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: Rekayasa Bioproses Produksi Bioetanol dari Hidrolisat Pati Sagu (Metroxylon sp.) Menggunakan Saccharomyces Cerevisiae Var.ellipsoides Pada Kultivasi Nir-Sinambung dan Semi Sinambung:
Abstrak: Starch of sago is one of the sources of ethanol which is able to be produced by enzymatic hydrolysis and followed by cultivation process. It has high concentration of carbohydrate (80 %), so it can produce glucose highly with enzymatic hydrolysis process. The total amount of glucose has correlation with amount of ethanol, in cultivation process. The first step of research was to prepare substrate from sago starch which was hydrolysed enzymatically using α- amylase and amyloglucosidase (AMG) enzymes. Preliminary research was conducted to determine optimum concentration in which S.cerevisiae var.ellipsoides can live and produce the highest ethanol content. The concentrations being tested were 18, 24, 30 and 36 % (g/L) of total sugar. The main research consists of two systems: batch and fed-batch. Result shows that 24 % concentration (g/L) was find to be the optimum consentration for S.cerevisiae var.ellipsoides with ethanol production reaches up to 10,2 ± 0,000 % (w/v). One of the main research is using batch cultivation. The best result of highest ethanol concent was reached (10,77 ± 0,000 % w/v) when aeration was stopped after biomass condition has reached the maximum condition. The best result on fed-batch cultivation with the highest ethanol concentration (12,05 ± 0,00 % w/v) also was gained at the same treatment with feed concentration of glucose 16 % g/L. Based on calculation of cultivation kinetic parameters, it is shown that in batch cultivation the highest Yp/s, Yp/x (0,15; 0,47; 4,48) was gained on the third treatment that is aeration stopped at 30th hour. On fed-batch cultivation, the highest Yp/s and Yp/x value (0,51 and 5,05) is shown on treatment of which aeration is stopped after 30th hour and feed concentration of 16 % g/L.
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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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