Judul: Uji aktivitas antioksidan lignin dari tandan kosong kelapa sawit
Abstrak: The increasing oil palm plantation will increase the amount of oil palm production. One of the solid waste from oil palm industry is empty fruit bunch (EFB) that contain lignocellulose. This research used lignin content in EFB as an antioxidant. Lignin delignification from EFB was done by pulping organosolv method using ethanol. Lignin antioxidant activity was characterized with DPPH method (1,1-diphenyl-2-picrylhydrazyl) as free radical, measured as IC50 (inhibition concentration 50%). Lignin yield was 9,09%; lignin content 76,57%; and fourier transform infrared (FTIR) spectrum indicated the lignin. Phenolic hydroxyl and molecular weight lignin were also determine the lignin antioxidant activity. This result pointed out that the lignin have phenolic structure of type 2 and 3 each 0,4% and the molecular weight is 4005 g/mol. Butylated hydroxytoluene (BHT), a commercially chemical antioxidant, was used as a positive control. The IC50 of lignin is 50,2 ppm, while IC50 that of BHT is 1883 ppm. This result shows that antioxidant activity of lignin is higher than that of BHT.
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Judul: Aktivitas Antimikroba dan Antioksidan Nanolignin dari Tandan Kosong Kelapa Sawit.
Abstrak: Lignin merupakan polimer alam yang banyak dijumpai pada bahan berlignoselulosa bersama selulosa dan hemiselulosa. Penelitian ini bertujuan untuk menguji aktivitas antimikroba dan aktivitas antioksidan lignin dan nanolignin dari Tandan Kosong Kelapa Sawit (TKKS). Pada awalnya, isolasi lignin dilakukan pada TKKS dengan NaOH 10% (b/v) dan dilanjutkan dengan pengendapan menggunakan H2SO4 dengan perlakuan konsentrasi 10, 20 dan 30% (v/v). Lignin yang diperoleh dari proses sebelumnya dilakukan ultrasonikasi untuk mendapatkan lignin berukuran nano (nanolignin). Fourier Transform Infrared (FTIR) spectroscopy dilakukan untuk mengetahui keberhasilan isolasi lignin dan nanolignin serta Scanning Electron Microscope (SEM) dilakukan untuk mengetahui ukuran lignin setelah diultrasonikasi. Penentuan aktivitas antimikroba pada lignin dan nanolignin dilakukan dengan menggunakan metode difusi sumur bakteri Salmonella typhimurium ATCC 14028, Bacillus subtilis ATCC 19059, dan Escherichia coli ATCC 25922, serta diuji aktivitas antioksidannya dengan metode DPPH (2,2-diphenyl-1-picryl-hydrazyl). Hasil FTIR menunjukkan bahwa hasil isolasi lignin berhasil. Namun, hasil SEM belum menunjukkan lignin perlakuan ultrasonikasi berukuran nano (1-100 nm). Lignin dan Lignin Ultrasonikasi (LU) dari TKKS mempunyai aktivitas antioksidan dan antimikroba. Lignin dan LU dari hasil isolasi dengan perlakuan H2SO4 10% (v/v) memeroleh aktivitas antioksidan tertinggi, yaitu dengan nilai IC50 masing-masing sebesar 1086,02 ppm dan 795,94 ppm. Aktivitas antimikroba tertinggi diperoleh pada lignin dari hasil isolasi dengan perlakuan H2SO4 10% (v/v), yaitu dengan diameter zona bening terhadap Bacillus subtilis sebesar 0,560 cm.
Keyword: lignin, nanolignin, antimikroba, antioksidanDPPH, tandan kosong kelapa Sawit, difusi sumur, ultrasonikasi

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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