Judul: Suatu studi mengenai pembandingan sistim struktur kuda papan paku dan konvensional untuk atap rumah
Abstrak: Tujuan penelitian ini adalah untuk mengetahui sampai seberapa jauh tingkat efisiensi sistim struktur kuda kuda papan paku, baik segi struktur maupun pemakaian bahannya, dibandingkan sistim konvensional. Dua macam tipe sistin kuda kuda konvensionil dan empat macam tipe sistim kuda- kuda papan paku dianalisa dalam penelitian ini dengan meng gunakan metoda "The Displacement Method of Truss Analysis".
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Judul: Rancangan kuda-kuda papan tipe mansard untuk kandang sapi perah
Abstrak: Tujuan penelitian ini adalah untuk mempelajari kekuatan rancangan kuda-kuda papan tipe mansard dan kekuatan sambungan yang menggunakan alat sambung paku, perekat dan gabungan dari paku dan perekat. Pemilihan tipe ini ditujukan untuk memperoleh ruangan yang cukup luas di bawah atap, dan digunakan sebagai tempat menyimpan persediaan pakan. Pengujian rancangan dilakukan terhadap model dengan pemberian beban vertikal. Model bersifat sama secara geometri (geomtrically similar). Sedang kekuatan sambungan diuji dengan pemberian beban tarik sejajar serat. Berdasarkan perhitungan, beban rencana rancangan kuda- kuda sebesar 1650 kg, dengan faktor keamanan 2,5 sehingga besar beban rencana model adalah 45,83 kg. Skala linier model N = 6. Dari pengujian, beban ijin model dengan alat sambung paku adalah 81,574 kg, sehingga beban ijin untuk rancangan kuda-kuda adalah 3000 kg. Oleh karena itu beban rencana (Pd) rancangan kuda-kuda papan diambil dari rata- ratanya, yaitu 2325 kg. Sambungan pada kuda-kuda papan cukup kuat menyalurkan tegangan yang ada. Hal ini terlihat dari jenis kerusakan yang terjadi pada saat pengujian yaitu patah pada batang kritis, sedangkan sambungan tetap dalam kondisi baik. Pada tingkat kepercayaan 95 persen, ketiga ukuran pelat sambung memberikan pengaruh yang nyata terhadap keku- atan sambungan paku. Sedang pada sambungan perekat dan gabungan dari paku dan perekat tidak memberikan perbedaan yang nyata. Sambungan paku mempunyai kekuatan terkecil, dibanding dengan sambungan perekat dan gabungan keduanya. Penggunaan ketiga macam alat sambung pada tiap-tiap ukuran pelat sambung, masing-masing menunjukkan adanya perbedaan pengaruh yang nyata terhadap kekuatan sambungan…dst
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Judul: Extracellular Expression of thermostable Geobacillus stearothermophilus T1.2RQ Lipase for Biodiesel Production
Abstrak: The extracellular expression of enzymes in an excellent secretion host such as Bacillus subtilis is a useful strategy for making enzymes of industrial significance more affordable by lowering the cost of its downstream processing. Lipases are a category of hydrolases that catalyze the hydrolysis of triglycerides to glycerol and free fatty acids. Also, lipases catalyze the hydrolysis and transesterification of other esters as well as the synthesis of esters. They can perform very specific biotransformation reactions and are widely used in food, organic synthesis, detergents, cosmetic, and pharmaceutical industries. Geobacillus stearothermophilus T1.2RQ lipase is an industrially-desired thermostable lipolytic enzyme with an excellent hydrolytic and transesterification activity. This study aimed to express T1.2RQ lipase, in B. subtilis WB800 and ensure its secretion into the extracellular medium. Three signal peptides (AmyQ, Epr, LipA) and two promoters (Pgrac01 and Pgrac100) were used in the secretory-expression of T1.2RQ lipase, based on five constructed expression vectors constructed by restriction cloning and PCR mutagenesis. Sangers sequencing was used to verify constructs to ensure they are in the correct reading frame. Recombinants vectors, pHT43 (plasmid control), pHT43-T1.2RQ, pHT43- T1.2RQ_AmyQ, pHT43-T1.2RQ_Epr, and pHT43-T1.2RQ_LipA, were transformed by electroporation into Bacillus subtilis WB800. The electroporation was successful with the optimum condition of 2500V, 200 ohms, 25µF, and 5milliseconds. Recombinant B. subtilis pHT43 (negative control) and pHT43-T1.2RQlip + signal peptides were streaked on the lipidic agar, LA+TBN. All four recombinants, including the negative control (B. subtilis WB800-pHT43), produced clear zones on the TBN agar plate after overnight incubation (fig 2), indicating the presence of a lipolytic enzyme in all of the recombinant B. subtilis cells. pHT43-T1.2RQlip + signal peptides (AmyQ, Epr, and LipA) have clear zones with significantly higher diameters than B. subtilis WB800-pHT43 (negative control). This phenomenon suggests that the recombinant thermostable lipase T1.2RQ introduced into these cells was successfully expressed, thereby increasing the lipolytic capability of its host cells T1.2RQ lipase was expressed in 50ml terrific broth medium (TB) and the expression induced with 1mM IPTG. Lipase activity assay using p-nitrophenyl esters showed that all three signal peptides directed the secretion of T1.2RQ lipase into the extracellular medium. Signal peptide, LipA, resulted in the highest extracellular activity of 5.6 U/mL, which corresponds to a 6-fold increase over the parent B. subtilis WB800 strain. Meanwhile, signal peptides, AmyQ and Epr produced 4.2 U/mL and 3.4 U/mL activity respectively. SDS-Zymogram analysis confirmed that T1.2RQ lipase was correctly processed and secreted in its original size of 44 kDa. An attempt to further increase lipase expression level by promoter optimization showed that, contrary to expectation, promoter Pgrac100 exhibited similar expression levels as the original Pgrac01. Nevertheless, the demonstration of the successful secretion of T1.2RQ lipase in this work confirms the latter as a promising approach for the industrial production of the enzyme
Keyword: Bacillus subtilis, Expression, Extracellular, Heterologous, Lipase, Thermostable