Judul: Pemilihan Fitur Dokumen Bahasa Indonesia untuk Pengelompokan dengan Metode K-Means
Abstrak: The field of document information retrieval has very diverse and rapidly-growing documents thereforethe need for methods to categorize documents effectively and efficiently increases. Categorizing documents can be performed using clustering techniques. This research uses the K-Means technique, one example of a partitioning clustering algorithm. K-Means is a simple algorithm that aims to get the appropriate grouping. Chi-square feature selection and the IDF were used to obtain the termsused as the unique identifiers of the documents. Clustering results with different feature selection techniques were made forcomparison to get the expected results.The accuracy values obtained for the IDF and the chi-square feature selection for data size 150 using rand index are26%, 75%, respectively.The accuracy values obtained for the IDF and the chi-square feature selection for data size 457 using rand index are31%, 37%, respectively. The accuracy values obtained for the IDF and the chi-square feature selection for data size 150 usingpurity measureare 97%, 96%, respectively. The accuracy values obtained for the IDF and the chi-square feature selection for data size 457 using rand index are 93%, 95%, respectively.
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Judul: Metode Pemilihan Fitur Dokumen Bahasa Indonesia yang Terkelompok pada Mesin Pencari
Abstrak: The large amount of information particularly in the form of large quantities of documents will required a large amount of time and effort to search if done manually. On a vector space, documents are represented by terms. More terms mean higher-dimensional data which makes search more difficult to perform. A large number of documents affects the performance of the search engine to return the documents that are relevant to the user's desires. This study implements correlation coefficient method and compareit with the chi-square method. In this study different levels of accuracy are produced. Correlation coefficient method has an accuracy of 68% while the chi-square method produced an accuracy of 58%
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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