Judul: Kajian Pustaka Pengaruh Perbedaan Metode Ekstraksi Minyak Spirulina platensis Terhadap Profil Asam Lemak
Abstrak: Spirulina platensis merupakan mikroalga yang memproduksi asam lemak tidak jenuh dan asam lemak jenuh. Ekstraksi minyak S. platensis sudah dilakukan dengan berbagai macam metode, namun belum diketahui metode ekstraksi terbaik. Tujuan dari penelitian ini yaitu menganalisis dan membandingkan metode ekstraksi menggunakan soxhlet, Ultrasound Assisted Extraction, Microwave Assisted Extraction, dan Supercritical CO2 terhadap hasil rendemen dan profil asam lemak S. platensis berdasarkan kajian literatur. Hasil menunjukkan bahwa rendemen minyak tertinggi diperoleh pada metode Supercritical CO2 yaitu sebesar 9,36%, sedangkan yang terendah diperoleh pada metode soxhlet yaitu sebesar 2,25%. Total asam lemak tertinggi didapat pada metode Supercritical CO2 yaitu sebesar 100% yang menunjukkan bahwa metode tersebut menghasilkan minyak Spirulina dengan kemurnian tinggi., Spirulina platensis is one of microalgae that can produce saturated and unsaturated fatty acids. Extraction of S. platensis oil have been done in various methods. The aim of this research was to analyze and compare the oil extraction methods such as soxhlet, ultrasound assisted extraction, microwave assisted extraction, and supercritical CO2 regarding of its yield and fatty acids profile. The result showed that the highest oil yield obtained by Supercritical CO2 which was 9.36%, and the lowest oil yield obtained by soxhlet method 2.25%. However, the highest total fatty acids was obtained by Supercritical CO2 was 100%. Therefore, those methods resulted the highest purity of Spirulina oil.
Keyword: asam lemak, metode ekstraksi, Spirulina platensis

Judul: Extraction and Enzymatic Hydrolysis of Spirulina sp. Protein as Antioxidant Properties
Abstrak: Spirulina sp. merupakan mikroalga yang dikonsumsi sebagai dietary supplement karena memiliki kandungan gizi utama protein dan aktivitas biologis dalam menginhibisi senyawa radikal bebas. Proses ekstraksi dan hidrolisis protein diduga mampu meningkatkan sifat fungsional serta aktivitas inhibisi radikal bebas 1,1-diphenyl-2-picryl-hydrazyl (DPPH) Spirulina sp.. Tujuan penelitian ini membandingkan pengaruh perbedaan metode ekstraksi terhadap konsentrasi protein, derajat hidrolisis, inhibisi radikal bebas DPPH, serta profil asam amino hidrolisat Spirulina sp.. Spirulina sp. diekstrak dengan metode fisik dan metode kimiawi. Ekstrak yang dihasilkan kemudian dianalisis konsentrasi protein dan dihidrolisis dengan enzim papain, lalu dianalisis derajat hidrolisis dan profil asam amino. Ekstrak dan hidrolisat Spirulina sp. dianalisis inhibisi radikal bebas DPPH pada hari ke-0 dan ke-210 setelah proses hidrolisis. Perbedaan metode ekstraksi berpengaruh signifikan (p < 0,05) terhadap konsentrasi protein ekstrak. Metode fisik menghasilkan ekstrak dengan konsentrasi protein 67,4 ± 14,35 mg/mL, sedangkan metode kimiawi 53,41 ± 3,90 mg/mL. Perbedaan metode ekstraksi berpengaruh signifikan (p < 0,05) terhadap derajat hidrolisis hidrolisat yang dihasilkan. Hidrolisat yang diekstrak dengan metode fisik memiliki derajat hidrolisis 77,14 ± 11,95%, sedangkan metode kimiawi 35,08 ± 15,88%. Hidrolisat dan ekstrak Spirulina sp. mengalami penurunan nilai inhibisi radikal bebas setelah penyimpanan beku. Kandungan asam amino hidrolisat ekstrak metode fisik yaitu 8.711,56 mg/kg, sedangkan metode kimiawi sebesar 3.391,56 mg/kg., Spirulina sp. is a microalgae species that is consumed as a dietary supplement due to its high nutrition content, especially protein and its bioactivity as a radical scavenger. Extraction and hydrolysis processes are expected to enhance Spirulina’s functional characteristic and its bioactivity to inhibit free radicals 1,1-diphenyl-2-picryl-hydrazyl (DPPH). The aim of this study was to compare the effect of two different extraction methods on protein concentration, degree of hydrolysis, DPPH free radical inhibition, and amino acid profile of Spirulina sp. hydrolysate. Spirulina sp. were extracted using two different methods, physical and chemical methods. The crude protein extracts was analyzed using Biuret method and hydrolysed using papain enzyme. The protein hydrolysate was finally run through some analysis such as hydrolysis degree, amino acid profile, and DPPH scavenging activity. The two different extraction methods effected on protein concentration and degree of hydrolysis significantly (p < 0,05). Protein concentration of Spirulina sp. that were extracted using physical method is 67,4 ± 14,35 mg/mL, while Spirulina sp. that were extracted using chemical method is 53,41 ± 3,90 mg/mL. Hydrolysis degree of protein hydrolysate extracted using physical method is 77,141 ± 11,945% while Spirulina sp. that were extracted using chemical method is 35,081 ± 15,884%. Both Spirulina sp. extract and hydrolysate %inhibition decreased after storage. Hydrolysate extracted using physical method contains 8.711,56 mg/kg of amino acid, while hydrolysate extracted using chemical method contains 3.391,56 mg/kg.
Keyword: DPPH radical inhibition, extraction, papain, protein, protein hydrolysate

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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