Judul: Studi awal immobilisasi enzim lipase pada membran dan aplikasinya untuk produksi biodiesel
Abstrak: Biodiesel as an altemative replacement diesel fuel, has several advantages, such as produced from renewable source, biodegrable and low emission. Commercially, biodiesel is produced by transesterification reaction using alkaline catalyst. One of disadvantage using alkaline catalyst is able to cause saponification. Biocatalyst, such as lipase enzyme, can solve it. In addition, using lipase enzyme has several advantages such as reaction can be operated in mild condition, glycerol can be easily separated and fiee fatty acid contained in oil can be completely converted to biodiesel. The high cost of the lipase enzyme in an industrial process is still limited. Immobilization of lipase enzyme in membrane is one of an altemative to solve that problem. The aim of using membrane in immobilization process is separating product from reactant and biocatalyst. Product can be separated easier and need less energy and cost.
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Judul: Produksi Biodiesel Menggunakan Lipase Amobil Pada Kitin Dalam Reaktor Unggun Diam (Fixed Bed Reactor).
Abstrak: Produksi biodiesel menggunakan katalis biologis tidak memerlukan proses pemurnian produk dan kebutuhan energi yang lebih rendah dibandingkan penggunaan katalis kimiawi. Meski demikian, biokatalis tidak banyak digunakan dalam industri karena harganya yang mahal. Oleh karena itu, metode imobilisasi enzim menjadi alternatif solusinya. Kitin dapat digunakan sebagai support dalam proses imobilisasi enzim karena mengandung gugus amino yang menyediakan tempat ikatan untuk protein. Produksi biodiesel pada skala laboratorium banyak dilakukan secara batch. Untuk implementasi enzim amobil dalam dunia industri, reaktor batch kurang efisien. Oleh karena itu dibutuhkan alternatif proses yaitu menggunakan reaktor kontinyu, salah satunya dengan menggunakan fixed bed reactor. Berdasar pada hal tersebut, penelitian ini bertujuan untuk memperoleh lipase yang terimobilisasi pada kitin dengan nilai derajat imobilisasi terbaik dari variasi waktu aktivasi kitin, konsentrasi lipase dan waktu inkubasi selama imobilisasi; memperoleh hasil terbaik dari konversi minyak menjadi metil ester dari variasi konsentrasi substrat dan suhu reaksi; dan memperoleh konversi metil ester yang berlangsung secara kontinyu pada fixed bed reactor. Pada penelitian ini kitin diaktivasi dengan glutaraldehid sebelum digunakan sebagai support. Waktu aktivasi kitin bervariasi antara 1 jam hingga 3 jam. Setelah itu kitin diinkubasi dalam larutan lipase berbagai konsentrasi mulai dari 0.044 mg mL-1 hingga 0.264 mg mL-1 dan didiamkan dalam cold room dengan variasi waktu yang berbeda-beda pula yaitu 14 jam hingga 24 jam. Perlakuan yang menghasilkan persentase tertinggi dari lipase yang terikat pada kitin adalah aktivasi kitin dengan glurataraldehid selama 1 jam 30 menit. Konsentrasi lipase yang menghasilkan derajat imobilisasi tertinggi adalah 0.22 mg mL-1. Sedangkan waktu inkubasi kitin dalam larutan lipase yang menghasilkan derajat imobilisasi tertinggi adalah inkubasi selama 18 jam pada cold room. Lipase amobil kemudian digunakan dalam proses transesterifikasi minyak sawit untuk memperoleh konversi metil ester. Suhu transesterifikasi yang digunakan bervariasi antara 40 oC hingga 55 oC dan rasio mol minyak dan metanol sebesar 1:3 hingga 1:6. Konversi metil ester tertinggi setelah 8 jam reaksi diperoleh pada kondisi suhu reaksi 45 oC dan rasio mol minyak dan metanol sebesar 1:4. Kestabilan lipase amobil dipelajari melalui reaksi transesterifikasi yang berlangsung dalam reaktor kontinyu fixed bed reactor selama 50 jam tanpa henti. Lipase amobil menghasilkan konversi metil ester sebesar 67.95% dan aktivitasnya terus mengalami penurunan seiring bertambahnya waktu produksi.
Keyword: biodiesel, fixed bed reactor, lipase amobil, transesterifikasi

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