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.

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.

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.