Judul: Komunitas Aktinobakteri Endofit Tabat Barito (Ficus deltoidea) Berdasarkan Pendekatan Kultivasi dan Metagenomik
Abstrak: Aktinobakteri endofit pada tanaman obat berperan penting dalam menghasilkan berbagai macam senyawa bioaktif. Tabat barito (Ficus deltoidea) telah lama digunakan untuk mengobati beberapa penyakit. Namun, keragaman dan kemampuan aktinobakteri endofit tabat barito belum pernah dieksplorasi sebelumnya. Informasi tentang eksistensi komunitas aktinobakteri endofit pada tabat barito dapat dijadikan dasar untuk mengeksplorasi potensinya lebih lanjut. Struktur komunitas aktinobakteri endofit tabat barito dapat diketahui dengan menggunakan pendekatan kultivasi dan metagenomik. Berdasarkan karakteristik morfologi dan melalui analisis gen 16S rRNA, aktinobakteri endofit terkultivasi memiliki kesamaan dengan genus Streptomyces sebagai genus yang dominan. Teknik metagenomik menggunakan PCR-DGGE berdasarkan gen 16S rRNA menunjukkan keragaman aktinobakteri yang lebih tinggi dibandingkan teknik kultivasi. Berdasarkan teknik PCR-DGGE terdapat enam genus aktinobakteri berbeda yang tersebar pada jaringan tanaman tabat barito yaitu Streptomyces, Intrasporangium, Actinomadura, Verrucosispora, Kineospora, dan Rhodococcus. Berdasarkan kajian ini dapat diketahui bahwa aktinobakteri endofit tabat barito yang terkultivasi didominasi oleh Streptomyces berbeda dengan hasil pendekatan metagenomik. Pendekatan metagenomik berdasarkan nilai OTU menunjukkan bahwa Rhodococcus merupakan genus yang paling dominan pada jaringan tabat barito, sedangkan Streptomyces merupakan genus kedua tertinggi setelah Rhodococcus. Observasi dari kedua pendekatan kultivasi dan metagenomik memberikan pemahaman yang lebih baik tentang keragaman dan struktur komunitas aktinobakteri endofit tabat barito.
Keyword: Aktinobakteri, Endofit, Tabat Barito, Metagenomik, PCR-DGGE

Judul: Potensi Aktinobakteri Endofit Tabat Barito ('Ficus deltoidea Jack) sebagai Penghasil Inhibitor a-Glukosidase
Abstrak: Diabetes mellitus (DM) is a chronic and serious metabolic disorder that is t revalent in the world. Diabetes mellitus occurs due to insulin deficiency and inswli resistance. This condition causes high blood glucose levels or called hYN.. rglycemia condition. One therapeutic approach to treat diabetes is to retard the abs" tion of glucose via inhibition of enzymes, such as a-glucosidase, in the small tinal. Inhibition of this enzyme slows the elevation of blood glucose following · rl:hohydrate meal. The a-glucosidase inhibitor is a bioactive compounds i8uted widely in plants and microorganisms including actino bacteria. }\ctinobacteria are Gram positive bacteria widely distributed in nature. They produce numerous metabolic products, most of which are bioactive compound with applications in many therapeutic areas. Actinobacteria are predominantly free living and are found in diverse environments including plants tissue. Microbes that live on plant tissues without causing harmfull to the host are called endophytes. Such icrobial endophytes are beginning to pay attention ofresearchers due to their abilit)1 to produce various compounds of pharmacological value similar to their li.osts. Previous reports showed that endophytic actinobacteria have a-glucosidase mhibi or activity such as Tinospora crispa (Brotowali) and Datura stramonim L (Kecubung). lf abat barito (Ficus deltoidea Jack) is a medicinal plant originating from Southeast Asia. In Indonesia, tabat barito has the most distribution in Borneo island. Tabat barito was used traditionally to treat diabetes. On another hand, several studies have shown that tabat barito has an a-glucosidase inhibitor activity. The abilit)1of tabat barito to produce a-glucosidase inhibitors is suggested to be related to the presence of endophytic microbes including actinobacteria. Previous studies showed that the abundance of actinobacteria in the tabat barito plant tissue is quite umer:ous and varied. Based on these reports, it is expected that the capability of abat barito on producing a-glucosidase inhibitors is related to the presence of actinobacteria. In this study, it was proven that endophytic actinobacteria from tabat barito <t:ould produce a-glucosidase inhibitors. Screening using a-glucosidase from rat intestine is recommended for in vitro a-glucosidase inhibitor because the homology sequeroce of catalytic side closer to enzymes in the human intestine. In this study endophytic actinobacterial isolates more inhibited a-glucosidase from rat intestines according to acarbose which only inhibit mammalian a-glucosidase. Screening of 40 enoophytic actinobacteria isolates using yeast a-glucosidase showed that 25 sG).}ates (62%) of isolates had a-glucosidase inhibitors activity. Whereas screening msm rat intestinal enzymes from 40 isolates, 31 isolates (77%) had a-glucosidase lnor activity. Aqueous extract and n-hexane ofTBL 7 isolates were the best extracts for a­ sidase inhibition, IC₅₀ value of 159.25 µg mL-¹ (aqueous extract) and 118.52 mIL-1 (n-hexane extract). Based on the 16S rRNA gene TBL 7 showed was similar to Streptomyces tendae (99.91%). The ISP 2 medium with 10 days incubation period is the best condition to produce a-glucosidase inhibitor compound. After fractionation, AF 2 from aqueous crude extract has ICso value of 58.8 µg mL-I, higher than acarbose as positive control (ICso = 90.4 µg mL-I). The LC-MS analysis showed that the fraction of AF 2 had bioactive compounds similar t phenylpropynal, butyric acid, solketal, p-coumaric
Keyword: Actinobacteria, Diabetes mellitus, Endophytes, Tabat barito

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
Keyword: