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: Aktivitas ekstrak kasar alkaloid daun pepaya terhadap Staphylococcus aureus dan ekspresi gen Staphylococcal enterotoxina
Abstrak: Papaya plant is widely grown in Indonesia. Papaya leaves are used by people as vegetable, meat tenderizer and traditional herbs. Extracts of papaya leaves have been reported to have antimicrobial activity against both Gram positive and Gram negative bacteria. This antimicrobial activity was related to phytochemical content of papaya leaves. Tannins and terpenoids can make cell membrane disruption, whereas alkaloids have been shown to intercalate into DNA and inhibit DNA synthesis. Therefore, besides as meat tenderizer, papaya leaves can be an alternative natural preservatives in food. Staphylococcus aureus is known pathogen causing intoxication by producing staphylococcal enterotoxins (SEs) in food. Staphylococcal enterotoxin A (SEA) is one of SEs that is commonly implicated in staphylococcal food poisoning. SEA is synthesized from sea gene and expressed from the midexponential phase of growth. In addition to the ability to inhibit S. aureus growth, there is a potential action of papaya leaves extract, i.e the ability to inhibit SEA production through the alkaloids activity. This study was conducted to investigate the ability of crude alkaloid extract from papaya leaves to inhibit SEA expression. Crude alkaloid extract was extracted from grounded dried papaya leaves using ultrasonic-assisted extraction. S. aureus was isolated from ready to eat food and raw cow milk using modified Bacteriological Analytical Manual (BAM) method. Isolates with typical colony of S. aureus on Baird-Parker Agar (BPA) and Mannitol Salt Agar (MSA) and produced coagulase were identified using API Staph test and PCR of 16S rRNA gene, followed by sequencing. Those 16S rRNA gene sequence were analyzed using BLAST. Minimum Inhibitory Concentration (MIC) of crude alkaloid extract were determined by broth macro-dilution method. Furthermore, S. aureus isolate was exposed to crude alkaloid extract at 0, 1, and 2 folds of MIC, and subsequently the expression of sea gene was analyzed using a quantitative reverse transcription PCR (qRT-PCR). The results demonstrated that the yield of crude alkaloid extracts was 0.48% to 1.82% per dry weight of papaya leaves. SEA-producing S. aureus were obtained from some foods, i.e raw milk, fried egg in chilli sauce, sauteed chicken intestine, and chicken liver satay. The MIC of crude alkaloid extract to S. aureus was 0.25 mg/ml. After exposure to the crude alkaloid extract at 0.25 mg/ml and 0.5 mg/ml for 2 h, significant increase in cycle threshold (CT) values of sea gene was observed. These results indicated a decrease of initial amount of sea cDNA which meant lesser mRNA was synthesized from the sea gene. The sea gene was expressed 29 and 41 times less when S. aureus was exposed to crude alkaloid extract at 1 and 2 folds MIC, respectively, determined relatively to the calibrator sample and an internal control using comparative CT method. The crude alkaloid extract of papaya leaves possessed antibacterial activity against S. aureus which was not only inhibited the bacteria but also the toxin formation by suppressing the expression of sea gene.
Keyword: crude alkaloid extract, papaya leaves, Staphylococcus aureus, staphylococcal enterotoxin A

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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