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: Pengaruh Pemanasan Microwave Terhadap Sifat Penerimaan Enzim Amilolitik dan Holoselulolitik Untuk Produksi Fermentable Sugar dari Empulur Sagu (Metroxylon sagu)
Abstrak: Sago (Metroxylon sagu) has been one of the important raw materials for the production of useful substances. Because contains more than 80% carbohydrates, which is consists of 55.86% starch and 14.52% lignocellulosic material, the utilization of sago pith is essential for the fermentable sugar production in terms bioenergy production. In other hand, using the sago pith might prevent the waste of the resources. Lignin is one of the main components in lignocellulosic materials in sago pith. Its existence influence the sago pith structural rigidity by holding and stiffening the fibres together so decreasing the enzymatic suspectibility of sago pith. The use of microwave radiation is a promising approach to pretreatment that utilizes thermal and non-thermal effects generated by microwaves in aqueous environments. This study have shown that the microwave heating caused the process of swelling and gelatinization of starch granules and also could enhance lignin degradation itself. Thus could be very efficient in destroying the starch and lignin crystalline arrangement, obtaining a soft gel, and destroying cellulose-hemicellulose structure. On the other hand, if the energy that given to the slurry of sago pith more than it needed then it would build resistant characteristic of sago pith and increasing enzymes concentration wouldn’t enhance yield of reducing sugars. Pretreatment were evaluated based on yields of total sugars, reducing sugars, polymerization degree, equivalent dextrose, filtrate volumes, weight of residue, and filtrate purity from enzymatic hydrolysis of the pretreated biomass. The experimental results in this study can be used in existing simultant process of bioethanol production by using Pichia stipitis and Saaccharomyces elippsoides. The highest ethanol content was given by technical glucose and fermented by Pichia stipitis, prove the pretreatment could not efficiently degradated biomass due to the lignin content was too high. Thus, the lignin content is one of the matter in efficiently pretreatment in order to get the highest yield of reducing sugars.
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Judul: Teknik penentuan posisi bintang berdasarkan pelat foto overlapping
Abstrak: Bintang adalah salah satu objek langit yang menarik untuk diamati. Untuk itu, pengetahuan tentang posisi bintang sangat diperlukan. Posisi bintang di langit dapat dihitung melalui foto bintang. Fotografi astronomi atau astrometri merupakan ilmu yang mempelajari metode untuk menentukan posisi bendabenda langit seperti bintang berdasarkan pelat foto (Kamp, 1967). Sebuah pelat foto berisi citra bintang-bintang yang sudah diketahui posisinya berdasarkan katalog dan citra bintang-bintang yang belum diketahui posisinya. Posisi bintang yang ada di katalog dinyatakan dengan (a,3). Bintang yang belum diketahui posisinya lebih banyak jumlahnya daripada bintang yang sudah diketahui posisinya. Citra bintang pada pelat foto berupa sebuah titik dalam bentuk tetap. Posisinya pada pelat merupakan hasil pengukuran pada bidang kartesius dan dinyatakan dengan (1;,fl). Hasil pengukuran tersebut kemudian direduksi menjadi koordinat terukur (x,y). Hubungan antara (a,3) dan (x,y) didekati dengan sebuah deret dengan konstanta-konsranta deret merupakan konstanta pelat. Nilai konstanta pelat diperoleh dengan menggabungkan hasil pengukuran posisi bintang pada masing-masing pelat menjadi sebuah persamaan normal (Jefferys, 1963). Hasil akhir dari gugus persamaan normal tersebut dijabarkan dalam bentuk nOlasi matriks partisi dan berupa sebuah sistem persamaan linier Ax = b di mana A adalah matriks jarang, dan x merupakan konstanta pelar yang akan dicari nilainya. Untuk menyelesaikan sistem persamaan linier terse but digunakan metode transformasi given. Konstanta pelat yang sudah diperoleh dengan menyelesaikan sistem persamaan linier di atas, kemudian disubtitusi ke sebuah persamaan untuk memperoleh posisi bintang yang tidak tercantum dalam katalog. .
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