Judul: Ekstraksi Enzimatis dan Filtrasi Naringin dari Kulit Jeruk (Citrus sinensis) Menggunakan Reaktor Membran
Abstrak: Kulit jeruk yang biasa dianggap sebagai limbah mengandung naringin, sebuah komponen flavonoid glikosida yang dapat diekstrak secara enzimatis. Naringin memiliki fungsi antioksidan dan dapat mencegah berbagai penyakit. Ekstraksi enzimatis naringin dari kulit jeruk dilanjutkan dengan filtrasi membran belum banyak dilakukan. Dalam penelitian ini dilakukan penentuan panjang gelombang dan jenis solven untuk kuantifikasi konsentrasi naringin menggunakan spektrofotometer. Kemudian akan dilakukan ekstaksi solven, pemilihan enzim dan optimasi proses ekstraksi naringin dalam reaktor batch. Jenis enzim yang akan dipilih adalah pektinase, selulase dan xilanase. Faktor yang diuji adalah konsentrasi enzim (0,5%; 0,8%; 1,0% dan 1,5% v/v) dan konsentrasi substrat (1,0%, 2,5%, 5,0% w/v). Kemudian dilakukan ekstraksi enzimatis pada kondisi optimum, lalu dilakukan filtrasi membran menggunakan reaktor membran semi batch dengan model dead end. Filtrasi membran dilakukan dengan membran molecular weight cut off (MWCO) 30, 20, 10, 5 dan 4 kDa. Naringin memiliki panjang gelombang sebesar 283 nm dengan solven terbaik adalah buffer natrium asetat (pH 4,6; 0,66 M). Ekstraksi solven menggunakan etanol 80% menghasilkan konsentrasi naringin dan kapasitas antioksidan yang lebih tinggi dari metanol. Enzim yang terpilih adalah Viscozyme CL dengan hasil optimasi yang terpilih adalah konsentrasi enzim 1,0% dan konsentrasi substrat 1,0%. Filtrasi ekstrak enzimatis terpilih kemudian difiltrasi, dengan pemampatan membran yang terjadi untuk seluruh membran adalah cake filtration. Nilai IC50 terendah didapatkan untuk membran dengan MWCO 4, 5, dan 10 kDa, menunjukkan bahwa ekstrak naringin lebih murni untuk ketiga membran tersebut., Many consider orange peel as waste, but it is rich in naringin, a flavonoid glycoside that could be extracted enzymatically. Naringin has antioxidant properties and may prevent against other diseases. Enzymatic extraction of naringin followed by membrane filtration has not yet been widely studied. In this research, determination of solvent and wave length for naringin quantification using spectrophotometer was conducted. Next, solvent extraction of naringin, enzyme selection (xylanase, pectinase and cellulase) and optimization of naringin extraction using batch reactor were conducted. Meanwhile, factors that were tested during optimization are enzyme concentration (0,5%; 0,8%; 1,0%; 1,5% v/v) and substrate concentration (1,0%, 2,5%, 5,0% w/v). Naringin enzymatic extraction was done at optimum condition, followed by membrane filtration using semi batch membrane reactor, with dead end mode. The membrane used has molecular weight cut off (MWCO) 30, 20, 10, 5 dan 4 kDa. Naringin has the wave length of 283 nm with natrium acetate buffer (pH 4,6; 0,66 M) selected as solvent. Solvent extraction using 80% ethanol yields higher concentration and antioxidant capacity compared to methanol. The selected enzyme was Viscozyme CL, with enzyme concentration of 1,0% and substrate concentration of 1,0% selected after optimization. Then, membrane filtration was conducted, and it was found that cake filtration is the main membrane fouling type for all membrane. Lowest IC50 value was found to be the membranes with lower MWCO that are 4, 5, dan 10 kDa, that indicates that naringin extract from those membranes are purer.
Keyword: kulit jeruk, naringin, ekstraksi enzimatis, reaktor, filtrasi membran, orange peel, naringin, enzymatic extraction, reactor, membrane filtration

Judul: Model Perpindahan Massa pada Mikrofiltrasi untuk Penghilangan Limonin dan Naringin dari Jus Jeruk Siam (Citrus nobilis L. var microcarpa)
Abstrak: Bitterness in citrus juice primarily due to the presence of limonin and naringin. Using membrane technology is expected to remove the bitterness. The decreasing of flux is a general membrane problem. Understanding of mass transfer mechanisms, the decreasing of membrane performance could be controlled. The research aimed to remove limonin and naringin from Siam citrus juice by microfiltration, to get the best condition of operation of microfiltration i.e. higher permeate flux and rejection, and to predict mass transfer mechanisms on the microfiltration for removing limonin and naringin from Siam citrus juice. Raw material of the study was Siam citrus. The steps of the study were citrus juice characteristics, effect of transmembrane pressure and cross flow velocity on the permeate flux, rejection, quality of citrus juice, and mass transfer mechanism on the microfiltration of citrus juice according to the total recycle operation mode. Mass transfer mechanism was analyzed by comparing the experimental data with calculation data using thin film models of non-Newtonian fluids based on non-dimensional analysis with Brownian diffusion and shearinduced diffusion approach, Zidney-Colton model, and Davis-Sherwood model. The results showed the fresh citrus juice is a non-Newtonian fluid and a character of dilatant. The limiting flux reached at the transmembrane pressure of 1.84 bar. Optimum condition for microfiltration citrus juice at the transmembrane pressure of 1.74 bar and flow rate of 0.08 ms-1 for 30 minutes, with the permeate flux about 63.16 L m-2h-1. In these conditions, the microfiltration of citrus juice could remove limonin and naringin, respectively by 92.54 % and 71.34 %. The limonin rejection was higher than naringin because limonin is more hydrophobic so that adsorbed onto membrane surface easier. High transmembrane pressure application caused decreasing vitamin C and total soluble solids content in the permeate, respectively by 44.48 % and 38.18 %. Mass transfer mechanisms on the microfiltration of citrus juice strongly depend on citrus juice properties. Presence of particles in citrus juice caused increasing of shear rate on membrane wall, so that increase particle deposition rates from membrane surface. Mass transfer mechanisms on the microfiltration of citrus juice were affected by particle size, particle concentration, and shear rate as showed by close value of experimental data with Zidney-Colton model. Finally, the mass transfer mechanism on the microfiltration Siam citrus juice for removing limonin and naringin could be decribed as mass transfer mechanism by shear-induce diffusion and fresh citrus juice is a dilute suspension.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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