Judul: Selection of actinomycetes for degradation lignocellulosic biomass.
Abstrak: Lignocellulose is the major structural component of woody plants and nonwoody plants which represents a major source of renewable organic matter. The structural component lignocelluloses consist of 40% to 50% cellulose, 20% to 30% hemicellulose, 10% to 25% lignin and extractable components. The component of lignocellulose biomass can potentially be converted into various different valuable products including biofuels, organic chemicals, cheap energy sources for fermentation, and improving animal feeds and human nutrients. Lignocellulose components are difficult to hydrolyze because cellulose is associated with hemicellulose, their fiber surrounded by a lignin seal and much of it has a crystalline structure, giving it a highly ordered, tightly packed structure. Delignification should be done for increasing the surface area of cellulose by removing the lignin seal, solubilizing hemicellulose, disrupting crystallinity, and increasing pore volume. This study aims to obtain isolates of actinomycetes that produce lignin peroxidase enzyme and applied it for delignification agricultural biomass such as sugarcane bagasse, corn cobs, oil palm empty fruit bunch (OPEFB), and sawdust. The study was conducted into three main steps as the following: selection of actinomycet isolate that produce lignin peroxidase, characterization of selected isolate, and applied it for delignification agricultural biomass. Qualitative observations using congo red and fuchsin were conducted as the initial screening. Screening by congo red revealed 11 isolates that produce clear zone, while only one isolate (isolate 42) obtained Fuchsin screening. This isolate secreted lignin peroxidase enzymes with the highest activities after 8 days as 24.46 U/mg, and xylanase enzyme after 10 days as 0.055 U/ml. Actinomycetes isolate 42 can grow on all lignocelullose substrates, and degraded all components in the substrates. After 6 weeks cultivation, degradation caused 2.14-13.8% lossed weight, with the highest weight loss from sugar cane substrate. Isolate 42 has highest delignification capability (7.45%) and cellulose degradation (10.69%) on corncobs and, highest hemicelullose solubilization capability on OPEFB (9.93%)
Keyword: Actinomycetes, delignification, lignin peroxidase activity, lignocellulosic biomass, Streptomyces sp.

Judul: Karakterisasi Enzim Selulase dan Aplikasinya pada Substrat Limbah Pertanian
Abstrak: Cellulose is the most abundant plant cell walls. Lignocellulolytic are consist of cellulose, hemicelluloses and lignin. Degradation of cellulose involves a complex interplay between different cellulolytic enzymes. Among others, it has been widely accepted that three types of cellulases including endoglucanases, exoglucanases and β-glucosidases act synergistically to convert cellulose to glucose. This study was aimed to characterized cellulase enzyme which produced by cellulolytic bacteria from soil and applied it on agricultural waste such as rice straw, corn cob and banana peel. Qualitative analysis have done on 9 isolates cellulolytic bacteria to know the highest cellulolytic index by using congo red 0.1%. From 9 isolates, 1 isolate have IS 1.75. Quantitative analysis showed isolate 6-2 has the highest cellulase activity of 0.005U/ml. Highest activity of cellulase enzyme from isolate 6-2 resulted on bufer pH 7 and 40oC. Cellulase activity of isolate 6-2 was stable for 75 minutes. Isolate 6-2 has relatively low cellulase activities in CMC as it has small enzyme activity in degrading substrates of agriculture waste. The cellulose enzyme activity on ricestraw resulted 0.007U/ml, corncob resulted 0.008U/ml, and bananapeel resulted 0.013U/ml. Isolate 6-2, gram positive bacteria can degrade cellulose by using cellulase enzyme. On the application cellulase enzyme activity on bananapeel was higher than the others.
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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