Judul: Isolasi Dan Identifikasi Bakteri Kitinolitik Sebagai Agens Biokontrol Cendawan Patogen Pada Kokon Cricula Trifenestrata (Lepidoptera: Saturnidae).
Abstrak: Cricula trifenestrata merupakan salah satu serangga penghasil sutra alam yang belum didomestikasi, sehingga dikenal sebagai ulat sutra liar. C. trifenestrata mengeluarkan air liur yang mengandung protein dan menjadi bahan pembentukan kokon. Kokon ini dikumpulkan untuk diolah menjadi benang sutra. Sutra hasil olahan kokon C. trifenestrata memiliki nilai ekonomi yang tinggi di pasaran karena memiliki serat berwarna kuning emas yang merupakan warna khas kokonnya. Hal inilah yang menjadi pembeda antara C. trifenestrata dengan ulat sutra lainnya. Salah satu patogen yang dikenal menyerang kokon ulat sutra ialah cendawan. Serangan cendawan dapat mengakibatkan kualitas dan kuantitas benang sutra yang dihasilkan mengalami penurunan. Di India, kegagalan panen kokon akibat serangan cendawan mencapai 30-40%. Cendawan memiliki dinding sel yang tersusun atas kompleks kitin dan merupakan target utama bagi agens anti cendawan, misalnya fungisida kimiawi. Namun, adanya dampak negatif yang ditimbulkan dari penggunaan fungisida kimiawi menyebabkan perlu dicari fungisida biologi seperti memanfaatkan bakteri kitinolitik potensial yang mampu menghambat bahkan membunuh cendawan patogen karena menghasilkan enzim kitinase. Bakteri kitinolitik memiliki potensi tinggi sebagai agens pengendali biologi terhadap cendawan patogen pada C. trifenestrata sehingga penurunan kualitas dan kuantitas sutra emas dapat dihindari. Tujuan penelitian ini ialah untuk mengisolasi bakteri kitinolitik dan cendawan patogen asal kokon C. trifenestrata serta identifikasi dan potensinya sebagai biokontrol. Hasil isolasi dari kokon C. trifenestrata di Desa Babakan Lebak, Dramaga, Bogor didapatkan 10 isolat cendawan dan 36 isolat bakteri kitinolitik dengan Indeks Kitinolitik (IK) bervariasi. Isolat bakteri kitinolitik BSEP.3 diketahui mampu menghambat isolat cendawan CSAJ.2 yang diduga sebagai cendawan patogen dengan persentase penghambatan sebesar 50%. Kitinase yang dihasilkannya sebesar 5.11 U/mL pada jam ke-15 waktu inkubasi. Ekstrak kasar kitinasenya memiliki persentase penghambatan sebesar 47.5%. Sekuen hasil amplifikasi gen penyandi 16S rRNA dan konstruksi pohon filogenetik menunjukkan bahwa bakteri BSEP.3 memiliki kemiripan 98% dengan Bacillus amyloliquefaciens galur B5. Sekuen hasil amplifikasi daerah ITS rDNA dan konstruksi pohon filogenetik menunjukkan bahwa isolat cendawan CSAJ.2 memiliki kemiripan 100% dengan Trichoderma virens galur TV242. Aplikasi kitinase ekstrak kasar isolat bakteri kitinolitik BSEP.3 menunjukkan kemampuannya dalam menghambat pertumbuhan cendawan patogen pada kokon ulat sutra emas C. trifenestrata baik secera preventif maupun kuratif.
Keyword: Bacillus amyloliquefaciens, Trichoderma virens, kitinase

Judul: Isolasi dan Identifikasi Bakteri Kitinolitik Penghambat Pertumbuhan Cendawan Patogen Asal Kokon Cricula trifenestrata
Abstrak: Gold Silkworm’s cocoon is a coat of Cricula trifenestrata’s pupa that include part of life cycle. The fiber which is resulted from processing cocoon has high economic value because the specific of gold colour that doesn’t have any else cocoon. However, on the process often occurred many problems that could decrease quantity and quality of cocoon, such as attack from pathogenic fungi. For controlling of the pathogenic fungi has been used chemical agent, but using regularly caused some negative effects. As alternative using chitinolytic bacteria as biocontrol, because of chitin is the highest component of the fungi cell wall. Therefore the objectives of this research were to isolate and identify of chitinolytic bacteria that inhibited fungi pathogen which isolated from cocoon of C. trifenestrata. 17 strains chitinolytic bacteria were isolated from two samples cocoon of health pupa and sick pupa. There were four isolates CH2, CH10, CS1, and CS4 had highest value of chitinolytic index. CH10 and CS1 strains showed highest chitinase activity, both isolates were identified using MicrogenTM GenA+B ID System and categorized as Shewanella putrefaciens. Scopulariopsis sp. and FC (unidentified) were isolated from cocoon of sick pupa. Strain CH10 inhibited FC on culture bacteria test but not from its in chitinase. Scopulariosis sp. had been inhibited by culture and its chitinase.
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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.
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