Judul: Antimicrobial, Antioxidant, and Toxicity Activity of Marine Actinomycetes Biopigment Extract
Abstrak: Aktinomiset merupakan bakteri Gram-positif yang mempunyai potensi sebagai sumber metabolit sekunder baru. Salah satu metabolit sekunder tersebut adalah biopigmen. Biopigmen yang dihasilkan oleh aktinomiset mempunyai berbagai aktivitas biologis. Penelitian ini bertujuan menguji kemampuan antimikrob, antioksidan, dan toksisitas ekstrak biopigmen aktinomiset laut kode HV11.P3 dan SCA54.P2. Aktivitas antimikrob diuji terhadap beberapa mikrob patogen dan menunjukkan hasil terbaik dalam menghambat pertumbuhan Bacillus subtilis ATCC 19659 untuk ekstrak HV11.P3 kemudian Escherichia coli ATCC 8739 untuk SCA54.P2.Aktivitas antioksidan terhadap radikal DPPH menunjukkan nilai IC50 231,084 μg/ml untuk HV11.P3 dan 369,296 μg/ml untuk SCA54.P2. Hasil uji toksisitas berupa nilai LC50 yaitu 94,603 μg/ml untuk HV11.P3 dan 131,220 μg/ml untuk SCA54.P2 menggunakan metode Brine Shrimp Lethality Test (BSLT). Senyawa kimia penyusun ekstrak diidentifikasi menggunakan GC-MS. Hasilnya senyawa 1H-Purine-2,6-dione, 3,7-dihydro-1,3,7-trimethyl- (CAS) menjadi penyusun dominan ekstrak HV11.P3 dengan peak area 44,65% dan 5-Methoxypyrrolidin-2-one dengan luas peak area 30,23% untuk ekstrak biopigmen SCA54.P2. Analisis gen 16S rRNA menunjukkan bahwa HV11.P3 memiliki kesamaan terdekat dengan Micromonospora chalcea strain 1464-217L dan SCA54.P2 dengan Micromonospora tulbaghiae strain TVU1., Actinomycetes are Gram-positive bacteria that have potency as a source of new secondary metabolites. One of those secondary metabolites is biopigments. Biopigments produced by actinomycetes have various biological activities. This study aimed to determine antimicrobial, antioxidant, and toxicity activity from marine actinomycetes biopigment extract coded as HV11.P3 and SCA54.P2. Antimicrobial activities were tested against several pathogenic bacteria and showed the best result for inhibiting Bacillus subtilis ATCC 19659 for HV11.P3 and Escherichia coliATCC 8739 for SCA54.P2. The antioxidant activity against DPPH radical showed IC50 value 231,084 μg/ ml for HV11.P3 and 369,296 μg/ ml for SCA54.P2. The toxicity test results (LC50) based on Brine Shrimp Lethality Test (BSLT) were 94,603 μg/ ml and 131,220 μg/ ml for HV11.P3 and SCA54.P2, respectively. The major chemical compounds of HV11.P3 extract were identified as 1H-Purine-2,6-dione, 3,7-dihydro-1,3,7-trimethyl- (CAS) (peak area 44,65%) and 5-Methoxypyrrolidin-2-one for SCA54.P2 (peak area 30,23%). The 16S rRNA gene analysis showed that HV11.P3 had the closest similarity with Micromonospora chalcea strain 1464-217L and SCA54.P2 with Micromonospora tulbaghiae strain TVU1.
Keyword: BSLT, DPPH, Extract, GC-MS, 16S rRNA gene

Judul: Antioxidant Activity of Black Biopigment Extract from Micromonospora fulva HV4.P3
Abstrak: Aktinomiset merupakan bakteri gram positif berfilamen dengan ciri khas yakni adanya kandungan pasangan basa GC yang tinggi pada DNA-nya. Mikrorganisme ini memiliki habitat yang luas, baik di darat atau laut. Aktinomiset laut yang berasosiasi dengan spons dapat menghasilkan senyawa bioaktif sebagai metabolit sekunder, salah satunya biopigmen. Beberapa jenis biopigmen diketahui memiliki bioaktivitas yang beragam salah satunya antioksidan. Penelitian ini bertujuan untuk menentukan aktivitas antioksidan dari ekstrak biopigmen aktinomiset Micromonospora fulva strain HV4.P3 yang berasosiasi dengan spons. Tahapan dalam penelitian ini meliputi peremajaan isolat aktinomiset, identifikasi aktinomiset menggunakan penanda gen 16S rRNA, ekstraksi biopigmen, uji aktivitas antioksidan, dan analisis kandungan senyawa bioaktif menggunakan alat Gas Chromatography-Mass Spectrometry (GC-MS). Aktivitas antioksidan diuji dengan menggunakan metode 2,2-diphenyl-1-picrylhydrazyl (DPPH). Hasil identifikasi aktinomiset menunjukkan bahwa isolat HV4.P3 memiliki nilai similaritas tertinggi dengan Micromonospora fulva UDF-1 sebesar 98.32%. Aktivitas antioksidan ekstrak biopigmen tersebut memiliki nilai IC50 sebesar 195.772 ± 2.3 μg/mL. Hasil analisis komponen kimia menggunakan GC-MS menunjukkan bahwa biopigmen aktinomiset ini didominasi oleh senyawa sulfinylbis dengan kelimpahan sebesar 2.95 %., Actinomycetes are filamentous gram-positive bacteria with a specific characteristic that is the presence of a high content of GC base pairs in their DNA. These microorganisms have a wide habitat, either on land or sea. Marine actinomycetes associated with sponges can produce bioactive compounds as secondary metabolites, one of which is biopigment. Several types of biopigments are known to have various bioactivities, such as antioxidants. This study aimed to determine the antioxidant activity of the actinomycete biopigment extract Micromonospora fulva HV4.P3. This study’s step including the re-culture of actinomycetes, identification of actinomycetes using the 16S rRNA gene, extraction of biopigments, antioxidant activity test, and identification of bioactive compounds inside particular biopigment using Gas Chromatography-Mass Spectrometry (GC-MS). Antioxidant activity was tested using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The results of actinomycete identification showed that the HV4.P3 isolate had the highest similarity with Micromonospora fulva UDF-1 with a value of 98.32%. The antioxidant activity of the biopigment extract has an IC50 value of 195.772 ± 2.3 μg g/mL. The analysis of chemical components using the GC-MS identified that the actinomycete biopigment was dominated by the compound of sulfinylbis with an abundance value of 2.95%.
Keyword: biopigmen, DPPH, GC-MS, Micromonospora fulva

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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