Judul: Ultrasonic Pretreatment of Gracilaria sp. Processing in  Bioethanol Manufacturing
Abstrak: Bioetanol terbuat dari bahan berselulosa melalui beberapa tahapan proses. Rumput laut Gracilaria sp. memiliki potensi sebagai bahan baku bioetanol karena mengandung selulosa. Praperlakuan ultrasonikasi dengan larutan alkali dalam pembuatan bioetanol menarik untuk dilakukan karena mampu meningkatkan rendemen etanol. Penelitian ini bertujuan untuk menentukan pengaruh waktu praperlakuan ultrasonikasi dengan larutan alkali pada bahan baku untuk meningkatkan kandungan total gula pereduksi dan kadar etanol. Tahapan penelitian meliputi persiapan sampel, praperlakuan ultrasonikasi dalam alkali dengan waktu 60, 90 dan 120 menit, sakarifikasi, fermentasi dan destilasi. Selulosa teridentifikasi pada sampel ditandai dengan adanya puncak pada bilangan gelombang 1058 cm-1 . Praperlakuan ultrasonikasi 120 menit menghasilkan kandungan total gula pereduksi dan kadar etanol tertinggi masing-masing sebesar 96,34 mg/mL dan 3%., Bioethanol is made from cellulosic materials through several stages of the process. Seaweed of Gracilaria sp. has potential as raw material for bioethanol since it contains high cellulose. The pretreatment of ultrasonication with alkaline solutions in bioethanol production is interesting because it can increase the yield of ethanol. This study aims to determine the effect pretreatment time of ultrasonication with alkaline solutions in increasing the total content of reducing sugars and ethanol yield. The research includes sample preparation, pretreatment of ultrasonication in alkaline at times 60, 90 and 120 min, saccharification, fermentation and distillation. Cellulose is identified in the functional group analysis characterized by a peak at wave number 1058 cm-1 . The pretreatment of 120 min ultrasonication resulted in the highest total content of reducing sugar and ethanol content of 96.34 mg/mL and 3% respectively.
Keyword: alkaline, bioethanol, Gracilaria sp, ultrasonication

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: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model