Judul: Pemanfaatan Limbah Padat Nata de Coco untuk Produksi Bioetanol Menggunakan Zymomonas mobilis
Abstrak: Dalam proses hilir produksi nata de coco dihasilkan limbah produk berupa kulit ari, sisa potongan, dan yang tidak lolos sortasi berkisar 10% dari total produksi. Limbah tersebut mengandung selulosa yang dapat dimanfaatkan menjadi bioetanol sebagai energi alternatif. Penelitian ini bertujuan untuk mengevaluasi potensi pemanfaatan limbah nata de coco untuk produksi bioetanol. Praperlakuan bahan dilakukan dengan menghidrolisis nata de coco menggunakan enzim selulase. Proses fermentasi dilakukan dengan menggunakan Zymomonas mobilis pada suhu kamar selama 72 jam. Analisis produk dilakukan setiap 12 jam. Dalam penelitian ini dievaluasi pengaruh tingkat penggunaan konsentrasi inokulum Zymomonas mobilis, yaitu 10% dan 15% (v/v) dan pengaruh penambahan urea sebagai nutrisi. Hidrolisis dengan enzim selulase sebesar 30IU/g serat kasar menghasilkan hidrolisat sebesar 1.77 L/kg bahan dan meningkatkan gula pereduksi 0.08 g/L menjadi 6.8 g/L. Pemakaian 15% inokulum menghasilkan kadar etanol yang lebih tinggi yaitu 0.27% (v/v) dibandingkan dengan 10% inokulum yaitu 0.2% (v/v). Penambahan urea sebesar 2.9 g/L substrat meningkatkan kadar etanol dari 0.2% menjadi 0.25% pada tingkat 10% inokulum dan dari 0.27% menjadi 0.3% pada tingkat 15%. Kadar etanol tertinggi dihasilkan oleh inokulum 15% (v/v) dengan penambahan nutrisi dan yield (p/s) yang dihasilkan adalah 0.49±0.02 (g/g). Waktu optimum fermentasi adalah 48 jam dan kadar gula tersisa 22.4±0.8%. Hasil analisis kelayakan finansial menunjukkan nilai R-C ratio sebesar 0.3.
Keyword: bioetanol, energi, enzim selulase, hidrolisis, limbah padat nata de coco, R-C ratio

Judul: Produksi Bioetanol dari Limbah Tanaman Jagung Melalui Sakarifikasi dan Fermentasi Simultan Menggunakan Biakan Zymomonas mobilis dan Pichia stipitis
Abstrak: Bioethanol is renewable energy can produce from fermentation of sugar (Anuj et al., 2007). Bioethanol can be given from material that has lignocellulose. Indonesia has a pottential raw material that can be renewable. In Indonesia this material is plenitude and have a high componnent cellulose inside. The use of harvest stover has advantages there are not have competitive with food, price is cheap, and that material is so much in Indonesia (Rachamniah et al., 2009). Usually, cornstover only can be used to fuel (dirrect), feedstock, and most of not use and only be waste. This waste have a component such as cellulose 36.81%, hemicellulose 27.01%, lignin 15.07% and ash 6.04%. (Anonim, 2009). Use of Lignococellulotic only a part of cellulose, whreas 27.01% ingredients of cornstover is hemicellulose can be used to ethanol production. Use of hemicellulose hoped can increase concentration of ethanol. Hydrolysis process and fermentation will be effective and efficient if done continiusly without long time break or use simultaneous saccharification and fermentation process (SSF). In tis process use enzym cellulase, xylanase, β-glucosidase added for produce glucose and xylose. Microorganism that can used for produce ethanol such as Zymomonas mobilis and Pichia stipitis. Zymomonas mobilis can produce ethanol (5-10%) and productivity (2,5 times) higher than Saccharomyces cereviseae (Zhang et al., 1995 and Dien et al., 2003). Pichia stipitis can use pentose that can not use by Saccharomyces cererviseae and Pichia stipitis. The objectives of this research are to determine productivity of saccharification and fermentation process with measuring fermentation parameters, such as producing biomass, changing of pH, using of reduction sugar, using of total sugar, producing ethanol, the correlation of substrate consumption to the product or biomass, biomass to the product and efficiency for each microorganism. In this research, pretreatment process there are delignification, hydrothermal I and hydrothermal II. Delignification using 0,073 g/g cornstover. Condition temperature of delignification that is 74,6oC as long as 2 hour (Hakim, 2010). Condition temperature of hydrothermal I that is 121oC as long as 1 hour. Condition temperature of hydrothermal II that is 180oC as long as 20 minute. After that, cornstover that has pretreatment 6,67% (dw/v) mix with liquor substrate. Liquor substrate consist of liquor from pretreatment and buffer sitrate phosphate pH 5 with comparison 1:1. After that, hydrolysis enzym process done with added cellulase 7 IU/g cellulose and xylanse 3 IU/g hemicellulose. Condition temperature of hydrolysis enzym that is 50oC as long as 24 hour. After process hydrolysis enzim finished, simultaneous saccharification and fermentation done with the temperature condition that is 32oC, added nutrient fermentation that is urea (24%) has many 0,167% (v/v) (Thomsen et al., 2008). Hydrolysis enzym process done with added cellulase 7 IU/g cellulose, xylanse 3 IU/g hemicellulose, and β-glucosidase added has many 1 IU/g cellulose. The starter added that is 10% (v/v) (Samsuri et al., 2007). Starter that use from microorganism Zymomonas mobilis, mix of microorganism Zymomonas mobilis and Pichia stipitis and Pichia stipitis As long as simultaneous saccharification and fermentation going on, measuring done such as biomass, pH, reduction sugar and total sugar analysis.
Keyword: 

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
Keyword: