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: Selection for Saccharomyces cerevisiae Isolates Resistant to Furfural Inhibitors for Bioethanol Production
Abstrak: Saccharomyces cerevisiae dapat digunakan sebagai penghasil bioetanol karena dapat memproduksi etanol dalam jumlah besar, mempunyai toleransi tinggi terhadap etanol, dan resisten terhadap inhibitor. Tujuan penelitian ini adalah mendapatkan isolat S. cerevisiae yang tahan terhadap inhibitor furfural. S. cerevisiae yang diisolasi dari fermentasi tape singkong, peyeum, dan tape ketan dianalisis kadar etanolnya menggunakan KCKT. Hasil analisis KCKT menunjukkan tiga isolat dengan kadar etanol tertinggi adalah TKH (BGR) 10.5.1.1, TKH (BGR) 10.5.2.3, dan TKPK 10.5.1.A. Ketiga isolat tersebut kemudian diuji ketahanannya terhadap inhibitor furfural 0 mM, 30 mM, dan 60 mM. Hasil pengujian menunjukkan bahwa hanya sampel dari isolat TKH (BGR) 10.5.1.1 yang tahan terhadap inhibitor pada konsentrasi 60 mM. Sampel dari isolat TKH (BGR) 10.5.1.1 kemudian diuji pertumbuhannya menggunakan sumber karbon glukosa 30 g/L, xilosa 30 g/L, dan glukosa 30 g/L + xilosa 50 g/L dan menunjukkan hasil pertumbuhan yang baik pada sumber karbon glukosa 30 g/L dan glukosa 30 g/L + xilosa 50 g/L., S. cerevisiae can be used as an ethanol producer because can produce a high amount of ethanol, high ethanol tolerance, and inhibitor-resistant capability. This study aims to obtain S. cerevisiae that can resist furfural. S. cerevisiae isolated from fermented cassava, peyeum, and fermented sticky rice were analyzed the ethanol by using KCKT. The results showed that three isolates with the highest ethanol are TKH (BGR) 10.5.1.1, TKH (BGR) 10.5.2.3, dan TKPK 10.5.1.A. Then, the best three isolates were tested for furfural inhibitor with concentration 0 mM, 30 mM and 60 mM. The results indicated that an isolate of TKH (BGR) 10.5.1.1 was the best candidate for furfural tolerance. It was performed the growth in 30 g/L glucose, 30 g/L xylose and a combination of 30 g/L glucose with 50 g/L xylose. The result showed that TKH (BGR) 10.5.1.1 can grow well in glucose 30 g/L and in a combination of glucose 30g/L and xylose 50 g/L.
Keyword: bioetanol, furfural, KCKT, Saccharomyces cerevisiae

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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