A dissertation submitted in fulfilment of the requirements for the degree Master of Science
in Molecular and Cell Biology in the Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa, 2019 / Biocatalysis is the use of biological systems, such as enzymes, to perform chemical transformations on organic compounds. These enzymes catalyse reactions as whole cell systems or in isolated forms and have been found to exhibit high regio- and stereoselectivity towards chiral compounds. Lipases have been extensively used to catalyse kinetic resolutions of chiral compounds such as the Morita-Baylis-Hillman (MBH) adducts. The MBH adducts and their esters are important intermediates in organic synthesis and have been found to be valuable in the production of biologically active compounds. In this study, we expressed and partially purified the Pseudomonas fluorescens P26504 lipase in an active and soluble form to catalyse the kinetic resolution on MBH acetates to obtain enantiopure MBH adducts. The Pseudomonas fluorescens P26504 lipase was overexpressed in BL21 (DE3) pLysS cells at 25 °C for 16 hours, with 1mM IPTG concentration. Enzymatic assays were conducted after partial purification using p-nitrophenyl esters. The recombinant enzyme was highly active towards short chain esters and showed moderate activity towards medium chained esters. The Morita-Baylis-Hillman reaction was conducted, giving rise to racemic MBH adducts derived from benzaldehyde and hydro-cinnamaldehyde. The second step of the reaction was acetylation, producing chiral MBH acetates. A lipase-catalysed kinetic resolution was set-up, using the partially purified recombinant P. fluorescens P26504 lipase and the MBH acetates. TLC plate analysis showed that the recombinant lipase was able to hydrolyse both MBH acetates. However, further studies can be done to determine the enantioselectivity of the recombinant P. fluorescens P26504 lipase using chiral HPLC, which is more definitive. / TL (2020)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/29664 |
| Date | January 2019 |
| Creators | Mguni, Lindelo Mthabisi |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (65 leaves), application/pdf |
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