Judul: Heterologous Expression Of Endo-Β-Xylanase From Bacillus Pumilus Strain Bcrs-01 In Escherichia Coli.
Abstrak: Xylanases are glycoside hydrolase family 11 which depolymerise xylan in the plant cell wall, the most excessive form of hemicellulose. Endo-β-xylanases (EC 3.2.1.8) are most important to breakdown β-1,4-glicoside bond of xylan to produce disaccaride xyloolygosaccaride (XOs) and xylose (monomer). Bovine rumen fluids have potential to obtain endo-β-xylanase produced of bacteria. The objectives of this study were to obtain xylanase producing bacteria and to express xynA gene encoding endo-β-xylanase from bacterium in Escherichia coli. Twenty nine isolate bacteria have been succesfully isolated from bovine rumen fluid in agar medium containing birchwood xylan. Isolate BCRS-01 bacterium was previously screened for the high production of xylanase. Based on 16S rRNA gene sequence analysis, BCRS-01 showed high similarity (99%) to Bacillus pumilus (accession number NR043241). The crude xylanase had optimal activity at 55oC, pH 7.0. Furthermore, the crude xylanase exhibited broad pH stability from 4.0 to 10.0 and remained more than 60% and 40% of its activity after incubation at pH 4.0 until 10.0, respectively for 60 min. It also showed a stability at temperature 25-50oC since it retained 80% and 50% of its activity when incubated at 50oC or 30 and 60 min, respectively. The xylanase activity was strongly inhibited by Ca2+ and Cu2+ at concentration 10 mM, and as little as 1 mM for Mn2+. Therefore, this xylanase has potentially used as additive feeds in animal feed industry. The DNA sequence xynA gene encoded endo-β-xylanase was amplified and cloned into the expression vector pET-15by under the control of T7 promoter. The recombinant protein had succesfully expressed in Escherichia coli BL21 (DE3) pLysS. A protein recombinant of approximately, 26.7 kDa was observed on the SDS-PAGE analysis. Crude extract of recombinant endo-β-xylanase demonstrated activity of enzyme at 56 U mL-1 using birchwood xylan as a substrate at 55oC for 10 min.
Keyword: Bacillus pumilus, bovine rumen fluid, endo-β-xylanase, heterologous expression.

Judul: Kloning Gen Xilanase Termozim Dari Streptomyces costaricanus 45I-3
Abstrak: Biopolymer xylan has a great potential to produce useful end product such as xylose. Xylanases is a group of enzyme that has ability to hydrolyse xylan or polymer of xyloses and xylooligosaccharides. Complete hydrolysis of xylans involves the synergistic action of a xylanolytic enzymes, including ß-xylanase, ß-xylosidase, -glucuronidase, -L-arabinofuranosidase, and acetyl xylan esterase. The aims of this research were to isolate xylanase gene from Streptomyces costaricanus 45I-3 and to clone this gene into competence Escherichia coli DH5 . Genomic DNA was obtained from S. costaricanus 45I-3 that have known has ability to produce thermostabile extracellular xylanase. Genomic DNA was partially digested with restriction enzyme Sau3A1. Genomic DNA fragments of size 4-10 kb were inserted at BamHI site in pBluescript II KS (+) vector and transformed into E. coli DH5 . Based on blue-white selection approximately 12000 recombinant colonies were obtained. The presence of xylanase gene was identified by screening employing congored plate clearance assay. One positive clone containing the xylanase gene was confirmed and was designated as pHS11. Preliminary characterization of pHS11 using EcoRI showed that it contained a 6,0 kb DNA insert. Xylanase were produced has xylanase spesific activity 6,393 U/mg, -xylosidase activity 0,208 U/ml, arabinofuranosidase activity 0,079 U/ml and acetyl xylan esterase activity 0,063 U/ml as well.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.