Key Engineering Materials Vol. 811

Abstract: A method to protect the hydroxyl group of quinine via esterification is developed. The method uses acetyl and benzoyl as the protection group. The method employs no catalyst that generates reasonable yield at 83% for acetyl and 73% for benzoyl. This catalyst free method emphasizes on the importance substrate reactivity to achieve free catalyst procedure. Ester form of quinine synthesized might be further functionalized for various aims in accordance to its rich functional group and building block of quinine.

Abstract: Starch-based hydrogels are biodegradable and biocompatible materials which have large surface area and are able to absorb a large amount of water. Hydrogels can be made of inclusion complexes between starch and hydrophobic guest molecules, such as starch-oleic acid complexes. The resulting hydrogels have advantages as the inclusion complexes can prevent the starch retrogradation in the hydrogel. For this purpose, inclusion complexes between starch and oleic acid were prepared by mixing cassava starch and oleic acid at 85 °C with varying complexation times(1 hour, 2 hours and 5 hours). Optimum result (product yield ~67%) was obtained by heating the reaction for 5 hours at 85 °C. In addition, the concentrations of oleic acid for complexation were varied at 10%, 20% and 50% (v/w) (calculated based on the weight of starch). The results showed that the maximum amount of oleic acid which could be complexed with starch was around 10% (v/w). The resulting products were characterized by Fourier Transform Infra Red (FTIR) spectroscopy, X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). FTIR results of the complexes showed vibration peaks at around 3600-3000 cm^-1 (-OH), 2900-2800 cm^-1 (-CH₂), 1300-1200 cm^-1 (C-O-C glycosidic bonds) and 1100-1000 cm^-1 (C-C and C­-O). The XRD results showed that the resulting complexes were crystalline and constructed of V₆-amylose, which was evidenced by the appearance of peaks at 2θ of 13.06° and 20.38°. Some complexes also showed interesting diffractions at 2θ of 17.07° and 30.26°. TGA results showed that the complexes started to decompose at either around 277 °C or 285 °C compared to starch which started to decompose at around 303 °C. SEM studies showed that the resulting complexes formed spheres with concave centers close to the shape of doughnuts. The complexes offered great potential to be applied as hydrogel materials, such as round hydrogels with initial average diameters of around 2.6 mm and 8.3 mm.

Abstract: Nowadays the development of biodiesel production as an alternative renewable energy became crucial. The reusability of enzymes as biocatalysts in biodiesel production has limitations and can be improved by the immobilization process onto the appropriate solid support, such as polyethersulfone (PES). Polyethersulfone has been synthesized utilizing microwave-assisted reaction method (400 W, 170 °C, 60 minutes). Nitration reaction of PES was performed by refluxing the synthesized PES with the mixtures of H₂SO₄ (0 °C, ± 30 minutes) and HNO₃ (25 °C, 4 hours). The –NO₂ groups of the synthesized PES-NO₂ was subsequently reduced to be PES-NH₂ using SnCl₂.2H₂O as reducing agent by reflux method (60 °C, ± 3 hours). The structure of PES and its derivatives was confirmed by FTIR and ¹H-NMR. Candida antarctica lipase was successfully immobilized onto the synthesized PES and its derivatives, which were confirmed by its FTIR spectra and its activity tests of the supernatants in hydrolyzing p-nitrophenol palmitate (pNPP) into p-nitrophenol (pNP). The results showed that the conversion percentage of pNPP to become pNP were 20.6% (free enzyme), 18.9% (PES-enzyme), and 3.7% (PES-NH₂-enzyme). The decrease in the supernatant enzyme activity showed that the enzyme has been successfully immobilized through physical adsorption onto the synthesized polymers.

Abstract: Superoxide dismutase (SOD) is an Mn-containing enzyme that catalyzes the conversion of superoxide (O₂^•−) into O₂ and H₂O₂. To develop a small, non-protein Mn-containing SOD mimic, an [Mn(salen)Cl] complex was synthesized from MnCl₂.4H₂O and H₂salen. The product yielded 75-90% reddish dark brown crystals indicative of the presence of manganese(III) metal ions. An elemental analysis showed that the compound contained: C = 48.36%; H = 4.34%; and N = 7.13%. Infrared spectra of this compound showed peaks at: υ(OH)=3426 (medium), υ(C=N)=1634 (very high), υ(CO)=1292 (high). An ESI-MS analysis (m/z) showed the presence of ionic species from the complex including (salen)(H⁺) = 269.0 and [Mn(salen)]⁺ = 320.9. Conductivity measurements revealed that the compound is neutral with a molar conductivity of 0.17 mS. Its magnetic moment of 5.2 BM was obtained from a magnetic susceptibility balance measurement, showing that the compound is paramagnetic. The SOD activity of this compound was given by IC₅₀ = 2.5 ± 0.3 µM in a non-enzymatic riboflavin photoreduction in vitro test.

Abstract: Bioplastics are biodegradable polymers which can be produced by bacteria. The production occurs when the bacteria grow in a medium containing a minimum amount of key nutrients, such as nitrogen, magnesium, and phosphorus but is rich of carbon source. It is known that some bacteria from the genus Halomonas can produce bioplastics compound such as polyhydroxybutyrate (PHB). This study focused to evaluate the potential of Halomonas elongata BK-AB8 in producing PHB. The bacteria were grown on a medium containing nile red. The grown bacterial colony exhibited orange luminescence when exposed under UV light indicating that the bacteria was able to produce bioplastics. The bioplastic production was conducted by growing the bacteria in the modified growth medium at 37 °C for 22 hours with aeration rate of 150 rpm. The resulting bioplastic was extracted using a mixture of chloroform−NaOCl (1:1), and subsequently precipitated in methanol. The highest efficiency of bioplastics production by Halomonas elongata BK-AB8 was around 24.7% using glucose as the main carbon resource. ¹H-NMR, ¹³C-NMR, and FTIR characterizations of the resulting bioplastic showed high similarities to the corresponding profiles of PHB, which is likely in the form of poly-(R)-hydroxybutyrate. Thermogravimetry Analysis (TGA) showed that the resulting PHB sample started to degrade at 210 °C. Further characterization by Differential Scanning Calorimetry (DSC) showed a melting temperature of PHB at 164 °C with a degree of crystallinity around 14.2%, which strongly indicates that PHB was successfully produced from Halomonas elongata BK-AB8.

Abstract: Vanillin is an additive widely used in foods and beverages. This research focused on formation of inclusion complexes to improve the stability of vanillin. The amylose in starch can act as a host molecule by forming a single helix known as V-amylose which has a hydrophobic channel. In this research, the starch was suspended in water (2.8% (w/v)) and was sonicated for 30 minutes. The mixture was subsequently heated at 180 °C to dissolve starch. Vanillin dissolved in ethanol was then mixed with the starch solution at around 85 °C. The concentration of vanillin was varied at 10%, 30% and 50% (w/w, based on the weight of starch). The resulting inclusion complexes were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and Scanning Electron Microscope (SEM). FTIR characterizations were conducted on starch, vanillin, physical mixture of starch-vanillin, and the inclusion complexes. The results showed there were differences on some vibration peaks between the physical mixture of starch-vanillin and the inclusion complex. The XRD results depicted different patterns of the diffraction peaks for the inclusion complexes compared to native starch and vanillin which showed that the starch-vanillin complexes were successfully formed.

Abstract: The research was conducted to investigate the oil and fatty acids contained in Tamarindus indica Linn (tamarind) seeds oil. Tamarind seeds oil was isolated by extraction and fractionation. The fatty acids content in oil were identified as fatty acid methyl ester. Fatty acid methyl ester was produced from trans-esterification reaction of tamarind seed oil with methanol and boron trifluoride catalyst (MeOH/BF₃). Identification of fatty acid methyl ester was carried out by gas chromatograph mass spectrometry (GC-MS). The fatty acids in the Tamarindus indica seed oil are saturated and unsaturated fatty acids. The saturated fatty acids are octanoic (12.66%), decanoic (1.68%), dodecanoic (25.18%), tetradecanoic (5.17-7.83%), hexadecanoic (9.90-16.06%), octadecanoic (3.82-4.80%), eicosanoic (0.39-1.55%), docosanoic (1.00-2.01%), and tetracosanoic (1.92-4.54%) acids. The unsaturated fatty acids are 11-octadecenoic (19.93%), 11-eicosenoic (0.76-1.03%), 9,12-octadecadienoic (21.91-38.68%), and 9-octadecenoic (17.76%) acids. The physical and antibacterial properties of the seed oil are also reported.

Abstract: Two imine derivative ligands, L1 and L2, have been synthesized using the microwave assisted organic synthesis (MAOS) method from the reaction between bibenzoyl and L-tryptophan and L-Histidine, respectively. The ligands were further transformed into two nickel(II) complex, C1 and C2, as the precursors of catalysts in glucose conversion to sorbitol. The two NiO/SiO₂ catalysts, K1 and K2, have been generated through the calcination process of complex C1 and C2, respectively, which were previously impregnated into silica. The K1 catalyst with average particle size of 5 nm shows good catalytic activity, with no presence of any nickel leached into the solution, and has successfully converted 21.99% of glucose into sorbitol. The K2 catalyst with average particle size of 10 nm also shows good catalytic activity and has successfully converted 32.30% of glucose into sorbitol, although it shows the presence of leached nickel.

Abstract: Wettability is one factor that influences the enhanced oil recovery. Water-wet surfaces are predicted increasing the oil recovery from the reservoir. Microcellulose has the potential to produce water-wet surfaces. In this experiment, two types of microcellulose were used with different particle sizes of 2.9 μm and 14 μm. Both types of microcellulose are then applied to the reservoir rock surface model, i.e the surface of bentonite which has been soaked in crude oil for one week at 60 °C. Contact angle measurement shows that there is a decrease in water-the reservoir rock surface model contact angle from ~ 90 ° to ~ 80 ° when applied microcellulose solution 0.5% w/w. The difference in microcellulose size causes a difference in contact angle of about 5° at microcellulose solution 2.5%. This shows the application of microcellulose on the reservoir rock surface model causing the surface to be more water-wet.