Judul: Extraction of Heparin from Tuna Gut (Thunnus sp.)
Abstrak: Heparin merupakan polisakarida linier dengan gugus sulfat yang terkenal kegunaannya sebagai obat antikoagulan. Heparin umumnya diperoleh dari jaringan hewan mamalia seperti sapi dan babi yang memungkinkan terdapatnya kontaminan seperti spora bovine encephalitis penyebab penyakit sapi gila serta dilarang pada beberapa kepercayaan dan agama. Penelitian ini menggunakan limbah perikanan yaitu jeroan ikan tuna sebagai sediaan antikoagulan heparin. Penelitian bertujuan untuk menentukan konsentrasi enzim papain terbaik untuk ekstraksi heparin dari bagian jeroan ikan tuna yang berbeda, mendapatkan karakteristik terpilih dari heparin terfraksinasi bagian jeroan ikan tuna berbeda dan menentukan aktivitas antikoagulannya. Heparin diekstraksi menggunakan enzim papain berkonsentrasi 20, 40 dan 60 U/mL dalam kondisi larutan pH 8 serta difraksinasi dengan larutan aseton. Konsentrasi ekstrak heparin kasar yang terpilih yaitu hasil ekstraksi dari jeroan bagian lambung dengan enzim papain 40 U/mL. Heparin terfraksinasi yang diuji menggunakan FTIR menunjukkan karakteristik gugus fungsi yang mencirikan seperti heparin, namun aktivitas antikoagulannya masih bersifat lemah., Heparin is a linear polysaccharide with a sulfate group which is used as an anticoagulant drug. Generally, heparin is obtained from mammalian animal tissues such as cattle and pigs, which allows the presence of contaminants such as bovine encephalitis that cause mad cow disease and is prohibited in some religions. This research used tuna manufacturing waste, which is tuna gut as the raw material for preparing heparin. The aim of the study was to determine the best papain enzyme concentration for the extraction of heparin from different parts of tuna gut, to obtain the characteristics of selected pure heparin derived from different parts of tuna gut and to determine the anticoagulant activity of selected heparin. Heparin was extracted using papain enzymes with concentrations of 20, 40 and 60 U/mL in a solution of pH 8 and fractionated with acetone solution. The selected fractionated heparin for the anticoagulant activity test was from tuna’s stomach extracted with 40 U/mL papain enzyme. Compound from tuna gut showed the characteristics of heparin-like functional group and exhibited low anticoagulant activity.
Keyword: anticoagulant, chemical structure, concentration, fish gut, heparin

Judul: Collagen Extraction of Yellowfin Tuna (Thunnus albacares) Skin Using Pepsin and Papain Enzymes
Abstrak: Kolagen merupakan senyawa protein rantai panjang yang tersusun atas asam amino alanin, arginin, lisin, glisin, prolin, serta hiroksiprolin. Kolagen merupakan protein jaringan ikat yang dapat dihasilkan dari limbah kulit ikan. Tujuan penelitian ini untuk menentukan nilai aktivitas spesifik enzim pepsin yang diekstraksi dari lambung ikan tuna serta menentukan karakteristik kolagen yang diekstraksi dengan metode enzimatis. Metode penelitian terbagi menjadi 2 tahap yaitu tahap ekstraksi enzim pepsin dari lambung ikan tuna sirip kuning dan tahap ekstraksi kolagen kulit tuna dengan metode enzimatis. Enzim pepsin yang diekstraksi dari lambung tuna sirip kuning memiliki nilai aktivitas spesifik 8680 U/mg. Waktu perendaman dengan NaOH terbaik adalah 12 jam. Waktu Hidrolisis kulit dengan asam asetat terbaik adalah 72 jam. Kolagen larut papain memiliki bobot molekul 310 kDa, gugus fungsi amida A, B, I, II, dan III,dengan rendemen 2,13%. Kolagen larut pepsin sebagian memiliki bobot 328 kDa, gugus fungsi amida A, I, II, dan III, dengan rendemen 0,8%. Hidrolisat kolagen larut pepsin memiliki bobot molekul 69 kDa, gugus fungsi amida A, I, dan III, dengan rendemen 32%., Collagen is a long-chain protein compound composed of the amino acids alanine, arginine, lysine, glycine, proline, and hydroxyproline. Collagen is a connective tissue protein that can produce from fish skin waste. The purpose of this study was to determine the specific activity value of the pepsin enzyme extracted from the stomach of tuna and to determine the characteristics of the collagen extracted by the enzymatic method. The research method was divided into 2 stages, namely the extraction stage of the pepsin enzyme from the stomach of yellowfin tuna and the extraction stage of tuna skin collagen using the enzymatic method. The pepsin enzyme extracted from the stomach of yellowfin tuna has a specific activity value of 8680 U / mg. The best soaking time with NaOH is 12 hours. Hydrolysis time of skin with acetic acid is best 72 hours. Papain soluble collagen has a molecular weight of 310 kDa, amide functional groups A, B, I, II, and III, with a yield of 2,13%. Pepsin soluble collagen partly weighed 328 kDa, amide functional groups A, I, II, and III, with a yield of 0,8%. Pepsin soluble collagen hydrolyzate has a molecular weight of 69 kDa, amide functional groups A, I, and III, with a yield of 32%.
Keyword: papain, pepsin, extraction, collagen

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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