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 Antioksidan Lignin dari Lindi Hitam Kraft Berbahan Baku Kayu Acacia mangium
Abstrak: The use of black liquor, spent liquor produced from pulp processing, can be increased through isolation and purification to produce various useful products. One of the components in the liquor is lignin. Lignin was isolated from black liquor by precipitation using H2S04 20%. Lignin has potential application as an antioxidant. Phenolic hydroxyl groups in lignin can scavenge the free radicals. In this study, antioxidant activity of lignin, which is isolated from black liquor of Acacia mangium wood as the raw material, was examined by diphenyl picrylhydrazyl (DPPH) method. Lignin would scavenge the DPPH free radicals and change the color from purple to pale yellow of diphenyl picrylhydrazine. The change of color intensity was measured by ultraviolet-visible spectrophotometer. The result showed that lignin had strong antioxidant activity with 50% inhibition concentration (IC50) value of 18 ppm, higher than 3,5-di(t-butyl)-4- hydroxytoluene with IC50 value of 1880 ppm. Antioxidant activity of lignin was increasing with the increasing phenolic hydroxyl content and the decreasing lignin molecular weight
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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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