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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorGross, Richard A.
dc.contributorBystroff, Christopher, 1960-
dc.contributorColón, Wilfredo
dc.contributorLinhardt, Robert J.
dc.contributorMakhatadze, George I.
dc.contributor.authorSu, An
dc.date.accessioned2021-11-03T09:00:41Z
dc.date.available2021-11-03T09:00:41Z
dc.date.created2018-07-27T15:10:04Z
dc.date.issued2018-05
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2207
dc.descriptionMay 2018
dc.descriptionSchool of Science
dc.description.abstractChapter 4 summarizes the major findings of this dissertation and points out several interesting perspectives for future research. Advanced immobilization techniques can be applied to the immobilization of cutinases to achieve a higher enzyme thermostability. Meanwhile, the effect of the parameters of immobilization matrices (e.g. pore size, surface area, and functional group) can be studied to deeply understand the mechanism of cutinase immobilization. On the other hand, substrates that are more sterically hindered (e.g. cyclohexanol derivatives) can be tested to see if cutinases still have higher conversion rates while maintaining the enantioselectivity.
dc.description.abstractEnantioselectivity is an extremely important function of catalysts, especially for pharmaceutical industry. Many lipases have been studied in the kinetic resolution reactions producing enantiopure compounds, but similar studies on cutinases are still in the early stage. In Chapter 3, the enantioselectivity and activity of two cutinases, AoC and HiC, was tested on the transesterification of 1-phenylethanol and its related compounds with vinyl acetate, and the results are compared to those of a benchmark lipase, Novozym 435, a commercial immobilized lipase known as Lipase B from Candida antarctica (CALB). Both cutinases are found to be selective to (R)-enantiomers as CALB and other classic lipases are. However, AoC not only shows a higher activity in most of the phenyl alcohols but also shows a significant better accommodation to medium substituent larger than an ethyl group compared to the other two enzymes. Based on previous researches on the structure of lipases and cutinases as well as substrate docking studies, the larger size of stereospecific binding pocket may be the reason that AoC shows a higher activity in the secondary alcohols with a more sterically hindered M-substituent. Computer modeling researches are underway to confirm this conclusion.
dc.description.abstractIn Chapter 2, immobilization studies were performed with three well-characterized cutinases (Aspergillus oryzae Cutinase (AoC), Humicola insolens Cutinase (HiC), and Thielavia terrestris Cutinase (TtC)) using Lewatit VP OC 1600 as the macroporous support. We found that loading efficiencies >98% were achieved for all three cutinases under the following immobilization conditions: 10% loading ratio, 100mM phosphate (AoC and HiC) or acetate (TtC) buffer concentration, mixing at 150 r.p.m. and 30°C for 24 h. Among the three cutinases, HiC has the highest tolerance towards solvents of increased polarity while TtC has the highest thermal stability (up to 80°C) in a bulk reaction system that consists of the reactants butanol and lauric acid. In nonane, these cutinases retain relatively high activity at 90°C. Furthermore, they have high kinetic stability at 70°C while TtC has higher kinetic stability than HiC and AoC at 80°C. Collectively, the results herein set the stage for the in-depth evaluation of these catalysts for selective transformations in organic media.
dc.description.abstractChapter 1 serves as an introduction to cutinase, especially its application in biocatalysis. The important previous researches on the preparation of cutinases as catalysts and the reactions cutinase can catalyze in aqueous solution and organic media are summarized. The objectives of this dissertation are also listed.
dc.description.abstractCutinase is an α/β hydrolase with a Ser-His-Asp catalytic triad that has been known to hydrolyze cutin as well as a variety of polyester and polyamides. Cutinase has been considered as a bridge between esterase and lipase because of its ability to catalyze in solution as well as in lipid phase. However, studies of cutinase in organic media are many fewer than those of lipase and esterase though an increasing number of cutinases are being discovered and characterized. Hence, this dissertation will focus on preparing cutinase as biocatalysts in organic media, characterizing the catalysts’ solvent tolerance and thermostability, and studying its structure-function relationship in enantioselective transesterifications.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectChemistry
dc.titleCutinase in organic media : preparing immobilized cutinase, studies of catalyst solvent tolerance, thermal stability, and structure-function relationship in enantioselective transesterifications
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid179028
dc.digitool.pid179029
dc.digitool.pid179030
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Chemistry and Chemical Biology


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