Clay catalyst has received much attention to replace the homogeneous catalysts in the esterification reaction to produce fatty acid methyl ester as the source of biodiesel as it is low cost, easily available, as well as environmental friendly. However, the use of unmodified clay, in particular montmorillonite K10 (MMT K10), for the esterification of fatty acids showed that the acid conversion was less than 60% and this is not preferable to the production of biodiesel. In this study, synthesis of stearic acid methyl ester using Cu2+-MMT K10 (Cu-MMT K10) was successfully optimized via response surface methodology (RSM) based on 3-variable of Box-Behnken design (BB). The parameters were; reaction time (5180 minutes), reaction temperature (80-120 degrees C) and concentration of Cu2+ in MMT K10 (0.25-1 M). The use of RSM in optimizing the conversion of stearic acid was successfully developed as the actual experimental conversion of stearic acid was found similar to the actual values under the optimum conditions. The model equation predicted that the following conditions would generate the maximum conversion of stearic acid (87.05 % reaction time of 62 minutes, a reaction temperature of 80 degrees C and catalyst used is 1.0 M Cu-MMT K10. This finding can be considered as green catalytic process as it worked at moderate reaction temperature using low cost clay catalyst with a short reaction time. Copyright (C) 2018 BCREC Group. All rights reserved.

This paper focuses on the effect of lithium triflate (LiCF3SO3) on the structural and conduction properties of lauroyl (L)-chitosan/poly(metylmethacryalate) (PMMA)-based polymer electrolytes. Films of L-chitosan/PMMA blends and its complexes were prepared using a solution-casting technique. The ionic conductivity of the system was measured over a wide range of frequency between 50Hz-1MHz. Impedance plot for the samples demonstrates two well-defined regions. The disappearance of the high frequency semicircular region led to a conclusion that the current carriers are ions. Sample with 30 wt% of LiCF3SO3 showed the highest conductivity of 7.59 +/- 3.64 x 10(-4) Scm(-1) at room temperature. This is consistent with the results obtained from infrared spectroscopy.

Enzymatic synthesis of kojic ester, a bio-based whitening agent, was successfully carried out via esterification reaction between oleic acid and kojic acid. Commercial immobilized lipases of Novozym 435 and Lipozyme RIM FM were used in combination as biocatalyst in the reaction system. Various reaction parameters were chosen to optimize the reaction in order to obtain a high yield of kojic ester including the best ratio of lipases, reaction time and reaction temperature. The optimum conditions for the synthesis of kojic ester was achieved at reaction time of 12 hours, temperature of 60 degrees C and equal ratio of lipases to produce more than 70 % yield. Antimicrobial tests of synthesized kojic ester towards several types of bacteria via Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) analyses were also examined. The results obtained suggested that kojic ester exhibits a good bactericidal effect towards all bacteria tested such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium.

The kinetics of wax ester synthesis from oleic acid and oleyl alcohol using immobilized lipase from Candida antartica as catalyst was studied with different types of impeller (Rushton turbine and AL-hydrofoil) to create different mixing conditions in 21 stirred tank reactor. The effects of catalyst concentration, reaction temperature, and impeller tip speed on the synthesis were also evaluated. Rushton turbine impeller exhibited highest conversion rate at lower impeller tip speed as compared to AL-hydrofoil impeller. A second-order reversible kinetic model from single progress curve for the prediction of fractional conversion at given reaction time was proposed and the corresponding kinetic parameter values were calculated by non-linear regression method. The results from the simulation using the proposed model showed satisfactory agreement with the experimental data. Activation energy shows a value of 21.77 Kcal/mol. The thermodynamic parameters of the process, enthalpy and entropy, were 21.15 Kcal/mol and 52.07 cal/mol.K, respectively.

BACKGROUND: Adipate esters are used as low-temperature and low-viscosity plasticizers for polyvinyl chloride and its copolymers. In this work, optimization of lipase-catalyzed production of dilauryl adipate was carried out using response surface methodology (RSM) based on a four-factor-five-level central composite rotatable design (CCRD). Immobilized lipase from Candida antarctica (Novozym 435) was used as catalyst in this reaction. Various reaction parameters affecting the synthesis of adipate ester, including alcohol/acid molar ratio, amount of enzyme, temperature and reaction time, were investigated. RESULTS: Statistical analysis showed that the amount of enzyme was less significant than the other three factors. The optimal conditions for the enzymatic reaction were obtained at 5.7:1 substrate molar ratio using 0.18g of enzyme at 53.1 degrees C for 282.2 min. Under these conditions the esterification percentage was 96.0%. CONCLUSIONS: The results demonstrated that response surface methodology can be applied effectively to optimize the lipase-catalyzed synthesis of adipate ester. The optimum conditions can obtained be used to scale up the process. (C) 2008 Society of Chemical Industry

Pharmacodynamic research plays an important role in the development of new antibacterial agents. Characterization of this pharmacodynamic can be used to design the best dose and dosing strategy for clinical trials. The pharmacodynamic properties can be determined by studying the bactericidal activity and the postantibiotic effects (PAE). Measurements of both bactericidal activity and the lag time could be useful in screening the efficacy of antimicrobial agents. In this study, the pharmacodynamic properties of essential oils from Cymbopogon flexuosus (lemongrass) and Cymbopogon nardus (citronella) as well as the combinations of both essential oils were evaluated against Staphylococcus aureus and Escherichia coli. At high concentrations (1.0 x minimum bactericidal concentration (MBC) and 0.5 x MBC), citronella and lemongrass essential oils alone or in combinations indicate high bactericidal activities toward S. aureus and E. coli, as shown by the decrease of optical absorbance values serially up to 24 h. However, these two essential oils or its combinations at lower concentrations (0.25 x MBC and 0.125 x MBC) showed the bacterial regrowth after 3 and 1 h of exposure time against S. aureus and E. Coli, respectively. Generally, citronella and lemongrass essential oils as well as its combinations indicate a significant lag of regrowth or PAE values which were more than 0.5 h towards both E. coli and S. aureus. This finding suggests that essential oils from Cymbopogon species showed a potential antimicrobial activity that can further be used for clinical treatment; thus, there is need for a study on the possible impact of PAE in the clinical situation.

Kojic acid is an organic acid that widely used in cosmetic, health care, food and chemical industries. However, kojic acid is not stable at high temperature, for long storage and it has low lipophilic properties. To overcome this problem, a study was conducted to improve its properties by enzymatic reaction. This study was focused on the synthesis of kojic acid monooleate from kojic acid and oleic acid using enzymatic catalysts at optimized conditions. This study was divided into three parts starting from enzymatic synthesis of kojic ester or specifically kojic acid monooleate (KAMO) by using a dual enzymes system that consisted of Novozym 435 and Lipozyme RM IM. Then, optimization of four variables such as screening of dual enzymes ratio, temperature, substrate molar ratio and the reaction time via conventional method of one parameter at-a-time approach and lastly verification of the product using Fourier Transfer Infrared (FTIR) spectroscopy. The optimum conditions for the enzymatic synthesis of KAMO were at the dual enzymes ratio (1: 1) of Novozym 435 and Lipozyme RMIM, temperature at 50 degrees C, the molar ratio of kojic acid and oleic acid were 4: 1 respectively and 24 hours of reaction time. The highest percentage conversion of KAMO achieved at the most optimum conditions was 13.22 %. Finally, kojic ester produced was verified by using FTIR proved the presence of ester bond (C=O) at 1743 cm(-1).