Judul: Isolation and Characterization of Protease Keratinolytic Enzyme in Water Monitor Lizard Intestine.
Abstrak: Protease enzyme isolated from mucosa layer in intestine water monitor lizard (Varanus salvator) showed proteolytic activity. Therefore, the purpose of this research was to isolate and characterize of protease produced by water monitor lizard intestine. The intestine mucous layer of water monitor lizard (2%) was dissolved in 50mM buffer phosphate pH 7,0, then centrifuged at 6000 G in 4 ºC temperature for 10 minute. The centrifuged extract was used to analyze the maximum enzyme activity by heating the extract at 45–65 ºC range temperature and 5–20 minute range time. Maximum enzyme activity analysis obtained at 55 ºC for 5 minute for the sample duodenum, jejunum, ileum, colon respectively were 4, 3482 U/ml, 3,9247 U/ml, 3,9176 U/ml, and 3,0353 U/ml. Protease from extract enzyme has seven bands with molecular weight 66,54 kDa, 57,61 kDa, 48,94 kDa, 48,47 kDa, 36,80 kDa, 24,28 kDa, and 12,80 kDa. The enzyme has optimum temperature at 55 ºC and optimum at pH 9, and also inhibited by ion Ca2+ and Mg2+ . The in vitro analysis used chicken powder showed no keratinase activity.
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Judul: Isolation of proteolytic bacteria from Gili Meno Lake, West Nusa Tenggara and characterization protease enzyme
Abstrak: Keanekaragaman hayati Indonesia yang cukup besar merupakan potensi dalam pengembangan produksi enzim. Adanya upaya pencarian mikroorganisme indigenos penghasil enzim dapat memungkinkan Indonesia sebagai salah satu produsen enzim. Penelitian ini bertujuan untuk mengisolasi dan menyeleksi bakteri proteolitik yang berasal dari danau Gili Meno serta mengkarakterisasi enzim protease dari isolat yang terpilih. Sebanyak 52 isolat bakteri proteolitik berhasil diisolasi dari sampel tanah dan sedimen danau. Media yang digunakan berupa media cair Nutrient broth (NB) dan media padat nutrient agar (NA) yang ditambahkan susu skim 1%. Isolat LG 18 dan LI 2 dipilih untuk produksi enzim karena memiliki aktivitas spesifik tertinggi. Aktivitas spesifik tertinggi isolat LG 18 dicapai pada jam ke-9. Protease isolat LG 18 optimum pada pH 6 dan suhu 40°C. Penambahan kation Ca2+, Cu2+, Na+ dan Co2+ umumnya menurunkan aktivitas protease isolat, sementara penambahan kation logam Zn2+ 2 mM tidak berpengaruh nyata terhadap aktivitas protease isolat . Aktivitas spesifik tertinggi isolat LI 2 dicapai pada jam ke-12. Protease isolat LI 2 optimum pada pH 6 dan suhu 45°C dan aktivitasnya ditingkatkan hingga 123,88% oleh Co2+ pada konsentrasi akhir 2 mM. Kation lainnya yaitu Ca2+, Cu2+, Na+ dan Zn2+ umumnya menurunkan aktivitas protease isolat. Protease kedua isolat diduga merupakan metaloprotease karena aktivitasnya dihambat hingga lebih dari 50% dengan senyawa pengkelat logam ethylene diamine tetraacetic acid (EDTA) pada konsentrasi akhir 2 mM dan 5 mM.
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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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