Judul: Potensi Antibakteri Ekstrak Mikroalga Laut Chaetoceros Gracilis Terhadap Bakteri Staphylococcus Epidermidis Secara In Vitro
Abstrak: Resistensi bakteri terhadap antibiotik menjadi satu kendala dalam pengobatan jerawat. Resistensi antibiotik dapat dicegah melalui penggunaan senyawa antibiotik baru. Mikroalga laut Chaetoceros gracilis dapat dijadikan sebagai sumber antibiotik baru dalam pengobatan jerawat. Tujuan penelitian ini adalah untuk menentukan aktivitas antibakteri dari C. gracilis terhadap bakteri Staphylococcus epidermidis secara in vitro. Aktivitas antibakteri diuji berdasarkan indeks penghambatan dan kebocoran membran sel. Produksi biomassa mikroalga menghasilkan rendemen sebesar 0.12 g.L-1. Rendemen ekstrak mikroalga C. gracilis yang diperoleh sebesar 47,40%. Ekstrak mampu menghambat pertumbuhan S. epidermidis dilihat dari indeks penghambatan yang berkisar antara 0.71-1.58. Nilai konsentrasi hambat minimum (KHM) ekstrak sebesar 0,4 mg.mL-1 serta telah menyebabkan kebocoran membran sel bakteri. Komponen aktif yang terkandung pada ekstrak terdiri atas alkaloid dan steroid.
Keyword: resistensi antibiotik, ekstrak C. gracilis, S. epidermidis, indeks penghambatan, KHM

Judul: Ektraksi senyawa antibakteri dari mikroalga laut jenis chaetoceros gracilis dan uji aktivitasnya terhadap beberapa bakteri
Abstrak: Penelitian terhadap Chaetoceros gracilis, salah satu jenis mikroalga yang dominan pada perairan lepas pantai Indonesia, bertujuan untuk menentukan pola pertumbuhan mikroalga tersebut pada suhu ruang, mengekstrak senyawa antibakterinya, dan menguji aktivitas antibakteri tersebut terhadap beberapa bakteri. C. gracilis dikultivasi dalam medium Guillard pada suhu ruang dengan kepadatan awal 1,0x10¹ sel/ml, pengaturan aerasi, dan pemberian cahaya sebesar 1500 luks dari lampu TL 20 watt. Penentuan pola pertumbuhan dilakukan dengan metode hitungan langsung di bawah mikroskop, mengkonversi nilai kepadatannya ke dalam log, dan memplotkannya pada milimeter blok sehingga diperolah kurva pertumbuhan. Ekstraksi senyawa antibakteri ekstraseluler dan intraseluler dilakukan dengan memodifikasi prosedur umum dari metode Quinn (1988) dan Pratt (1945). Setelah diperoleh ekstrak kasar intraseluler dan ekstraseluler antibakteri, dilakukan uji aktivitasnya terhadap bakteri Gram negatif (E. coli dan Pseudomonas sp.) dan Gram positif (B. subtilis dan S. aureus) dengan memodifikasi metode Caliberated Dichotomous Sensitivity (CDS) test. Antibiotik streptomycin dan aquadest steril digunakan sebagai kontrol positif dan negatif. Kurva pertumbuhan C. gracilis selama 28 hari umur kultur meliputi 5 fase, yaitu fase lag (adaptasi) dari hari 0-1, fase log (pertumbuhan cepat) dari hari 2-10, fase decline (penurunan laju pertumbuhan) dari hari 11-13, fase stasioner dari hari 14-22, dan fase kematian mulai hari ke-23. Warna kultur fase lag sampai fase kematian adalah bening, coklat bening, coklat bening, coklat pekat, dan coklat keruh, dengan kisaran pH antara 8,1-8,7. cinta Pemanenan kultur dilakukan pada semua fase, masing-masing sebanyak 1700 ml. Ekstraksi terhadap biomassa dilakukan pada semua fase, kecuali fase lag, karena biomassa yang dihasilkan sangat sedikit. Sebagai hasilnya, diperoleh ekstrak kasar intraseluler berupa padatan lengket berwarna hijau kecoklatan dengan kisaran 7,1-10,8 mg/1700 ml kultur, dan ekstrak kasar ekstraseluler berkisar antara 1.676-3.534 mg/100 ml filtrat berupa serbuk putih sampai putih hijau kecoklatan, dengan jumlah terbesar pada fase kematian (intraseluler maupun ekstraseluler)…dst
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Judul: Characteristic of Overshooting Top (OT) Based on  Himawari  8  Satellite  as  a  Convective  Cloud  Feature  that  Generates  Extreme Weather in the Java Island Region
Abstrak: Overshooting Top (OT) is a feature at the top of a convective cloud that is associated with extreme weather. Research on OT in tropical Indonesia is still very limited. The existence of geostationary satellites with wide area coverage and fast frequency observations is useful for observing the fast dynamics of the OT life cycle. Therefore, this study intends to analyze the relationship between OT and extreme weather, updraft and thermodynamic conditions of OT when extreme weather occurs, the best objective method for detecting OT in the day time and night time, and the spatiotemporal distribution of OT in the tropical region of Java Island during the 2018-2021 period. Based on visual analysis using visible channel and Himawari 8 sandwich products, 87% of extreme weather events in Java were accompanied by the appearance of OT. It indicates that the presence of the OT pattern is a convection cloud pattern or feature that is closely related to extreme weather events for the Java Island region. The existence of a time lag between the appearance of OT and extreme weather events on Java Island indicates that the OT of convection cloud can be used as a precursor or nowcasting for the appearance of extreme weather. Most of the convective cloud OT features during extreme weather events on Java Island have altitude that were only able to exceed the altitude of the equilibrium level and few were able to exceed the tropopause level of 9 km – 16 km. The difference in atmospheric conditions during extreme weather events on Java Island, which is in the tropics and subtropics, is a strong and unstable convective energy condition characterized by a larger CAPE, as well as unstable KI, LI, SI and TTI values. It is offset by kinematic factors in the form of a weak vertical wind shear (bulk wind shear 0-6 km) and a higher freezing point height. The difference between extreme weather events in the Java Island region and other tropical regions compared to subtropical regions is the strong updraft speed of convection clouds. The IRW Texture COMB algorithm based on the IRW-Texture Gradient modification and the COMB algorithm shows a significant increase in quality for detecting OT and non-OT pixels in Java. Rainy days with rainfall > 50 mm/day are very common in areas with an altitude of > 500 m. On the other hand, the level of convection activity which is indicated by the presence of OT and lightning is significantly reduced in this area. OT of convective clouds appear more frequently during the DJF season and less frequently during the JJA season. OT often appears during the day time and rarely at night time. Most OTs appear in the central part, away from the south and north coasts of Java Island during the day, while OTs that appear near the south and north coasts of Java Island can appear in the morning or afternoon.
Keyword: convective clouds, extreme weather, Overshooting Tops, Himawari 8 Satellite