Judul: Sintesis Hidrogel Berbasis Selulosa dari Limbah Padat Industri Agar sebagai Scaffold Imobilisasi Enzim
Abstrak: Hidrogel berbasis polisakarida terbuat dari selulosa yang tersebar merata dalam matriks alginat melalui proses ikatan silang. Limbah padat pengolahan agar memiliki kandungan selulosa yang cukup tinggi. Sintesis hidrogel dengan penambahan selulosa limbah agar sebagai scaffold untuk imobilisasi enzim belum pernah dilakukan. Penelitian bertujuan untuk mendapatkan selulosa dengan ukuran berbeda dari limbah padat pengolahan agar, mengkarakterisasi hidrogel berbasis selulosa dengan ukuran berbeda, dan menentukan pelepasan enzim yang keluar dari hidrogel berbasis selulosa. Tahapan penelitian meliputi persiapan sampel, hidrolisis selulosa, dan sintesis hidrogel dengan variasi makroselulosa (0,5%, b/v) serta mikroselulosa (0,24, 0,48, dan 0,96%, (b/v)). Kadar selulosa diperoleh sebanyak 16,46% dengan satu ukuran makromolekul 10-200 µm sedangkan setelah dihidrolisis menjadi mikroselulosa dengan diameter serat sebesar 597,23 nm. Hidrogel alginat-selulosa menghasilkan rasio swelling dan fraksi gel terbaik sebesar 91,67 ± 11,8% dan 96,57 ± 0,05%. Perlakuan tersebut menghasilkan efektivitas pelepasan enzim terendah pada waktu ke-1 jam sebesar 11,80% dan mencapai puncak sebesar 97,12% pada waktu ke-24 jam. Selulosa dari limbah padat industri pengolahan agar dapat memperbaiki karakteristik hidrogel alginat. Hidrogel alginat-selulosa dapat digunakan sistem pengontrol enzim yang dapat diaplikasikan pada bidang pengolahan makanan dan bioproses., Polysaccharide-based hydrogel is made of cellulose dispersed in an alginate matrix through a cross-linking process. Solid waste of the agar industry has a fairly high cellulose content. The synthesis of hydrogel with the addition of waste cellulose agar as a scaffold for enzyme immobilization has never been done. The aim of the research was to obtain cellulose of different sizes from solid waste from agar processing, characterize cellulose-based hydrogel of different sizes, and to control the released enzyme from the hydrogel. The research includes sample preparation, cellulose hydrolysis, and hydrogel synthesis with addition of macro-cellulose (0.5%, w/v) and micro-cellulose (0.24, 0.48, 0.96% (w/v)). The cellulose content was obtained as much as 16.46% with a macromolecule size of 10-200 µm while after hydrolysis it became microcellulose with a fiber diameter of 597.23 nm. The alginate-cellulose hydrogel produced the best absorption and gel fraction of 91.67 ± 11.8% and 96.57 ± 0.05%, respectively. This treatment resulted in the lowest enzyme release effectiveness at 11.80% and reached a peak of 97.12% at 24 hours. Cellulose from the solid waste of the agar processing industry can improve the characteristics of the alginate. The alginate-cellulose hydrogel can be used as an enzyme control system that can be applied to food processing and bioprocessing.
Keyword: alginate, cellulose, enzyme imobilization, hydrogel, alginate, cellulose, enzyme imobilization, hydrogel

Judul: Synthesis of Ulvan-based Hydrogel from Ulva lactuca Seaweed as Probiotic Immobilization Scaffold
Abstrak: Hidrogel berbasis polisakarida bersulfat ulvan terbuat dengan tambahan polimer pendukung yaitu matriks alginat. Sintesis hidrogel berbasis ulvan-alginat sebagai scaffold untuk imobilisasi probiotik belum pernah dilaporkan. Ulvan merupakan polisakarida bersulfat yang berasal dari rumput laut hijau Ulva. Ulvan diperoleh dari ekstraksi rumput laut Ulva lactuca yang umumnya dilakukan dengan suhu tinggi dan waktu yang lama sehingga diperlukan metode alternatif dalam proses ekstraksinya untuk menghasilkan ulvan dengan kualitas baik namun efisien dalam prosesnya. Alternatif proses ekstraksi yang bisa dilakukan yaitu penggunaan ultrasonikasi yang dapat mengurangi penggunaan pelarut organik dan energi yang tinggi. Penelitian bertujuan mengkarakterisasi Ulva lactuca, menentukan pengaruh Ultrasound-assisted Extraction (UAE) terhadap mutu ulvan, dan menentukan formulasi hidrogel terbaik berbasis ulvan untuk imobilisasi probiotik. Tahapan penelitian meliputi preparasi sampel, optimasi ekstraksi ulvan, dan sintesis hidrogel dengan variasi ulvan (0, 1, 2, 3, dan 4 %)) dan konsentrasi tetap alginat 4%. Ulvan terpilih berdasarkan kandungan sulfat terbesar yaitu 57,20 ± 0,11 % hasil ekstraksi dengan NaOH berbantu ultrasonikasi. Hidrogel ulvan-alginat menghasilkan fraksi gel dan rasio swelling terbaik sebesar 31,88 ± 3,80 % dan 57,18 ± 19,88 % dengan total bakteri probiotik sebesar 8,5 ± 4,9 × 106 log CFU/g. Ulvan dapat berperan sebagai bahan makanan pada hidrogel scaffold sehingga mampu mempertahankan keberadaan bakteri probiotik.
Keyword: imobilisasi probiotik, hidrogel, Ulva lactuca, ulvan

Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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