Judul: Karakteristik morfometrik daerah aliran sungai dan hubungannya dengan debit sedimen suspensi : studi kasus daerah aliran sungai Cimanuk Hulu, Jawa Barat
Abstrak: Masalah yang sering dihadapi dalam perencanaan DAS adalah tidak tersedianya data, atau kalaupun ada hanya dalam waktu pencatatan yang singkat saja. Beberapa penelitian telah dilakukan untuk melihat hubungan dan memperkirakan sifat-sifat aliran dengan menggunakan karakteristik-karakteristik DAS yang secara relatif lebih mudah diperoleh. Penelitian ini dilaksanakan dengan tujuan untuk melihat hubungan antara beberapa karakteristik morfometrik DAS dengan sifat aliran, dalam hal ini debit sedimen suspensi. Sebagai daerah penelitian dipilih DAS Cimanuk Hulu, karena diperhitungkan daerah ini memiliki data yang cukup memadai. Karakteristik morfometrik DAS yang diteliti diperoleh melalui pengukuran pada peta, meliputi: luas DAS, kerapatan drainase, konstanta pemeliharaan saluran, frekuensi segmen, panjang saluran utama, panjang DAS, panjang aliran limpasan, lebar DAS, rasio elongasi, rasio sirkularitas, rasio bentuk DAS, rasio kekasaran, ras relief, relief maksimum, kemiringan saluran utama dan ketinggian rata-rata DAS. Curah hujan tahunan diperoleh dari beberapa stasiun pengukuran, sedangkan luas hutan dan luas sawah diperoleh dari pengukuran pada peta tata guna lahan.
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Judul: Pengaruh karakteristik daerah aliran sungai terhadap aliran permukaan di Sub DAS Cimanuk Hulu Jawa Barat
Abstrak: Penelitian ini bertujuan untuk mengetahui parameter- parameter karakteristik DAS, mengetahui pengaruh curah hujan terhadap aliran permukaan serta mengkaji sejauh mana pengaruh perubahan penggunaan lahan terhadap aliran permu- kaan yang terjadi di DAS tersebut. Bentuk DAS Cimanuk hulu cenderung melebar, ditunjuk- kan dengan nilai koefisien bentuk (F) 0,468; lebar rata- rata DAS (W) 15,037 km; dan nisbah sirkularitas (Rc) 0,4849. Keadaan DAS Cimanuk Hulu juga cenderung datar ditunjukkan oleh nilai kerapatan sungai (Dd) 1,061 km-1; kemiringan rata-rata 3,36%; faktor topografi (T) 169,741 km; dan kekasaran DAS 1,108. Aliran permukaan yang terja- di juga cepat, ditunjukkan oleh nilai nisbah percabangan (Rb) 3,822 dan panjang aliran limpasan (Lg) 0,471 km. Hasil analisa curah hujan wilayah bulanan di DAS Ci- manuk Hulu dari tahun 1978-1987, menurut Schmidt dan Ferguson tipe hujannya termasuk tipe B. Hubungan antara curah hujan dengan debit aliran langsung berdasarkan analisa regresi pada periode 1975- 1977 diperoleh persamaan Y 9,436 2,213X dengan nilai = 0,937, sedangkan periode 1989-1991 diperoleh persa- = 2,133 5,703X dengan nilai (r) = 0,850. Berda- (r) maan Y sarkan analisa keragaman, pada kedua periode menunjukkan taraf sangat nyata pada tingkat kepercayaan 99%, berarti curah hujan sangat mempengaruhi aliran permukaan....
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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