Judul: Aktivitas Ekstrak Kasar Tanin Daun Pepaya Dalam Mengurangi Ekspresi Gen Pembentuk Staphyococcal Enterotoxin A.
Abstrak: Daun pepaya banyak digunakan untuk mengempukkan daging karena memiliki enzim papain. Dalam aplikasinya daun pepaya sering digunakan untuk membungkus daging. Daun pepaya juga diketahui memiliki kemampuan antibakteri. Salah satu komponen bioaktif pada daun pepaya yang berperan sebagai anti bakteri adalah tanin. Tanin diketahui dapat menghambat pertumbuhan bakteri dengan merusak sel bakteri, salah satunya adalah Staphylococcus aureus. S. aureus dapat menyebabkan keracunan makanan karena menghasilkan enterotoxin. Salah satu enterotoxin yang dihasilkan disandikan oleh gen sea. Tanin juga dilaporkan dapat mengganggu metabolisme dengan berinteraksi dengan DNA Calf thymus. Tanin selain dapat menghambat pertumbuhan S.aureus diharapkan juga mampu berinteraksi dengan DNA S. aureus sehingga akhirnya dapat menyebabkan terhambatnya ekspresi penyandi gen sea. Penelitian ini bertujuan untuk membandingkan prosedur ekstraksi tanin dari daun pepaya, memverifikasi keberadaan gen sea pada 2 jenis isolat S.aureus (SJ1 dan S10), menentukan aktivitas antimikroba ekstrak kasar tanin terhadap S.aureus dan menentukan kemampuan ekstrak kasar tanin daun pepaya dalam mengurangi ekspresi gen sea secara relatif dengan menggunakan Reverse Transcriptase Real- Time PCR Ekstraksi ekstrak kasar tanin dari daun pepaya Calina dengan dilakukan dengan membndingkan metode kombinasi antara proses refluks dan maserasi dengan metode Ultrasound Assisted Extraction (UAE). Isolat S. aureus SJ1 dan S10 diverifikasi secara molekuler apakah merupakan penghasil SEA. Isolat ini selanjutnya digunakan pada tahapan penentuan aktivitas antimikroba ekstrak kasar tanin dengan metode cakram (konsentrasi 0 mg/mL, 50 mg/mL dan 100 mg/mL) dan pengenceran makro (konsentrasi 0 mg/mL, 5 mg/mL, 10 mg/mL dan 20 mg/mL), pemaparan S. aureus dengan ekstrak kasar tanin daun pepaya (konsentrasi 0 mg/mL, 5 mg/mL dan 10 mg/mL), serta pada pengukuran tingkat ekspresi gen sea secara relatif dengan qRT-PCR. Ekstraksi menggunakan metode kombinasi antara proses refluks dan maserasi menghasilkan jumlah rendemen yang lebih tinggi (4.27%) dibandingkan dengan menggunakan metode UAE (1.83%). Kultur SJ1 yang diisolasi dari sate jeroan dan S10 yang berasal dari susu sapi mentah positif merupaan bakteri S.aureus dilihat dari terbentuknya amplikon berukuran 240 pb dan positif merupaka penghasil SEA dilihat dari terbentuknya amplikon berukuran 120 pb. Selama 24 jam pemaparan, ekstrak kasar tanin hasil refluks dan maserasi dengan konsentrasi 20 mg/mL mampu menekan pertumbuhan S.aureus secara nyata. Pemaparan S.aureus dengan ekstrak kasar tanin konsentrasi 5 mg/mL dan 10 mg/mL selama 1 jam belum mampu menurunkan jumlah S.aureus namun mampu menurunkan jumlah ekspresi gen sea secara signifikan yaitu 6.65 kali dan 11.83 kali pada SJ1 serta 2.75 kalidan 4.35 kali pada S10.
Keyword: Daun pepaya, Ekspresi gen sea, S. aureus, SEA, Tanin

Judul: Pengaruh Paparan Ekstrak Kasar Alkaloid Daun Pepaya Muda Kering Beku terhadap Empat Isolat Staphylococcus aureus dan Ekspresi Gen sea
Abstrak: Staphylococcus aureus produces staphylococcal enterotoxin A (SEA) that causes food poisoning and resistant to the heating process. The presence of S. aureus and SEA on food could be detected by moleculer technique, its conducted quickly and accurately. Molecular detection is based on the genetic information of cell. Alkaloids are bioactive compound in young papaya leaves that can act as antimicrobials. The drying process and extraction method are greatly affecting the total alkaloid content in papaya leaves. Alkaloids as antimicrobial can acts by intercalating into cell wall and double-stranded DNA, and affecting topoisomerase enzymes and DNA-repairing enzymes. The aims of this research were to study the effect of drying methods of young papaya leaves to the yields of crude alkaloid extract, to identify toxin-producing of four S. aureus by molecular technique, and to identify the effect of crude alkaloid extract exposure towards S. aureus cells and relative expression of sea gene of four S. aureus isolated from food origin, i.e. raw milk (S10), balado eggs (TBI), stir-fried chicken intestine (UA13) and chicken offal satay (SJI). Drying of Calina young papaya leaves was conducted with the oven temperature of 55°C and freeze drying. Crude alkaloid extract were extracted by ultrasonication method and detected using Mayer’s reagent. S. aureus isolates that have been stored in ampoules were examined morphologically by growing them on baird parker agar (BPA) and triptyc soy agar (TSA) media. Antibiotic resistance was conducted towards S. aureus isolates using gentamicin, streptomycin, kanamycin, chloramphenicol, tetracycline and oxytetracycline. S. aureus isolates were molecularly detected with conventional PCR. The PCR results were sequenced to see the sequence of bases on each DNA, then the sequence was analyzed with Basic Local Alignment Search Tool http://blast.ncbi.nlm.nih.gov. Exposure of crude alkaloid extract with concentrations of 0.25 mg/ml and 0.5 mg/ml towards S. aureus was conducted for 2 hours. The cell number of S. aureus before and after 2-hour exposure was calculated using agar spread-plate method, then the relative expression of sea gene was measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR) method. Papaya leaves dryed with freeze drying method contained crude alkaloid extract content of 1.34±0.36%. These results were relative higher than the oven drying method that only produced 0.99±0.03% crude alkaloid extract, although statistically they were not significantly different. S10, TBI, UA13 and SJI isolates on BPA media has round-shaped colonies, smooth, convex and gray to black in color. The colonies’ surrounded edge was clear (with bright area). All isolates formed a yellow pigment on TSA media. All isolates were resistant to streptomycin. In addition, there was a different sensitivity of each bacteria toward antibiotic gentamicin, kanamycin, chloramphenicol, tetracycline and oxytetracycline. Analysis of isolates by conventional PCR showed that all isolates were positive for sea gene with the amplicon size 120 bp. S10, UA13 and TBI isolates have similarities with Staphylococcus aureus strain RKI4 and SJI isolate has similarities with S. aureus 08BA02176 genome in GenBank. Exposure of crude alkaloid extract obtained from freeze-dried young papaya leaves at 0.25 mg/ml and 0.5 mg/ml for 2 hours slightly reduced the cell number of S. aureus for approximately
Keyword: alkaloids, S. aureus, sea gene, real time PCR

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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