Yusof, Nurul Nadzirah Mohd (2018) Lipase-Catalyzed Synthesis Of Caffeic Acid Bornyl Ester. Masters thesis, Universiti Sains Malaysia.
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Abstract
Ester asid kaffeik bornil (EAKB) berasaskan asid kaffeik merupakan produk semulajadi yang jarang ditemui serta mempunyai sifat biologi dan farmakologi yang signifikan. Walaubagaimanapun, penggunaan cara tradisional seperti pengekstrakan dan sintesis menggunakan bahan kimia bagi menghasilkan sebatian ini memerlukan kos yang tinggi, kurang cekap dan toksik kepada manusia dan alam sekitar. Oleh itu, objektif utama kajian ini adalah untuk memperkenalkan tindak balas hijau bagi menghasilkan EAKB menggunakan enzim lipase sebagai pemangkin dalam tindak balas transesterifikasi. Sintesis EAKB telah dijalankan dengan melakukan pemeriksaan awal ke atas beberapa pemboleh ubah tindak balas penting seperti pelbagai jenis enzim disekat gerak (Novozym 435, Lipozyme TLIM and Lipozyme RMIM), pelarut organik (isooctane, n-hexane, n-heptane, toluene, acetone, acetonitrile, n-hexane:diethyl ether and n-hexane:acetone) dan jenis kumpulan alkil yang digunakan (metil kaffeat and etil kaffeat) diikuti dengan mengkaji kesan pemboleh ubah tindak balas seperti jumlah enzim (25 – 250 U), masa tindak balas (0 – 84 h), nisbah substrat borneol kepada etil kaffeat (1:1, 1.5:1, 2:1, 2.5:1 and 3:1), suhu tindak balas (30 - 60°C) dan keadaan tindak balas optimum menggunakan kaedah tradisional satu faktor dalam satu masa untuk mendapatkan respon tertinggi. Mekanisma kinetik telah dikaji dan pemalar kinetik telah ditentukan berdasarkan kadar tindak balas awal yang diperoleh daripada penyiasatan ke atas kesan kepekatan substrat. Pengoptimuman bagi penghasilan EAKB juga telah dijalankan dengan menggunakan kaedah tindak balas permukaan dengan reka bentuk “face-centered central composite design (CCD)” bagi mendapatkan respon tertinggi. Akhir sekali, tenaga pengaktifan yang diperlukan untuk tindak balas telah ditentukan dengan menjalankan tindak balas transesterifikasi pada pelbagai suhu dari 30°C sehingga 55°C. Hasil daripada pemeriksaan awal yang telah dijalankan, Novozym 435 telah didapati memberikan pertukaran tertinggi diikuti oleh enzim Lipozyme TLIM dan enzim Lipozyme RMIM. Pertukaran substrat tertinggi juga telah diperolehi dengan menggunakan sistem pelarut campuran (n-hexane:acetone, 80:20, % isipadu/isipadu) dan etil kaffeat sebagai substrat. Berdasarkan kajian ke atas pemboleh ubah tindak balas menggunakan kaedah satu faktor dalam satu masa, pertukaran tertinggi telah diperoleh dengan menggunakan unit enzim sebanyak 125 U dan masa tindak balas selama 48 jam pada suhu 55°C. Nisbah substrat borneol kepada etil kaffeat 2.5:1 (25 mM borneol: 10 mM EC) telah diperhatikan menghasilkan peratusan pertukaran tertinggi. Pada keadaan tindak balas optimum seperti yang telah dinyatakan di atas, peratusan pertukaran substrat tertinggi telah diperoleh iaitu sebanyak 86.0%. Model kinetik bagi tindak balas sintesis EAKB menggunakan enzim lipase Novozym 435 telah didapati mematuhi mekanisme kompleks ternari dan pemalar kinetik adalah seperti berikut; KmEC = 0.091 mM, KmBor = 10.908 mM, Vmax = 0.187 mM/min and KiBor = 1.943 mM. Keadaan optimum yang telah dicadangkan oleh kaedah tindak balas permukaan dengan rekabentuk “face-centered central composite design (CCD)” pula adalah menggunakan jumlah enzim sebanyak 245 U dalam tempoh selama 36 jam dan suhu 60°C untuk menghasilkan kadar pertukaran substrat optimum sebanyak 93.64%. Anggaran bagi tenaga pengaktifan yang diperlukan oleh lipase Novozym 435 untuk sintesis EAKB adalah 57.6 kJ/mol. _______________________________________________________________________________________________________ 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.
| Item Type: | Thesis (Masters) |
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| Additional Information: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=4730 |
| Subjects: | T Technology T Technology > TP Chemical Technology > TP1-1185 Chemical technology |
| Divisions: | Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraan Kimia (School of Chemical Engineering) > Thesis |
| Depositing User: | Mr Mohd Jasnizam Mohd Salleh |
| Date Deposited: | 19 Jun 2019 09:23 |
| Last Modified: | 19 Jun 2019 09:23 |
| URI: | http://eprints.usm.my/id/eprint/44677 |
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