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.

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.

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.