Judul: Deteksi L-DOPA dan Tirosinase dari Biopigmen Melanin Asal Bakteri Tanah serta Potensinya sebagai Antioksidan
Abstrak: Melanin merupakan pigmen berwarna coklat kehitaman yang terbentuk oleh polimerisasi senyawa fenolik dan indolik. Melanin disintesis menggunakan L- tirosin sebagai prekusor oleh enzim tirosinase. Enzim tirosinase akan merubah L- tirosin menjadi L-DOPA yang nantinya akan berubah menjadi melanin. Penelitian ini bertujuan mengevaluasi produksi melanin oleh beberapa bakteri asal tanah serta potensinya sebagai antioksidan. Diperoleh 3 dari 6 isolat bakteri yang diduga mampu menghasilkan melanin, yakni Sp 4, Sp 23, dan STIL 84. Ketiga isolat bakteri tersebut diukur konsentrasi L-DOPA serta aktivitas enzim tirosinasenya. Aktivitas enzim tirosinase pada ketiga isolat optimum pada hari ke-8. Aktivitas spesifik enzim tirosinase tertinggi dimiliki oleh isolat Sp 4 sebesar 4283,819 U/mg dan konsentrasi L-DOPA tertinggi dimiliki oleh isolat Sp 23 yakni 0,215 mg/mL. Ekstrak melanin yang dihasilkan oleh isolat Sp 4 memiliki karakteristik berupa serapan panjang gelombang maksimum yang mirip dengan standar melanin. Identifikasi berdasarkan gen 16S rRNA dilakukan terhadap isolat Sp 4 dan diperoleh hasil bahwa isolat Sp 4 teridentifikasi sebagai Pseudomonas oryzihabitans. Pengukuran nilai SPF dan uji antioksidan pada ekstrak melanin yang dihasilkan P. oryzihabitans Sp 4 menunjukkan hasil berupa nilai SPF ekstrak melanin berkategori proteksi medium pada konsentrasi 125 µg/mL dan hasil uji antioksidan menampilkan hasil IC50 sebesar 51,71±0,28 µg /mL. Kata kunci : Antioksidan, melanin, Pseudomonas, tirosinase, UV-protector, Melanin is a brown-black pigment formed by the polymerization of phenolic and indolic compounds. The tyrosinase enzyme convert L-tyrosine to L-DOPA which will later turn into melanin. This study aims to evaluate the production of melanin by bacteria and their potential as antioxidant. The result showed that 3 out of 6 bacteria were suspected of producing melanin (Sp 4, Sp 23, and STIL 84). These bacteria were then tested to determine the L-DOPA concentrations and tyrosinase enzyme’s activities. The tyrosinase enzyme activity in three isolates reached the optimum on the 8th days of incubation. The highest specific activity of the tyrosinase enzyme was possessed by Sp 4 of 4283.819 U/mg and the highest L- DOPA concentration was 0.215 mg/mL by Sp 23. The melanin extract produced by Sp 4 has the maximum wavelength absorption similar to the melanin standard. The Sp 4 was identified based on the 16S rRNA gene and had the closest similarity with Pseudomonas oryzihabitans. Measurement of the SPF and antioxidant value of the melanin extract produced by P. oryzihabitans Sp 4 showed that the SPF value was in the medium protection (125 µg/mL) while the antioxidant activity had an IC50 value of 51.71 ± 0.28 µg /mL. Keywords: Antioxidant, melanin, Pseudomonas, tyrosinase, UV-protector
Keyword: Antioxidant, melanin, Pseudomonas, tyrosinase, UV-protector

Judul: Detection of L-DOPA and Tyrosinase Enzyme Activity in Black Biopigment Production of Micromonospora chalcea HV1.P3
Abstrak: Aktinomiset merupakan salah satu jenis mikrob potensial yang tersebar di wilayah lautan Indonesia. Mikrob ini dapat memproduksi beragam jenis senyawa bioaktif salah satunya adalah biopigmen. Aktinomiset tertentu mampu memproduksi pigmen berwarna coklat tua yang biasa disebut melanin. Pigmen melanin dapat diproduksi menggunakan L-tirosin sebagai prekursor melalui kerja enzim tirosinase. Tirosinase mengubah tirosin menjadi L-DOPA (3,4- dihidroksifenil-L-alanin), selanjutnya diubah menjadi dopakrom dan diautooksidasi menjadi indol-5,6-kuinon, kemudian secara spontan dipolimerisasi menjadi DOPA-melanin. Penelitian ini bertujuan mendeteksi L-DOPA, menentukan aktivitas enzim tirosinase dan aktivitas spesifik optimumnya dalam produksi biopigmen berwarna hitam dari Micromonospora chalcea HV1.P3. Analisis gen 16S rRNA menunjukkan bahwa isolat aktinomiset HV1.P3 memiliki kesamaan terdekat dengan M. chalcea strain 1464-217L. Kultur produksi dari aktinomiset tersebut dilakukan pengujian untuk mendeteksi adanya kandungan L DOPA, aktivitas enzim tirosinase dan aktivitas spesifiknya menggunakan spektrofotometer UV-Vis. Konsentrasi L-DOPA yang diukur selama 6 hari berturut turut menunjukkan adanya peningkatan secara bertahap dari hari ke-1 terukur sejumlah 0.009 mg/mL hingga tertinggi pada hari ke-5 sejumlah 0.101 mg/mL. Aktivitas spesifik tirosinase optimum diperoleh pada hari ke-4 inkubasi yakni 110.825 U/mg dengan nilai aktivitas enzim tirosinase sebesar 3400 U/mL dan kadar protein terukur adalah 0.0307 mg/mL. Kata kunci: Aktinomiset, L-DOPA, melanin, Micromonospora, tirosinase, Actinomycetes, producing numerous different types of bioactive compounds, one of which is biopigment. Actinomycetes are popular as hyper producers of dark-brown color called melanin. L-tyrosine helps produce melanin, the pigment that makes up skin color through a synthesis regulated by the enzyme tyrosinase. The tyrosinase converts tyrosine to L-DOPA (3,4-dihydroxyphenyl-L alanine), then converted to dopachrome and auto-oxidized to indole-5,6-quinone, then spontaneously polymerized to DOPA-melanin. This study aims to detect L DOPA, determine the activity of the tyrosinase enzyme and its optimum specific activity in black biopigment production of Micromonospora chalcea HV1.P3. Analysis of the 16S rRNA gene showed that the actinomycete isolate HV1.P3 had the closest similarity with M. chalcea strain 1464-217L. The production culture of the actinomycete was tested to detect the presence of L-DOPA content, tyrosinase enzyme activity and specific activity using a UV-Vis spectrophotometer. The concentration of L-DOPA measured for 6 consecutive days showed a gradual increase from day 1 measured at 0.009 mg/mL to the highest on day 5 at 0.101 mg/mL. The optimum specific activity of tyrosinase was obtained on the 4th day of incubation, with a value of 110.825 U/mg and tyrosinase enzyme activity value at 3400 U/mL, while the measured protein content was 0.0307 mg/mL. Keywords: Actinomycete, L-DOPA, melanin, Micromonospora, tyrosinase
Keyword: Actinomycete, L-DOPA, melanin, Micromonospora, tyrosinase

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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