Judul: Screening of Actinomycetes Producing Endo-β-1,3-Glucanase Enzymes from The Maize Rhizosphere and Detection of The Encoding Genes
Abstrak: Aktinomiset rizosfer merupakan salah satu mikroorganisme yang berpotensi sebagai agen biokontrol terhadap cendawan fitopatogen, salah satunya melalui produksi enzim mikolitik seperti glukanase. 11 isolat aktinomiset telah berhasil diisolasi dari rizosfer jagung, dan telah diketahui memiliki aktivitas pemacu pertumbuhan dan biokontrol antifungi, namun belum diketahui potensinya dalam menghasilkan glukanase. Penelitian ini bertujuan untuk menyeleksi aktinomiset rizosfer jagung penghasil glukanase dan mendeteksi keberadaan gen endo-β-1,3-glukanase. Berdasarkan uji kualitatif pada medium yang mengandung 0,5% beta glukan, seluruh isolat mampu menghasilkan enzim glukanase yang beragam yaitu berkisar antara 1,63±0,18 - 2,00±0,24. Tiga isolat dengan indeks glukanolitik tertinggi yaitu ARJ 32 (2,00±0,24), ARJ 38 (1,97±0,12), dan ARJ 23 (1,88±0,14). Amplifikasi PCR menggunakan primer Bgl16F dan Bgl16R menunjukkan bahwa seluruh isolat memiliki gen endo-β-1,3-glukanase dengan pita berukuran ± 160 pb. Analisis lebih lanjut diperlukan untuk menentukan potensinya sebagai agen biokontrol terhadap cendawan fitopatogen., Rhizosphere actinomycetes are one of the microorganisms that have the potential as biocontrol agents against phytopathogenic fungi by producing mycolityc enzymes such as glucanase. A total of 11 isolates of maize rhizosphere actinomycetes were used in this study. Previously, these isolates have been studied to have potential in promoting plant growth and in inhibiting fungal growth, but their potential in producing glucanase is not studied yet. Based on the qualitative test on the medium containing 0.5% β-glucan, all isolates were able to produce the glucanase enzyme with various glucanolytic indexes ranging from 1,63±0,18 to 2,00±0,24 three highest indexes showed by ARJ 32 (2.00±0.24), ARJ 38 (1.97±0.12), and ARJ 23 (1.88±0.14). In addition, all isolates have been detected to have gene encoding glucanase with amplicon size ± 160 bp, as amplified by using Bgl16F and Bgl16R primers. In conclusion, this study showed these isolates attributed with glucanase activity are potential to be further developed as biocontrol candidates.
Keyword: Aktinomiset, β-1,3-glukanase, PCR, penapisan

Judul: Production of ß-1,3-Glucanase Enzyme from  Streptomyces sp. Antifungal Phytopathogens on Several Mediums and  Determination of its Activity
Abstrak: Enzim ß-1,3-glukanase merupakan enzim hidrolitik yang mampu mendegradasi ß-glukan penyusun dinding sel cendawan fitopatogen. Enzim ini dapat diproduksi Streptomyces tritolerans ARJ 32 dan Streptomyces collinus ARJ 38 dan berpotensi sebagai fungisida alami. Namun, produksi enzim ini membutuhkan media produksi yang relatif mahal. Oleh karena itu, penelitian ini bertujuan memproduksi enzim ß-1,3-glukanase dari S. tritolerans ARJ 32 dan S. colinus ARJ 38 antifungi fitopatogen pada beberapa medium dan menentukan aktivitasnya. Kuantifikasi aktivitas enzim ß-1,3-glukanase menunjukan nilai aktivitas tertinggi kedua Streptomyces sp. yang dikulturkan di media ekstrak ubi jalar, yakni sebesar 32,970 U/mg (S. tritolerans ARJ 32) dan 80,410 U/mg (S. collinus ARJ 38). Nilai aktivitas enzim ß-1,3-glukanase ini menunjukkan bahwa ekstrak ubi jalar berpotensi digunakan sebagai media alternatif produksi enzim ß-1,3-glukanase. Streptomyces sp. memiliki aktivitas antifungi terhadap F. oxysporum dan R. solani dengan penghambatan 23,96% dan 32,52% (ARJ 32) dan 21,88% dan 37,40% (ARJ 38)., ß-1,3-Glucanase enzyme is a hydrolytic enzyme capable of degrading ß-glucan constituting fungi cell wall. This enzyme can be produced by Streptomyces tritolerans ARJ 32 and Streptomyces collinus ARJ 38 and has potential as a natural fungicide. However, the production of this enzyme requires relatively expensive ingredients. Therefore, this study aimed to produce ß-1,3-glucanase enzymes from S. tritolerans ARJ 32 and S. colinus ARJ 38 against phytopathogenic fungi on several media and determining their activity. Quantification of glucanase enzyme activity showed the highest activity of both Streptomyces sp. cultured in sweet potato extract broth media, with 32,970 U/mg (S. tritolerans ARJ 32) and 80,410 U/mg (S. collinus ARJ 38). These results shows that sweet potato extract is potentially an alternative media production for ß-1,3-glucanase enzyme production. Streptomyces sp. had antifungal activity against F. oxysporum and R. solani with inhibition of 23,96% and 32,52% (ARJ 32) and 21,88% and 37,40% (ARJ 38).
Keyword: antifungi, molase, Ubi jalar, enzim ß-1,3-glukanase, kentang

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: