Judul: Imobilisasi Lipase Rhizopus Oryzae Pada Berbagai Bahan Pendukung Untuk Produksi Diasilgliserol Dari Cpo.
Abstrak: Diasilgliserol (DAG) dikategorikan sebagai salah satu minyak sehat yang telah dijadikan menu diet sehari-hari oleh masyarakat terutama di Jepang. Selain itu, DAG telah dimanfaatkan sebagai emulsifier dan surfaktan makanan serta digunakan dalam bidang farmasi dan kedokteran. DAG dapat diproduksi dari Crude Palm Oil (CPO) yang ketersediannya melimpah di Indonesia. Namun produksi DAG di Indonesia terkendala oleh tingginya harga lipase yang masih diimpor. Untuk mengatasi masalah tersebut, telah dilakukan penelitian produksi DAG menggunakan ekstrak kasar lipase yang dihasilkan oleh fungi lokal Rhizopus oryzae. Fungi R. oryzae ini bersifat edible sehingga aman untuk dimanfaatkan dalam produksi produk pangan seperti DAG. Imobilisasi enzim merupakan teknik perolehan kembali enzim yang menjadi perhatian dalam beberapa tahun belakangan, dilakukan dengan bantuan bahan pendukung sebagai media yang dapat mencegah terlarutnya enzim. Beberapa macam pendukung yang digunakan ialah zeolit, CaCO3, silika gel dan tulang sapi. Metode imobilisasi yang digunakan dalam penelitian ini ialah metode adsorpsi, menggunakan lipase spesifik dari R. oryzae. Penentuan protein enzim dilakukan untuk mengetahui jumlah enzim yang teradsorpsi pada berbagai bahan pendukung dengan metode Bradford menggunakan spektrofotometri UV-Vis. Konsentrasi enzim imobil diperoleh dari selisih konsentrasi larutan lipase sebelum proses imobilisasi, larutan lipase setelah proses imobilisasi dan larutan pencuci. Dalam penelitian ini, diselidiki faktor dari setiap bahan pendukung seperti pH optimum, suhu optimum, dan waktu penyimpanan. Aktivitas lipase dihitung dengan penentuan asam lemak bebas menggunakan metode titrasi. Komposisi asam lemak bebas, monoasilgliserol, diasilgliserol, dan triasilgliserol pada proses gliserolisis diidentifikasi menggunakan TLC Scanner. CaCO3 memiliki kemampuan adsorbsi terbesar (99,46%), lebih besar dibandingkan zeolit (90,69%), tulang sapi (91,56%), dan silika gel (59,63%). Lipase bebas bekerja optimal pada pH 7 dan suhu 30 °C. Hasil yang sama didapatkan untuk lipase terimobilisasi pada tulang sapi. Lipase terimobilisasi pada CaCO3 bekerja optimal pada pH 8 dan suhu 35 °C. Lipase terimobilisasi pada zeolit dan silika gel bekerja optimal pada pH 8 dan suhu 30 °C. Lipase imobil lebih stabil dibandingkan lipase bebas pada penyimpanan lipase di minggu pertama hingga minggu ke enam, dengan kondisi penyimpanan pada suhu 4 °C dan pH optimum masing-masing bahan pendukung. Lipase terimobilisasi pada CaCO3 dapat digunakan kembali hingga tiga kali pengulangan. Konversi gliserolisis lipase terimobilisasi CaCO3 mencapai 15,02% selama 9 jam lebih rendah dibandingkan menggunakan lipase bebas sebesar 18,41% selama 15 jam.
Keyword: Diasilgliserol, Imobilisasi, Lipase, Rhizopus oryzae

Judul: Optimation of Enzymatic Diacylglycerol Production from CPO with Continuous Systems
Abstrak: Diacylglycerol (DAG ) is categorized as one of the healthy oil types that has been used in daily diet by the society, especially in Japan. In addition, the DAG has been used as an emulsifier and surfactant in the food and in pharmaceutical and medical fields (Anggirasti et al. 2008; Noureddini et al. 2004) . DAG can be produced from Crude Palm Oil (CPO) that is abundantly produced in Indonesia. However, DAG production in Indonesia is constrained by the high cost of lipase that is still imported from abroad. To overcome this problem, research of DAG production has been conducted using crude extract of lipase produced by indigenous species of fungi Rhyzopus oryzae. The R. oryzae is edible indicating that it is safe to be used in the production of food products such as DAG. This study was aimed to automate the process of enzymatic glycerolysis in DAG production carried out using continuous system; to establish optimum conditions for DAG production through continuous glycerolysis which includes flow rate of CPO, glycerolysis time and the form of lipase for catalyzing the glycerolysis process; and to test the performance of lipase from indigenous fungi R. oryzae in catalyzing glycerolysis using continuous process for the production of DAG. The process of continuous glycerolysis was carried out in a bioreactor by reacting glycerol with CPO substrate in a hexane solvent that flowed continuously with a peristaltic pump and catalyzed by lipase dissolved in Tris-HCl buffer. The lipase used was in the form of free lipase (dissolved in buffer) and immobilized lipase (adsorbed in the zeolite). The process of continuous glycerolysis was carried out with variations of substrate (CPO) flow rate, i.e 1 and 3 mL/min and variations of glycerolysis time, using time increment of 3 hours for 24 hours. The results showed that the designed automation system for glycerolysis process was successful. The process of glycerolysis could run automatically, making the process could be run more easily, quickly and efficiently. The optimum conditions for continuous production of DAG via glycerolysis was achieved at the CPO flow rate of 3 mL/min, glycerolysis time at the 9th hour with free lipase which was two times faster than that from previous research with batch systems, and at the 21th hour with immobilized lipase, possibly due to immobilized lipase demonstrated increased stability during glycerolysis than free lipase. Products conversion of DAG was 29 % with free lipase and 33 % with immobilized lipase. In the process of continuous glycerolysis, substrate replacement treatment was also carried out 3 times to observe the performance of lipase in catalyzing the process of glycerolysis, and the results showed that lipase from indigenous mold R. oryzae was able to catalyze the glycerolysis process in hydrolysis or esterification reactions to form DAG products. This CPO substrate replacement treatment for 3 times caused an increase in conversion of DAG products to 37 %, it is suspected because of the new supply/acyl donor derived from each CPO substrate that replaced 3 times in the process of glycerolysis. A decrease in the stability of the immobilized lipase after 3
Keyword: continuous glycerolysis, CPO, diacylglycerol, lipase, Rhizopus oryzae

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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