Judul: Produksi dan Karakterisasi Enzim Tanin Asil Hidrolase dari Aspergillus niger.
Abstrak: Tannin acyl hydrolase (tannase) is a hydrolytic enzyme that acts on tannins. The application of tannase is mostly in food and medical industries. This research is aimed to produce and characterize tannase from Aspergillus niger isolated from pod cacao. The first step of this research includes determination of optimal pH, temperature and incubation period to produce tannase. Optimal tannase production was obtained at pH 5.5, 28 oC and incubation period of 3 days. Afterthat, production media optimization was conducted. The tested media were solid and liquid media with inducer concentration varied at 0, 3, 5 and 7%. The best media obtained was the solid media with tannic acid concentration as inducer of 5%. The next step was tannase fractionation by ammonium sulphate which was followed by dialysis process. The saturation le vel of ammonium sulphate used was 30-80% where the best activity obtained was at the saturation level of 60%. Compared to that of crude enzyme, specific activity of tannase after dialysis was four folds. Characterization results showed that optimum activity was at 35-50 oC and pH 6. Tannase was activated by K+ and Na+ with concentration of 10 and 50 mM, while Mg2+ ion could activate only at 10 mM. The addition metal ions like Zn2+, Cu2+, Ca2+, Mn2+ and Fe2+ inhibited the enzyme activity. From test of variation of substrate, it was found that the Km value of tannic acid and gallotannin was 0.401 and 6.611 mM respectively. While the Vmax value of tannic acid was 10.804 U/ml and gallotannin was 12.406 U/ml. Based on the Michaelis- Menten constant (Km), tannase of obtained in this research was more active in hydrolysing depsid bonds rather than ester bonds.
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Judul: Pemanfaatan Limbah Padat Kacang Hijau Untuk Produksi Enzim- Emilase, Amiloglukosidase Dan Selulase Dari Aspergillus niger Dan Aspergillus oryzae
Abstrak: Penelitian ini bertujuan untuk mempelajari pemanfaatan limbah padat kacang hijau sebagai media fermentasi untuk menghasilkan enzim damilase, amiloglukosidase dan selulase dari Aspergillus niger dan Aspergillus oryzae. A. niger L-51 dan A. oryzae L-54 masing-masing ditum- buhkan pada media limbah padat kacang hijau yang ditambah dengan air suling, atau larutan mineral yang mengandung NaH2PO4, CaCl2, KCl, dan MgCl2 dengan konsentrasi masing- masing sebesar 4.7, 0.1, 0.02, dan 0.02 persen. Jenis fer- mentasi yang digunakan adalah fermentasi media padat dan media cair. Setelah waktu inkubasi yang ditetapkan selama dua, lima, dan sembilan hari dicapai, enzim yang dihasilkan dipanen dan diuji aktifitasnya. Juga dilakukan pengukuran pH dan kadar protein terlarut di dalam filtrat enzim. Secara umum fermentasi media cair menghasilkan aktifitas enzim d-amilase, amiloglukosidase dan selulase yang lebih baik, kecuali untuk amiloglukosidase dari A. oryzae L-54 fermentasi media padat menghasilkan aktifitas enzim yang lebih baik. Semakin lama waktu inkubasi, aktifitas enzim d-amilase yang dihasilkan semakin rendah, sedangkan aktifitas enzim amiloglukosidase menunjukkan peningkatan sampai hari kelima kemudian menurun kembali, sebaliknya aktifitas enzim selu- lase menurun sampai hari kelima kemudian meningkat kembali. A. niger L-51 menghasilkan aktifitas enzim d-amilase tertinggi sebesar 5.203 unit/ml filtrat enzim atau 7.310 unit/mg protein pada fermentasi media cair dengan penambah- an air suling dan waktu inkubasi dua hari. Dengan waktu inkubasi yang sama diperoleh aktifitas enzim d-amilase ter- tinggi dari A. oryzae L-54 sebesar 4.877 unit/ml filtrat enzim 5.022 unit/mg protein pada fermentasi media cair de- ngan penambahan larutan mineral…dst
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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