Judul: Aplikasi Enzim Laktase Terimobilisasi dengan  Alginate Beads untuk Penurunan Kadar Laktosa pada Susu
Abstrak: Susu mengandung jenis gula yang spesifik yaitu laktosa. Terdapat beberapa kalangan yang tidak dapat mengonsumsi susu dan produk turunannya karena mengidap intoleransi laktosa. Salah satu cara untuk menurunkan kandungan laktosa dalam susu adalah memecah laktosa menjadi glukosa dan galaktosa dengan bantuan enzim laktase. Metode penurunan kadar laktosa yang digunakan pada skala industri adalah metode enzim terlarut yang dinilai tidak efisien karena memerlukan enzim laktase baru di setiap batch produksi. Metode imobilisasi enzim menjadi salah satu metode yang dapat diterapkan untuk mengefisienkan penggunaan enzim laktase. Penelitian ini bertujuan mengkaji penggunaan metode imobilisasi enzim laktase dengan manik alginat pada proses penurunan kadar laktosa dalam susu, mengkaji pengaruh perlakuan terhadap aktivitas dan stabilitas enzim serta karakteristik sensori susu. Penelitian dilakukan menggunakan Rancangan Acak Lengkap Faktorial (RALF) dengan 2 faktor yaitu konsentrasi enzim (0,1% dan 0,2%) dan waktu inkubasi (24 jam dan 38 jam). Hasil penelitian menunjukkan bahwa setiap kombinasi faktor perlakuan menghasilkan kadar laktosa yang berbeda mulai dari 2,79%-3,35%. Aktivitas enzim laktase terimobil juga mengalami penurunan setelah pemakaian berulang karena terdapat enzim laktase yang terlepas dari matriks Ca-alginat. Hasil uji sensori menunjukkan bahwa perlakuan yang dilakukan selama proses penurunan kadar laktosa dengan metode imobilisasi enzim berpengaruh secara signifikan terhadap atribut rasa, tekstur, dan keseluruhan susu., Milk contain specific type of sugar which is lactose. There are some people who cannot consume milk and its derivative products because they suffer from lactose intolerance. One way to lower the lactose content in milk is to break down lactose into glucose and galactose with the help of the lactase enzyme. Method of reducing lactose content that usually use in industrial scale is dissolved enzyme method which considered inefficient because it requires a new enzyme in each batch of production. The enzyme immobilization is one method that can be applied to efficiently the use of lactase enzyme. This study aimed to simulate the application of lactase enzyme immobilization with alginate beads in the process of reducing lactose content in milk, assessing the effect of treatment on enzyme activity and stability as well as sensory characteristic of milk. The study was conducted using Factorial Complete Randomized Design (RALF) with 2 factors, namely enzyme concentration (0.1% and 0.2%) and incubation time (24 hours and 38 hours). The results showed that each combination of treatments produced different lactose levels ranging from 2.79%-3.35%. Repeated use of immobilized lactase enzyme can decrease its activity because there is a lactase enzyme released from the Ca-alginate matrix. The results of sensory tests show that the treatment carried out during the process of reducing lactose content with the enzyme immobilization method has a significant effect on the taste, texture, and overall attributes of milk.
Keyword: enzim laktase, imobilisasi enzim, laktosa, manik alginat, susu, alginate beads, enzyme immobilization, lactase enzyme, lactose, milk

Judul: Amobilisasi Sel Lactobacillus plantarum B134 dan β-Galaktosidase dengan Natrium Alginat dan Potensi Hidrolisisnya pada Susu UHT Skim dan Berlemak
Abstrak: Susu merupakan salah satu produk pangan yang memiliki nilai gizi yang baik. Sayangnya, konsumsi susu Indonesia hanya 11.09 per liter per kapita per tahun. Minimnya konsumsi susu dapat disebabkan karena intoleransi laktosa yaitu ketimakmampuan tubuh untuk mencerna laktosa karena tidak memiliki β-galaktosidase. Solusi alternatifnya adalah mengolah susu sampai kadar laktosanya menjadi rendah menggunakan β-galaktosidase dari mikroorganisme. L. plantarum B134 merupakan bakteri asam laktat dari Indonesia yang memiliki aktivitas β-galaktosidase yang tinggi. Penggunaan β-galaktosidase lebih efisien apabila dilakukan teknik penjebakan (amobilisasi) sehingga dapat digunakan berulang dan dapat menurunkan biaya produksi. Natrium alginat merupakan matriks penjebak yang murah dan aman untuk mengamobilisasi enzim dan sel. Penelitian ini bertujuan untuk menghidrolisis laktosa susu UHT berlemak dan skim dengan menggunakan sel L. plantarum B134 amobil dan β-galaktosidase amobil. Tahapan penelitian ini meliputi (1) optimasi amobilisasi sel L.plantarum B134 dan β-galaktosidase dengan natrium alginat, (2) pengaruh pH dan suhu pada sel L.plantarum B134 dan β-galaktosidase amobil, (3) stabilitas pH dan suhu β-galaktosidase amobil, (4) hidrolisis laktosa pada susu UHT berlemak dan skim, (5) keterulangan pemakaian beads sel L. plantarum B134 amobil dan β-galaktosidase amobil, dan (6) penyimpanan β-galaktosidase amobil. Sel L. plantarum B134 amobil mencapai optimum pada 1% natrium alginat, 0.1 M CaCl2, dan 12% b/v sel. Aktivitas β-galaktosidase mencapai optimum pada pH 6.5 dan suhu 45ºC selama 5 menit. Efisiensi amobilisasi sel L. plantarum B134 amobil adalah 28.95%. Laktosa susu UHT berlemak terhidrolisis sebesar 85.45% selama 12 jam sedangkan pada susu UHT skim sebesar 91.26% selama 9 jam. Sel L. plantarum B134 amobil dapat digunakan untuk kedua tipe susu UHT sebanyak 4 kali. β-Galaktosidase amobil mencapai optimum pada 1% natrium alginat, 0.1 M CaCl2, dan 26 U β-galaktosidase. Aktivitas β-galaktosidase amobil mencapai optimum pada pH 5.5, suhu 35ᵒC selama 15 menit. Efisiensi amobilisasi β-galaktosidase amobil adalah 96.69%. Stabiltas pH tercapai pada pH 5 dan stabilitas suhu pada 30ºC. Nilai Km dan Vmaks β-galaktosidase masing-masing sebesar 30.487 mM dan 1.742 μmol/menit. β-Galaktosidase amobil mereduksi 80.55% laktosa UHT belemak selama 15 jam dan 93.06% laktosa UHT skim selama 6 jam. β-Galaktosidase amobil dapat digunakan 3 kali untuk hidrolisis laktosa susu UHT berlemak dan 6 kali untuk susu UHT skim. Setelah penyipanan 35 hari pada suhu 4ºC, β-galaktosidase masih memiliki aktivitas relatif β-galaktosidase sebesar 52.01%.
Keyword: amobil, β-galaktosidase, Lactobacillus plantarum B134, natrium alginat, UHT

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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