Judul: Characterization of protoxin protein and chitinase enzyme from indigenous isolates Bacillus thuringiensis
Abstrak: Bacillus thuringiensis secreted exochitinase activity when grown in a medium containing chitin. Chitinase and protoxin protein play a important role in the pathogenicity of Bacillus thuringiensis to insect pest. This research was aimed to determined characterization of B. thuringiensis subsp. pakistani indigenous isolates, B. thuringiensis Lot II, and B. thuringiensis 47 to produce chitinase enzyme and protoxin protein. Optimum production of chitinase from B. thuringiensis subsp. pakistani was obtained at 24th hours, pH 7.5, and 40oC. B. thuringiensis Lot II was optimum at 21th hour, pH 6,0, and 50oC. B. thuringiensis 47 was optimum at 21st hour, pH 5,0, and 35 oC. Ammonium sulphate was used for precipitation of chitinase protein. The highest spesific activity of chitinase was obtained on ammonium sulphate at saturation 20% for B. thuringiensis subsp. pakistani, 30% for B. thuringiensis Lot II and 40% for B. thuringiensis 47. The highest production of protoxin protein from B. thuringiensis subsp. pakistani and B. thuringiensis 47 was obtained at 36th hour, whereas B. thuringiensis Lot II at 33rd hour. The molecule weight of chitinase molecule was determined by Sodium Dodecyl Sulfate Solution Polyacrilamide Gel Electrophoresis (SDS-PAGE). Molecular weight of chitinase of B. thuringiensis subsp. pakistani, B. thuringiensis Lot II and 47 estimated at 71,15 kDa. The weight of protoxin protein molecule all isolates estimated 129,99 and 130,04 kDa.
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Judul: Purification and characterization of thermostable chitinases from bacillus lichemiformis MB-2
Abstrak: Chitinases are of great biotechnological interest and have received remarkable attention. A themophilic bacterium, Bacillus lichenifomis MB-2, from Tompaso hot spring, North Sulawesi Indonesia, secreted thermostable chitinases into culture media. Preliminary study showed that the enzymes occur in multiple forms and were stable at a high temperature and a broad range of pH. The objectives of this research were to purify and characterize thermostable chitinases from B. lichenrformis MB-2. The extracellular chitinases were isolated by successive column chromatographies on Phenyl Sepharose CL4B, DEAE Sephacel, and Superdex G-75. The purified enzymes had molecular weight of 67 (Chi-67) and 102 kDa (Chi-102), estimated by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Chi-67 and Chi-102 had an endo- and exo- chitinolytic activities, respectively. The optimal temperature of Chi-67 was 70°C, whereas Chi-102 was 60 "C. The optimal pH for both enzymes was 6.0. Chi-67 wets stable below 60°C and over a broad pH range of 4-1 1 for 1 h. In contrast, Chi- 102 was not stable at temperature above 50 "C and only stable at its optimum pH for 1 h. Chi-47 was resistant to denaturation by urea, Tween-20 and Triton-X, but unstable toward organic solvents such as propanol, ethanol, DMSO (dimethyl sdfoxide), and PEG (polyethylene glycol), indicating that hydrophobic interaction of proteins plays an important role in maintaining enzyme activity. Ionic interactions are also important for Chi-67 fold as the activity was reduced by guanidine hydrochloride and NaCl (1 M). Chi- 1 02 was relatively more stable toward various organic solvents than Chi-67. Both enzymes hydrolyzed colloidal chitin, glycol chitin, or glycol chitosan, but were less active to regenerated chitin, fine powder of chitin, or methyl cellulose. The Michaelis constants &) for colloidal chitin, glycol chitin, 4- methylumbelliferyl N', W-diacetylchitobioside [MUF(GICNAC)~], 4- methyiumbelliferyl N', N', M-triacetylchitotrioside [MCTF(G~CNAC)f~o]r Chi-67 were 3.08 mg ml-', 0.3 15 mg ml-', 0.02 pmol d-' and 0.02 pmol dl, respectively. Meanwhile, the K, for colloidal chitin, glycol chitin and MUF(GlcNAc) for Chi-102 were 2.00 mg ml-', 1.32 rng ml-', and 0.03 mM ml-', respectively. The first 13 N-tertninal amino acids of Chi-67 were determined to be SGKNYKIIGYYPS, which is identical to chitinase from B. licImenIfomris PR- 1 (accession no. AA022 144) and B. circuImrs No. 4.1 (accession no. AM23 3 68).
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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. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular