Enzyme immobilisation technology is an effective means to improve sugar ester production through the employment of biocatalysts. In the present study, immobilisation of Candida rugosa (CRL) lipase onto amino-activated mica is performed via covalent bonding (namely Amino-CRL) and the cross-linking of lipases into nano-reactors through physical adsorption (namely NER-CRL). Free and immobilised lipases were tested for their esterification activities. Specific activities for Amino-CRL and NER-CRL increased by 2.4 and 2.6-fold, respectively, upon immobilisation. Extending this work, immobilised lipases have novel capabilities in the synthesis of sugar esters. The optimised conditions for sugar fatty acid ester syntheses are 48 h at 2:1 of molar ratio of lactose sugar to capric acid at 55 C. Furthermore, a high operational stability with half-lives of over 13 and 10 runs was achieved for NER-CRL and Amino-CRL, respectively, indicating the efficiency of the immobilisation process. (C) 2011 Elsevier Ltd. All rights reserved.

The utilization of natural mica as a biocatalyst support in kinetic investigations is first described in this study. The formation of lactose caprate from lactose sugar and capric acid, using free lipase (free-CRL) and lipase immobilized on nanoporous mica (NER-CRL) as a biocatalyst, was evaluated through a kinetic study. The apparent kinetic parameters, K-m and V-max, were determined by means of the Michaelis-Menten kinetic model. The Ping-Pong Bi-Bi mechanism with single substrate inhibition was adopted as it best explains the experimental findings. The kinetic results show lower K-m values with NER-CRL than with free-CRL, indicating the higher affinity of NER-CRL towards both substrates at the maximum reaction velocity V-max,V-app > V-max). The kinetic parameters deduced from this model were used to simulate reaction rate data which were in close agreement with the experimental values.

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.

BackgroundAlthough the development of antibiotic and antioxidant manufacturing, the problem of bacterial resistance and food and/or cosmetics oxidation still needs more efforts to design new derivatives which can help to minimize these troubles. Benzimidazo[1,2-c]quinazolines are nitrogen-rich heterocyclic compounds that possess many pharmaceutical properties such as antimicrobial, anticonvulsant, immunoenhancer, and anticancer.ResultsA comparative study between two methods, (microwave-assisted and conventional heating approaches), was performed to synthesise a new quinazoline derivative from 2-(2-aminophenyl)-1H-benzimidazole and octanal to produce 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline (OCT). The compound was characterised using FTIR, H-1 and C-13 NMR, DIMS, as well as X-ray crystallography. The most significant peak in the C-13 NMR spectrum is C-7 at 65.5ppm which confirms the cyclisation process. Crystal structure analysis revealed that the molecule grows in the monoclinic crystal system P2(1)/n space group and stabilised by an intermolecular hydrogen bond between the N1-H1A...N3 atoms. The crystal packing analysis showed that the molecule adopts zig-zag one dimensional chains. Fluorescence study of OCT revealed that it produces blue light when expose to UV-light and its' quantum yield equal to 26%. Antioxidant activity, which included DPPH and ABTS(+) assays was also performed and statistical analysis was achieved via a paired T-test using Minitab 16 software with P<0.05. Also, the antimicrobial assay against two Gram-positive, two Gram-negative, and one fungus was screened for these derivatives.ConclusionsUsing microwave to synthesise OCT have drastically reduced reaction time, and increased yield. OCT show good antioxidant activity in one of the tests and moderate antimicrobial activity.

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

Optically active (-)-menthyl butyrate was synthesized by enantioselective esterification of racemic (+/-)-menthol and butyric anhydride using lipase from Candida rugosa immobilized onto epoxy-activated supports of Eupergit C and Eupergit C 250 L through physical adsorption method. The effects of various temperature, storage condition, stability in organic solvent and lipase recyclability were investigated for their influence on the enzymatic enantio selective formation of (-)-menthyl butyrate. The immobilized lipases retained high catalytic activity of up to 31% yield and 100% enantiomeric excess of the desired product, and showed better stability compared to the native lipase. They also exhibited about 50% retained activity even after incubation at higher temperatures, storage at room temperature and after long incubation in hexane. Immobilized lipases also showed considerably efficient reusability. (C) 2007 Published by Elsevier Ltd.

Mica was modified either by acid treatment, grafting with aminopropyl-, octyl-, vinyl-, mercapto- and glycidoxy-triethoxysilanes, and activation of pre-treated support with glutaraldehyde (Glu). The derivatives were characterized by X-ray diffraction (XRD), infra-red spectroscopy (FTIR), surface area and porosity analysis, scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM) techniques. The modified micas were used for immobilization of lipase from Candida rugosa (CRL). Activity of the lipase was determined by esterification and exhibited the improved activity than the free enzyme following the order; Amino-CRL>Glu-Amino-CRL>Octyl-CRL>Vinyl-CRL>Glycidoxy-CRL>Mercapto-CRL>Mica-CRL Lipase immobilized mica showed enhanced protein loading (up to 8.22 mg protein/g support) and immobilization (up to 78%) compared to the free lipase and unmodified mica. (C) 2009 Elsevier B.V. All rights reserved.

New 6-substituted-5,6-dihydrobenzo[4,5] imidazo[1,2-c] quinazoline compounds were synthesized using two different protocols: microwave-enhanced and classical heating methods. A comparison study that was set up to compare both the methods and the results showed that the microwave-assisted method produced a better percentage yield (up to 98%) in a very short reaction time (only a few minutes). All compounds were characterized by spectroscopic and elemental analysis. Only one compound was analyzed by single crystal X-ray diffraction despite the difficulties of getting good crystal even after several attempts. The X-ray crystallography results were chemically acceptable and confirmed the structure of benzimidazoquinazoline 5. Incidentally, the studied derivatives were found to emit a very nice blue light when exposed to UV-light. Therefore, a photoluminescence study was performed as a part of the characterization processes. Biological application as an antimicrobial and an antioxidant for the target analogues was performed. Some derivatives exhibited high antibacterial activity against studied Gram-positive strains, although they were not active against Gram-negative strains. Moreover, some of them showed excellent antioxidant activities against both of the studied antioxidant DPPH center dot and ABTS(center dot)(+) radicals. (C) 2019 Elsevier B.V. All rights reserved.