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Makara Journal of Science
Published by Universitas Indonesia
ISSN : 23391995     EISSN : 23560851     DOI : https://doi.org/10.7454/mss
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Makara Journal of Science publishes original research or theoretical papers, notes, and minireviews on new knowledge and research or research applications on current issues in basic sciences, namely: Material Sciences (including: physics, biology, and chemistry); Biochemistry, Genetics, and Molecular Biology (including: microbiology, physiology, ecology, taxonomy and evolution); and Biotechnology.
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Articles 8 Documents
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Search results for , issue "Vol. 24, No. 1" : 8 Documents clear
Synthesis and Characterization of Chitosan-Polyvinyl Alcohol-Fe2O3 Composite Membrane for DMFC Application Permana, Dian; Ilimu, Edi; Faariu, Nur Mala; Setyawati, Arini; Kadidae, La Ode; Ramadhan, L.O.A.N.
Makara Journal of Science Vol. 24, No. 1
Publisher : UI Scholars Hub

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Abstract

This study investigates the utilization of different compositions of Fe2O3 and polyvinyl alcohol (PVA) to modify chitosan in order to prepare a composite membrane. The membranes were synthesized using the phase inversion method and extensively characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical properties analysis, and water uptake analysis, whereby SEM was used to confirm the morphology of the composite membranes. Different electrochemical properties such as ion exchange capacity, proton conductivity, and methanol permeability of these membranes were also measured. The results showed that increasing the PVA mass improved the water uptake, ion exchange capacity (IEC), and proton conductivity because the PVA addition increased the hydrophilicity of the membrane; thus, the pore surface on the membrane was more open, which also caused higher membrane permeability. However, the methanol permeability values of all composite membranes were lower than that of Nafion. The highest IEC and proton conductivity were obtained for the CS-PVA-H3070 membrane, with values of 4.300 meq/g and 6.71 × 10−2 S·cm−1, respectively. The mechanical strength of these membranes showed that the PVA addition increased the elongation break and decreased the tensile strength of the membrane. The results imply that the chitosan membrane modified with PVA and Fe¬2O3 has a potential for DMFC applications.
Mixed-layer Heat Budget in Western and Eastern Tropical Pacific Ocean during El Niño Event in 2015/2016 Kusuma, Willy Anta; Nur, Muhammad; Khakim, Mokhamad Yusup Nur; Iskandar, Iskhaq
Makara Journal of Science Vol. 24, No. 1
Publisher : UI Scholars Hub

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Temporal variation of mixed-layer heat budget at two contrasting locations, namely, western Pacific (warm water pool) and eastern Pacific (cold tongue) during the extreme El Niño phenomenon in 2015/2016 is evaluated. Oceanic and atmospheric datasets, including sea surface temperature (SST), wind stress, shortwave radiation (SWR), longwave radiation, latent heat flux (LHF), and sensible heat flux are analyzed. A slight warming occurred in the eastern tropical Pacific associated with a positive SST anomaly, which reflected the weakening or reversal of the trade winds. Meanwhile, the western tropical Pacific exhibited a cooling tendency during the development phase of El Niño. Analysis of the mixed-layer heat budget shows that the net heat flux due to SWR and LHF significantly contributes to the warming of the eastern tropical Pacific. The contribution from horizontal advection was extremely small on both sides. The analysis shows that the residual term significantly contributes to cooling (warming) tendency observed in the western (eastern) tropical Pacific. This condition may suggest that residual process due to entrainment and diffusivity played an important role in the evolution of cooling (warming) process in the western (eastern) tropical Pacific.
Thermomechanical Analysis of Various Solid-oxide-fuel-cell Components Using Simple Analog Micrometer Measurements Malik, Yoga Trianzar; Noviyanti, Atiek Rostika; Lestari, Putri Rizka
Makara Journal of Science Vol. 24, No. 1
Publisher : UI Scholars Hub

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The solid oxide fuel cell (SOFC) is a device that can convert the energy stored in gaseous chemicals such as hydrogen into electricity. Because SOFCs are operated at high temperatures, their structures must be stable and durable. The thermomechanical compatibility of SOFC components is the main issue, as negligence in regard to material compatibility leads to cell destruction. In this study, we investigated the thermal expansion coefficient (TEC) of SOFC components, which characterizes their thermomechanical properties. We measured the TEC value of various electrolyte and electrode materials [La9.33Si4O26 (LSO), Ce0.9Gd0.1O1.92 (CGO), La0.8Sr0.2Ga0.8Mg0.2O2.55 (LSGM), LSO-CGO, LSO-LSGM, and La0.7Ca0.3MnO3 (LCM)] using an analog micrometer at temperatures between 298 K and 1073 K. The obtained TEC values matched well with the theoretical references, with errors between 1.80% and 8.00% for LSO, CGO, LSGM, and LCM. The TEC of composite SOFC materials, LSO-LSGM and LSO-CGO, were 10.29 × 10−6 K−1 and 10.10 × 10−6 K−1, respectively. Given the slight difference in their TEC values, these electrolytes would thermomechanically match an LCM cathode.
Highly Sensitive Phenol Biosensor Utilizing Selected Bacillus Biofilm Through an Electrochemical Method Ariyanti, Dita; Iswantini, Dyah; Sugita, Purwantiningsih; Nurhidayat, Novik; Effendi, Hefni; Ghozali, Ali Aulia; Kurniawan, Yehezkiel Steven
Makara Journal of Science Vol. 24, No. 1
Publisher : UI Scholars Hub

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An eco-friendly phenol biosensor from Bacillus biofilm was prepared and investigated. The biofilm, which produced tyrosinase enzyme, was successfully immobilized on a screen-printed carbon electrode surface. A total of 72 Bacillus isolates were utilized because of their capability to produce tyrosinase enzyme in tyrosine media. Among them, Bacillus isolate code 100 was selected because it produced an adequate amount of tyrosinase enzyme and a high potentiostat current. The response surface methodology was also used to optimize the phenol sensing condition through an electrochemical method. Results showed that the optimum condition was achieved after 6 days on a phosphate buffer solution (pH of 8), with an optical density of 0.33. Furthermore, the limits of detection and quantification were 3.0 and 13 ng/L, respectively. The measurements of precision yielded a relative standard deviation of < 5%, which is remarkable. Although the biosensor material was used for 35 days, the current throughout was still maintained at 90%, indicating that the evaluated biosensor material has the potential to be used for phenol monitoring on environmental samples in the near future.
Chemical Modification of Kola-Nut (Cola Nitida) Testa for Adsorption of Cu2+, Fe2+, Mg2+, Pb2, and Zn2+ from Aqueous Solution Slyvanus, Nwafor Ogechi; John, Chukwu Uche; Jnr, Horsfall Mike
Makara Journal of Science Vol. 24, No. 1
Publisher : UI Scholars Hub

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In this study, kola-nut testa samples were modified with 0.1 M acetic acid and 0.1 M EDTA at room temperature. The modified Kola-nut testa samples were then characterized with respect to their pH at point of zero charge, melting point, specific gravity, Fourier-transform infrared (FTIR) spectra, and solubility. The characterization results of the modified Kola-nut testa (MKT) revealed that it was sparingly soluble in water, ethanol, and acetone but insoluble in n-hexane. The MKT had a specific gravity of 0.992 ± 0.020 and exhibited various pH values of 4.50 ± 0.50 and 12.00 ± 0.50 at the point of zero charges. The FTIR spectra of the MKT indicated the presence of –OH and –NH groups at 3310.97 cm−1, alkyl groups at 2928.53 cm−1, and aromatic rings at 1612.27–1529.81 cm−1. The results of the adsorption studies at various time intervals indicated that MKT had the capacity to adsorb Fe2+, Mg2+, Zn2+, Cu2+, and Pb2+ as follows: 1.90 ± 0.30 mg/g, 1.80 ± 0.20 mg/g, 1.40 ± 0.20 mg/g, 0.10 ± 0.01 mg/g, and 0.05 ± 0.01 mg/g, respectively. Thus, Fe2+, Mg2+, and Zn2+ were quantitatively removed from the aqueous solutions, whereas Cu2+ and Pb2+ were not. The adsorption of Fe2+, Mg2+, Zn2+, Cu2+, and Pb2+ by MKT from the aqueous medium was dependent on certain factors such as pH, temperature, adsorbent dosage, contact time, and initial metal-ion concentration.
ZnO/SiO2 Composite as Catalyst for the Transformation of Glycerol to Glycerol Carbonate Krisnandi, Yuni Krisyuningsih; Eckelt, Reinhard; Atia, Hanan; Adam, Martin; Saragi, Indah Revita; Martin, Andreas; Richter, Manfred
Makara Journal of Science Vol. 24, No. 1
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Zinc oxide/porous silica (ZnO/SiO2) composite was used as a catalyst to transform glycerol to glycerol carbonate (GC), a chemical intermediate and monomer for the synthesis of new functionalized polymers. The ZnO/SiO2 catalyst was prepared using the direct precipitation method by mixing zinc sulfate solution with Aerosil 300 silica suspension and adding potassium oxalate solution. Catalytic transformation used glycerol and urea (molar ratio = 1:1) at 140 °C, 40 mbar, and various reaction times (1–6 h). The ZnO catalyst exhibited a high percentage of glycerol conversion of 82.38%; however, the yield of GC and selectivity toward GC were relatively low (i.e., 33.33% and 40.46%, respectively). The presence of silica support (ZnO/(x)SiO2 increased the selectivity toward GC and yield of GC to 74.40% to 77.83% and 57.86% to 64.30%, respectively. Furthermore, although its crystallinity decreased, the reused ZnO/(60)SiO2 catalyst still exhibited a high activity. The scanning transmission electron microscopy image indicated the migration of ZnO on the surface of the composite and the possibility of ZnO-glycolate formation, which were also confirmed by FTIR measurement. Nevertheless, these results showed that ZnO/SiO2 is a promising catalyst for the transformation of glycerol to GC.
Lactic Acid Bacteria from Apis dorsata Hive Possessed Probiotic and Angiotensin-Converting Enzyme Inhibitor Activity Meryandini, Anja; Karyawati, Amor Tresna; Nuraida, Lilis; Lestari, Yulin
Makara Journal of Science Vol. 24, No. 1
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One source of bacteria that has not been widely explored is lactic acid bacteria originating from honeycomb (hive). Timor Island has a wealth of giant honey bees (Apis dorsata). Lactic acid bacteria from the Apis dorsata hive in Timor Island need to be investigated to obtain probiotic candidates with specific functional properties. Lactic acid bacteria were isolated from honeycomb by using de Mann, Rogosa, and Sharpe agar supplemented with 1% of CaCO3. Bacterial isolates that formed clear zones and were Gram-positive and catalase-negative were determined as lactic acid bacteria. The probiotic candidates are isolates that are resistant to bile salts and low pH; susceptible to antibiotics; are able to aggregate, autoaggregate, and coaggregate; and have antibacterial activities. Isolate MC7 was selected as a probiotic candidate and had inhibitory activity against angiotensin-converting enzyme (ACE) with IC50 263,098 ppm. Isolate MC7 showed weak inhibition against ɑ-glucosidase activity. Molecular identification based on 16S rRNA gene showed that MC7 isolate was closely related to Lactobacillus rhamnosus with 100% similarity. Therefore, isolate MC7 was recommended as a probiotic candidate with a functional property as an inhibitor of ACE.
Antifreeze Proteins: Characteristics and Potential Applications Tejo, Bimo Ario; Asmawi, Azren Aida; Rahman, Mohd Basyaruddin Abdul
Makara Journal of Science Vol. 24, No. 1
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The freezing of water is usually fatal to most organisms because it causes extensive damage to cell membranes due to the formation of ice crystals. However, several structurally different classes of antifreeze proteins (AFPs) found in fish, insects, plants, and microorganisms, including bacteria, yeast, and fungi, have been found to be capable of modifying the growth of ice crystals by thermal hysteresis and ice recrystallization inhibition. This unique property could potentially be applied to medicine and the industry as it is useful when low-temperature storage is required and ice crystallization must be avoided. However, the application of AFPs today is not economically viable due to the complexity of the large proteins, the laborious procedures required, and the low yields obtained. A wide range of peptides mimicking their parent proteins were recently successfully designed and chemically synthesized. The developed approaches present new opportunities to understand the structure–function relationship of small-structured peptides with antifreeze properties. This mini-review highlights the diversity, classification, and properties of AFPs. The emerging applications of short mimetic peptides of AFPs and their potential application are also described.

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