ± 3.88 % (w/w), while the yield produced by the method with peeling process was 7.05 ± 0.85 % (w/w). The starch content in both starch yields from each treatment was not significantly different. In preliminary research stage 2, the best sugar concentration to maximize growth of the microbe was 36 % (w/v), with μmax on the sixth hour. The aim of this research was to compare two agitation methods in fermentation to see its effect to the produced ethanol yield. In first method agitation was done until the end of fermentation (continued agitation). While in the second method agitation was only done until the time when μmax value was achieved (stopped agitation). The result of main research was that the continued agitation method produced more ethanol than the stopped agitation method. The ethanol content produced by continued agitation method was 19.26 ± 0.86 g/L, while the ethanol content produced by stopped agitation method was 13.79 ±
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Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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