Judul: Kajian Sensitivitas Parameter Algoritme Pada Metode Rotation Forest
Abstrak: Rotation forest merupakan metode klasifikasi baru untuk membangun metode pohon gabungan (classifier ensembles) dengan menggunakan pohon keputusan yang saling bebas. Proses pembeda dalam rotation forest adalah penerapan analisis komponen utama untuk merotasi peubah asal menjadi peubah baru yang saling bebas. Beberapa penelitian telah membuktikan bahwa rotation forest lebih akurat dalam melakukan dugaan klasifikasi dibandingkan metode bagging dan random forest. Penentuan parameter algoritme, yakni ukuran banyaknya pohon keputusan yang digunakan dalam metode gabungan (l) dan banyaknya pemisah gugus peubah asal (k) memegang peranan penting dalam menentukan keberhasilan dan keakuratan dugaan klasifikasi. Penelitian ini menggunakan data dengan peubah respon terdiri dari 2 kategori/kelas. Hasil penelitian adalah: (1) Tidak didapatkan nilai k spesifik untuk tiap kategori data yang dapat memaksimumkan nilai keakuratan klasifikasi nilai, nilai k = (p-1) cenderung menghasilkan keakuratan klasifikasi yang lebih rendah dibandingkan nilai k = {1, 2, 3, p/3}. (2) Metode gabungan rotation forest efektif digunakan untuk melakukan pengklasifikasian data dengan hanya menggunakan sedikit pohon keputusan yakni 10 sampai 20 pohon. (3) Terdapat hubungan negatif antara nilai keakuratan klasifikasi dengan proporsi keragaman kumulatif data, yakni semakin tinggi nilai proporsi keragaman kumulatif suatu data cenderung menurunkan nilai keakuratan klasifikasi, atau sebaliknya.
Keyword: analisis komponen utama, metode pohon gabungan, rotation forest

Judul: Kajian empirik kinerja metode klasifikasi biner Rotation Forest pada data tidak seimbang
Abstrak: Pemodelan klasifikasi biner dengan metode pohon gabungan rotation forest merupakan salah satu solusi untuk klasifikasi yang lebih akurat yang dapat dikembangkan. Penelitian ini mengukur kinerja metode klasifikasi biner rotation forest secara empirik pada data tidak seimbang, menggunakan data penumpang pada peristiwa tenggelamnya kapal Titanic tahun 1912. Metode ini bekerja cukup baik jika kelas dari variabel respons seimbang. Metode ini juga masih cukup baik ketika Imbalanced Ratio (IR) kurang dari 5.67 atau proporsi kelas minoritas lebih besar dari 15%. Pada kasus data dengan proporsi kelas positif atau minoritas 5%, rotation forest gagal menghasilkan kinerja klasifikasi yang lebih baik dibandingkan dengan random forest.
Keyword: binary classification, ensemble tree, imbalanced data, rotation forest

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