Judul: Produksi bioetanol dari empulur sagu menggunakan enzim dan khamir dari isolat lokal
Abstrak: Starch and fiber from Sago palm can be used for making bioethanol. Starch are accumulate in the pith core of sago palm steam. The pith was pretreated with conventional heating (autoclaving) or microwave. After pretreatment, the sago pith was hydrolysed using α-amylase at 95 oC. The saccharification of sago pith was conducted using consortia of three enzymes (amyloglucosidase, cellulase and xylanase) at 60 o C. Hydrolysis of sago pith was done with these commercial starch degradating enzymes and self-prepared enzymes from local isolates of cellulolytic and xylanolytic bacteria. Yeast used at the fermentation process was isolated from rotten fruits. Selection of yeast was based on their ability to consume mixed substrates of xylose and glucose; and the ethanol production. After 72 hours of fermentation the ethanol production was analyzed using Gas Chromatography. Ethanol produced from conventional heating was greater than microwave heating by using yeast isolate MP (8.11%).
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Judul: Pengaruh pemanasan gelombang mikro dua tahap pada hidrolisis asam empulur sagu untuk produksi bioetanol
Abstrak: Sago is a genus of palm that can be utilized to produce fermentable sugars as substrate for bioethanol. Sago pith is a heterogeneous substrate consists of starch and fiber. Acid hydrolysis by microwave heating radiation can break down starch and fibers together in a very short time, so it is considered to be very efficient. The use of microwave energy (as power level) and variation of heating time can produce fermentable sugar with certain characteristics. This study included the preparation of sago pith flour, pith composition analysis including proximate components, starch, and fiber components, the process of acid hydrolysis (0.3 M and 0.5 M sulphuric acid) with two steps microwave heating (power level 30% with time variation 1 minute, 2 minutes and 3 minutes the next step followed by power level 70% for 3 minutes), and characterization of fermentable sugar. As comparison, conventional treatment carried out using the autoclave on 121oC for 15 minutes. The highest sugar (105.7 g/l) contents of fermentable sugar is produced from microwave heating with power level 30% for 2 minutes followed by the power level 70% for 3 minutes. This hydrolyzate then used as substrate fermentation for Issatchenkia orientalis with different acidity (pH 3, 4 and 5), but highest ethanol produced from substrate with pH 5. Ethanol produced is still low (2.8 g/l) compared with autoclave treatment (14.5 g/). Not all sugar were consumed and it is proved that Issatchenkia orientalis only consumed glucose for growth and ethanol production.
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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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