Judul: Studi Pengaruh Alkaline Pretreatment terhadap Delignifikasi pada Lignoselulosa Gracilaria sp. (Below Standard).
Abstrak: Gracilaria sp. (below standard) merupakan biomassa berlignoselulosa yang mengandung selulosa, hemiselulosa dan lignin. Kandungan lignin menghambat konversi selulosa menjadi gula sederhana. Delignifikasi merupakan suatu proses penghilangan lignin pada material berlignoselulosa. Delignifikasi yang dilakukan pada penelitian ini yaitu mengunakan alkaline pretreatment dengan variasi konsentrasi NaOH 0, 0,01 M dan 0,05 M pada suhu 27 oC serta waktu pretreatment selama 24 jam. Komposisi lignoselulosa dari rumput laut Gracilaria sp. (below standard) sebelum pretreatment memiliki selulosa, hemiselulosa dan lignin berturut-turut 10,88%, 9,85% dan 8,76%. Pretreatment yang dilakukan pada rumput laut Gracilaria sp. (below standard) memberi pengaruh terhadap kandungan hemiselulosa, lignin dan yield regenerated biomass. Penurunan bobot lignin tertinggi (63,22%) dan jumlah yield regenerated biomass terendah 62,9% dihasikan pada perlakuan konsentrasi NaOH 0,05 M. Mikrostruktur Gracilaria sp. (below standard) setelah pretreatment mengalami kerusakan berupa jaringan yang terkoyak dan tidak kompak. Filtrat yang pada perlakuan konsentrasi NaOH 0,05 M menghasilkan gula pereduksi sebesar 98,97%
Keyword: Alkaline pretreatment, Gracilaria sp. (below standard), lignoselulosa, NaOH

Judul: Effect of Alkali Pretreatment on Enzymatic Hydrolysis in the Process of Making Bioethanol from Gracilaria sp.
Abstrak: Praperlakuan adalah proses perubahan dalam komposisi kimia, struktur makro, dan mikro dari lignoselulosa. Penelitian ini bertujuan untuk mengetahui pengaruh faktor praperlakuan dengan alkali NaOH 5% terhadap hidrolisis enzimatik pada proses pembuatan bioetanol menggunakan Gracilaria sp.sebagai bahan baku. Praperlakuan dengan alkali NaOH 5% dilakukan dengan variasi waktu yang berbeda yaitu 60, 90, dan 120 menit pada suhu 50oC. Setelah praperlakuan dilakukan proses hidrolisis enzimatis menggunakan enzim selulase pada shaker inkubator suhu 50oC, 150 rpm selama 72 jam, kemudian proses fermentasi selama 72 jam menggunakan kapang Saccaharomices cerevisiae. Hasil penelitian menunjukkan bahwa praperlakuan alkali NaOH 5% dapat meningkatkan kualitas biomassa Gracilaria sp. Kadar lignin yang dihasilkan sebesar 10,43 ± 0,15%. Hasil hidrolisis tertinggi dengan kandungan gula pereduksi sebesar 13,54 mg/ml. Uji kualitatif dengan K2Cr2O7 menunjukkan positif etanol pada larutan., Pretreatment is a process of changing the chemical composition, macrostructure, and microstructure of lignocellulose. This study aims to determine the effect of pretreatment factors with 5% NaOH alkali on enzymatic hydrolysis in the bioethanol production process using Gracilaria sp. as raw material. Pretreatment with 5% NaOH alkali was carried out with different time variations, namely 60, 90, and 120 minutes at a temperature of 50oC. After pretreatment, the enzymatic hydrolysis process was carried out using cellulose enzymes on a shaker incubator at a temperature of 50oC, 150 rpm for 72 hours, then the fermentation process for 72 hours using Saccharomices cerevisiae mold. The results showed that 5% NaOH alkali pretreatment could improve the quality of Gracilaria sp. biomass. The lignin content produced was 10.43 ± 0,15%. The highest hydrolysis resulted with a reduced sugar content of 13.54 mg/ml. Qualitative test with K2Cr2O7 showed positive ethanol in the solution.
Keyword: alkali pretreatment, enzymatic hydrolysis, Gracilaria sp., reducing sugar

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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