Judul: Optimation of Unsaturation Level Increase of Crude Palm Oil with Desaturase by Using Continuous Systems
Abstrak: Desaturase is the catalyst for the formation of the double bond carbon chains either monounsaturated fatty acids (MUFA) or polyunsaturated fatty acid (PUFA). Desaturase producing fungi can be used to increase the unsaturation of crude palm oil (CPO). In the present study the fungi used was Rhizopus oryzae, because it is edible. The purpose of this study was to test the ability of Rhizopus oryzae in producing desaturase, extending enzyme-substrarate contact time, and increasing unsaturation of crude palm oil using bioreactor system model of spiral hose with height variation. First, the fungi were cultured in liquid media with supplements containing certain salts and CPO using Erlenmeyer. After incubation, the culture supernatant was separated from the biomass (liquid fermentation). Liquid fermentation was transferred into a bioreactor system model of continuous spiral hose with height variations (50 cm, 100 cm, 150 cm, 200 cm and 250 cm). Palm oil was pumped from the bottom of the column using a peristaltic pump. CPO was then characterized by determining the iodine number, saponification number, acid number and fatty acid composition both before and after the bioconversion. The results showed that Rhizopus oryzae fermentation liquid was able to increase the unsaturation CPO and multiple unsaturated fatty acid content. On studied conditions, the maximum unsaturation increase occurred at a height of 200 cm with iodine value change of 17.091 g I2/100g CPO with the contact time for 35 minutes. This indicated that the longer the contact time, the higher the unsaturation of CPO. Iodine number could also decrease due to the oxidation of the C = C double bond, that was indicated from the results of iodine number at a height of 250 cm with iodine value change of 15.886 g I2/100g CPO for contact time of 47 minutes. At the optimum conditions, the saponification number was 183.489 g KOH/g CPO and acid number was 9.36 g KOH/g CPO with levels of free fatty acids (% FFA) of 0.936%. Fatty acid composition of palm oil after optimum bioconversion conditions showed increase in oleic acid, and linoleic acid.
Keyword: polyunsaturated fatty acid, liquid fermentation, desaturase enzymes, Rhizopus oryzae, and continuous systems

Judul: Continuous Desaturation of Crude Palm Oil (CPO) Using Immobilized Desaturase in Semipilot Scale
Abstrak: Enzim desaturase adalah enzim yang mengkatalisis pembentukan ikatan rangkap pada rantai karbon asam lemak. Desaturase dapat dimanfaatkan untuk meningkatkan kualitas minyak sawit kasar (crude palm oil atau CPO) serta menghasilkan asam - asam Iemak tak jenuh yang bernilai ekonomis tinggi. Desaturase termasuk enzim intraseluler dan memiliki stabilitas yang rendah ketika berada di luar sel (in vitro). Salah satu usaha yang dapat dilakukan untuk meningkatkan stabilitas desaturase adalah dengan cara amobilisasi. Penelitian ini bertujuan untuk mendapatkan metode proses desaturasi kontinyu CPO terbaik dengan menggunakan desaturase amobil pada skala semipilot. Enzim desaturase diperoleh dari biomassa Absidia corymbifera yang dihancurkan menggunakan blender dalam larutan PBS (Phosphat Buffer·Saline). Larutan enzim dalam PBS dipisahkan dari biomassa dengan cara penyaringan. Larutan desaturase yang telah disaring diamobilisasi menggunakan butiran zeolit. Kemudian enzim yang telah teradsorbsi dalam zeolit digunakan dalam biokonversi kontinyu dengan metode packed bed reactor (PBR) dengan substrat berupa CPO yang dialirkan dari bawah ke atas (upward flow). Aktivitas desaturase amobil diperoleh dari peningkatan bilangan iod substrat yaitu CPO. Zeolit yang digunakan sebagai padatan pengamobilisasi terdapat dalam 2 ukuran yaitu zeolit kecil dengan diameter padatan 1 - 3 mm dan zeolit besar dengan diameter padatan 8 - 10 mm. Proses desaturasi kontinyu dilakukan dengan variasi waktu kontak 30 dan 40 menit. Penentuan metode proses terbaik dilakukan berdasarkan aktivitas enzim rata - rata pada rentang waktu yang dianggap stabil. Penggunaan z, Desaturase is an enzyme that catalyses the formation of double bonds in the fatty acid chains. Desaturase can be used to improve the quality of CPO and to produce unsaturated fatty acids that have high economical value. Desaturase is an intracellular enzyme and is very unstable when it is outside of the cell (in vitro). Immobilization is an effort to improve the stability of desaturase. The objective of this research was to obtain the method for continuous desaturation of crude palm oil (CPO) by using immobilized desaturase in semipilot scale. Desaturase enzyme was obtained from Absidia corymbifera biomass by extraction with Phosphate Buffer Saline (PBS) using a blender. The desaturase broth was separated from the biomass by filtration. Desaturase extract was immobilized by using zeolite. Then immobilized enzyme was used in the continuous bioconversion by using packed bed reactor (PBR) method. The substrate (CPO) was pushed from the bottom to the top of the coloumn (upward flow). The activity of immobilized desaturase was determined from the increase of iodine number of the CPO. There were two sizes of granulated zeolite used for immobilization, small zeolite (1 -3 mm) and large zeolite (8 -10 mm). Continuous desaturation process was done with the variation in contact time 30 and 40 min. Selection of the best process was based on the average enzyme activity in stable period.
Keyword: Minyak sawit kasar

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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