Lipase-catalyzed synthesis of caffeic acid bornyl ester
| dc.contributor.author | Nurul Nadzirah Mohd Yusof | |
| dc.date.accessioned | 2021-11-02T07:51:25Z | |
| dc.date.available | 2021-11-02T07:51:25Z | |
| dc.date.issued | 2018-07-01 | |
| dc.description.abstract | Caffeic acid bornyl ester (CABE) is a rare caffeic acid derivative and natural product with significant biological and pharmacological properties. However, the use of traditional chemical extraction and chemical synthesis method to produce CABE are uneconomical, inefficient and toxic to human and environment. Thus, the main objective of this study is to establish a green reaction pathway for the synthesis of CABE via lipase-catalyzed transesterification reaction. The synthesis of CABE was conducted by the screening of important parameters such as types of immobilized enzyme (Novozym 435, Lipozyme TLIM and Lipozyme RMIM), organic solvents (isooctane, n-hexane, n-heptane, toluene and n-hexane:acetone) and effect of alkyl group (methyl caffeate and ethyl caffeate) followed by investigating the effect of reaction parameters such as enzyme loading (25 – 250 U), reaction time (0 – 84 h), substrate ratio of borneol to ethyl caffeate (1:1, 1.5:1, 2:1, 2.5:1 and 3:1), reaction temperature (30 – 60°C) and optimum reaction conditions based on traditional one factor at a time (OFAT) method. The reaction kinetic mechanism was investigated and kinetic parameters of lipase-catalyzed transesterification reaction were determined based on the initial reaction rate obtained from the investigation of the effect of substrates concentration. The optimization of CABE production was also conducted using response surface methodology (RSM) based on face-centered central composite design (CCD) to obtain the highest response. Finally, the activation energy required for the reaction was determined by conducting the transesterification reaction at various temperatures from 30°C to 55°C. From the screening, it was found that Novozym 435 gave the highest conversion followed by Lipozyme TLIM and Lipozyme RMIM. The highest substrate conversion was obtained using mixed solvents system (n-hexane:acetone, 80:20, %v/v) and ethyl caffeate as substrate. In the investigation of effect of reaction parameters based on OFAT method, the highest conversions were obtained by using 125 U of enzyme loading, 48 h of reaction time and temperature at 55°C. It was observed that the substrate ratio of borneol to EC, 2.5:1 (25 mM borneol: 10 mM EC) resulted in the highest conversion. At the selected optimum reaction conditions as described above, the highest substrate conversion of 86.0% was obtained. The reaction kinetics model for CABE synthesis using lipase Novozym 435 was found to obey the ternary complex mechanism and the kinetic parameters were as follows; KmEC = 0.091 mM, KmBor = 10.908 mM, Vmax = 0.187 mM/min and KiBor = 1.943 mM. The optimized condition suggested by RSM was found to be 245 U of enzyme loading at 36 h and 60°C with 93.64% conversion. The estimated activation energy value of lipase Novozym 435 for the synthesis of CABE was observed to be 57.6 kJ/mol. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/14333 | |
| dc.language.iso | en | en_US |
| dc.title | Lipase-catalyzed synthesis of caffeic acid bornyl ester | en_US |
| dc.type | Thesis | en_US |
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