Judul: The utilization of sawdust for ethanol production
Abstrak: Currently, Indonesia is in the middle of petroleum crisis. One of the alternative fuels which can be used as a petroleum substitute is ethanol. Ethanol can be produced from the timber waste (sawdust). Indonesia, in 2003, had timber waste potency of about 3 – 4 millions m3. Process of sawdust manufacturing become an ethanol can be conducted by simultaneous saccharificationfermentation method. However, ethanol production from sawdust has problem due to its lignin content. Therefore, research on bio-delignification treatment of sawdust prior to ethanol making process is required. The research was done by acted of growing white rot fungi Phanerochaete chrysosporium on three kinds of sawdust i.e. jati, meranti and sengon. The chemical contents (extractive contents, cellulose contents, holocellulose contents, ash contents and lignin contents) of these three of sawdust were analyzed previously. Then simultaneous saccharification-fermentation (SSF) process was done by using crude enzyme from Trichoderma viride and then followed by fermentation with Saccharomyces cerevisiae on shaker incubator with rate 12 rpm at temperature 30oC for 72 hours. The result as an ethanol was analyzed by using gas chromatography method. Analysis design used was completely randomized design using 2 factors of treatment i.e. type of wood (A) and time of incubation (B). Pretreatment with Phanerochaete chrysosporium on various types of sawdust and incubation time rises up ethanol contents up to about 26.68 – 76.90%. Chemical contents of sawdust having significant effect to ethanol contents was holocellulose, the higher holocellulose contents give higher ethanol contents. Ethanol contents resulted was about o.o16 – 0.448 g/l. Interaction between factor type of wood and time of incubation had significant effect to ethanol content. The best combination treatment was on sengon sawdust with incubation period of 30 days.
Keyword: 

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: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf