| 1. |
- Almeida, Tiago P., et al.
(författare)
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Ultra-Thin Films of Reduced Graphene Oxide (RGO) Nanoplatelets Functionalized with Different Organic Materials
- 2016
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Ingår i: Journal of Bioprocessing & Biotechniques. - : OMICS Publishing Group. - 2155-9821. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- This work aims the functionalization of reduced graphene oxide nanoplatelets with chitosan (G-chitosan) and also with poly(styrenesulfonic acid) (GPSS), thus forming stable, dispersed aqueous solutions. G-chitosan and GPSS solutions allowed the layer-by-layer (LbL) film formation with glucose oxidase (GOx), establishing multilayered nanostructures with elevated control in thickness and morphology. The graphene nanoplatelets were characterized by UV-vis and FTIR spectroscopies, resulting in good adherence and linear deposition of the graphene nanoplatelets with GOx in the LbL structures.Cyclic voltammetry shows an enlargement in the current intensity with increasing number of deposited LbL layers, possibly owing to the formation of conducting paths by the graphene nanoplatelets in the tailored multilayer nanomaterial formed
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| 2. |
- Anderson, Mattias
(författare)
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Amine Transaminases in Multi-Step One-Pot Reactions
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Amine transaminases are enzymes that catalyze the mild and selective formation of primary amines, which are useful building blocks for biologically active compounds and natural products. In order to make the production of these kinds of compounds more efficient from both a practical and an environmental point of view, amine transaminases were incorporated into multi-step one-pot reactions. With this kind of methodology there is no need for isolation of intermediates, and thus unnecessary work-up steps can be omitted and formation of waste is prevented. Amine transaminases were successfully combined with other enzymes for multi-step synthesis of valuable products: With ketoreductases all four diastereomers of a 1,3-amino alcohol could be obtained, and the use of a lipase allowed for the synthesis of natural products in the form of capsaicinoids. Amine transaminases were also successfully combined with metal catalysts based on palladium or copper. This methodology allowed for the amination of alcohols and the synthesis of chiral amines such as the pharmaceutical compound Rivastigmine. These examples show that the use of amine transaminases in multi-step one-pot reactions is possible, and hopefully this concept can be further developed and applied to make industrial processes more sustainable and efficient in the future.
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| 3. |
- Bisagni, Serena, et al.
(författare)
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Exploring the Substrate Specificity and Enantioselectivity of a Baeyer-Villiger Monooxygenase from Dietzia sp D5: Oxidation of Sulfides and Aldehydes
- 2014
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 57:5, s. 366-375
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Tidskriftsartikel (refereegranskat)abstract
- Baeyer-Villiger monooxygenases (BVMOs) are valuable enzymes for specific oxyfunctionalization chemistry. They catalyze the oxidation of ketones to esters, but are also capable of oxidizing other chemical functions, namely aldehydes and heteroatoms such as sulfur, nitrogen, selenium and boron. The oxidation specificity and enantioselectivity of a newly characterized BVMO (BVMO4) from a strain of Dietzia towards sulfide- and aldehyde substrates have been studied. BVMO4 could react with sulfides containing an aromatic group. The presence of a substituent on the aromatic group was tolerated when they were in the meta- and para position and the oxidations yielded predominantly the (R)-sulfoxides. Similarly, BVMO4 displayed a higher activity for aldehydes containing a phenyl group, but long aliphatic aldehydes, namely octanal and decanal, were also accepted as substrate by this enzyme. The major oxidation products of the aldehyde substrates were the respective carboxylic acids in contrast to formate ester that was obtained in most of the previous reports. The Baeyer-Villiger oxidation of the substrate 2-phenylpropionaldehyde was studied in further detail and the corresponding acid product was obtained with good regio- and enantioselectivity. This is a unique feature for BVMO4 and is of great interest for further exploration of an alternative biocatalytic process.
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| 4. |
- Bornadel, Amin, et al.
(författare)
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A Bi-enzymatic Convergent Cascade for epsilon-Caprolactone Synthesis Employing 1,6-Hexanediol as a "Double-Smart Cosubstrate'
- 2015
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880. ; 7:16, s. 2442-2445
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Tidskriftsartikel (refereegranskat)abstract
- A bi-enzymatic cascade consisting of a Baeyer-Villiger monooxygenase and an alcohol dehydrogenase (ADH) was designed in a convergent fashion to utilise two molar equivalents of cyclohexanone (CHO) and one equivalent of 1,6-hexanediol as a 'double-smart cosubstrate' to produce epsilon-caprolactone (ECL) with water as sole by-product. The convergent enzymatic cascade reaction reported herein, is performed at ambient conditions in water, is self-sufficient with respect to cofactor, and incorporates all starting materials into the desired product, ECL. Among different enzymes explored, the reaction catalysed by cyclohexanone monooxygenase from Acinetobacter sp. NCIMB 9871 coupled with ADH from Thermoanaerobacter ethanolicus showed the best results, reaching 91% conversion of CHO after 24h with a product titre of 2gL(-1). Scale-up of the coupled system (50mL) performed better than the small-scale reactions and >99% conversion of CHO and ECL concentration of 20mM were achieved within 18h.
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| 5. |
- Bornadel, Amin, et al.
(författare)
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Enhancing the productivity of the bi-enzymatic convergent cascade for ɛ-caprolactone synthesis through design of experiments and a biphasic system
- 2016
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020. ; 72:46, s. 7222-7228
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Tidskriftsartikel (refereegranskat)abstract
- A two-step Design of Experiments (DoE) strategy followed by a two-liquid-phase system (2LPS) was applied to enhance the ɛ-caprolactone yield in the cyclohexanone monooxygenase (CHMO)-alcohol dehydrogenase (ADH) convergent cascade system. The key reaction parameters were identified and optimized for the determination of an optimal operational window for the aqueous media. In the 2LPS system, high partitioning of the lactone product was observed in 2-MeTHF and in toluene; however, these solvents led to drastically reduced enzymatic activity. Dodecane was chosen as the non-miscible organic phase owing to the enzymes’ high residual activity, despite the low partitioning of the lactone. Cyclohexanone concentrations up to 75 mM were applied in the aqueous media. The turnover numbers for the nicotinamide cofactor and for the ADH reached up to 980 and 392,000, respectively whereas a turnover number value of 5600 was achieved for the CHMO. By employing a 2LPS, whereby 91 mM of cyclohexanone was applied in the second phase, turnover numbers were slightly increased.
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| 6. |
- Görbe, Tamás, 1988-
(författare)
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Heterogeneous catalysis in racemization and kinetic resolution along a journey in protein engineering
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The first part of my thesis concerns the use of heterogeneous acidic resins for racemization of tert-alcohols without any side-product formation. The focus was to develop a system which can be further extended to a DKR protocol consisting of an enzymatic KR reaction. Based on our knowledge of the resins, an unexpected migratory DKR protocol turned out to be an efficient method for the synthesis of carbocyclic allylic carbinols.The development of enzyme and metal catalyst hybrids was already an ongoing theme in our group. A supporter-free biohybrid catalyst was developed which can be used in several different types of reactions. The Pd(0)-CalB CLEA catalyst was applied in a two-step-cascade transformation and in the DKR of benzylic primary amines. The catalyst was characterized by different analytical techniques, to understand its composition and structure.The enzymes have always been the main focus of the studies and therefore wild type enzymes were initially utilized. However, these natural biocatalysts are associated with certain limitations. In contrast, protein engineering allows for enzymes to be modified and optimized. We have used the technique to create a subtilisin Carlsberg mutant, which was studied both by modeling and in vitro. The mutant was found to catalyze the (S)-selective transesterification of sec-alcohols containing long aliphatic carbon chains, and it also exhibited higher performance in organic solvent.The last project concerned the protein engineering of CalA enzyme towards tert-alcohols. The kinetic resolution of tert-alcohols with this enzyme is very slow but it occurs with good enantioselectivity. The aim was therefore to improve the activity of CalA via protein engineering. Seven amino acids were mutated close to the active site and a library was created based on our prediction. Throughout the screening, a few variants showed higher activity, which were sequenced and further analyzed in the transesterification of tert-alcohols.
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| 7. |
- Morshed, Mohammad Neaz, Mr. 1992-
(författare)
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Immobilizing catalysts on textiles : case of zerovalent iron and glucose oxidase enzyme
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Catalytic systems are one of the most effective technologies of modern chemical processes. The system uses a molecule called ‘catalyst’ that is capable of catalyzing a reaction without being produced or consumed during the process. A catalytic system requires the separation of catalysts from products after each cycle, which is an expensive and resource-intensive process. This brought to the relevance of immobilization of catalyst, where catalysts are bind to a solid support material that will ensure the easy separation of catalyst. Immobilized catalysts are reusable and usually show better stability than the free catalyst. However, immobilization of catalyst is challenging, as it requires exclusive support material involving a complex preparation process. In many instances, the preparation of support material is more resource-intensive and expensive than the catalyst themselves. Therefore, this doctoral thesis focused on the innovative concept of using textile as reliable, widely accessible, and versatile support material for catalyst immobilization. Evidence from systematic experiments was gathered for the case of immobilization of an inorganic catalyst (zerovalent iron-Fe0) and a biocatalyst (glucose oxidase -GOx) on textile support. The goal of this thesis is to establish the feasibility of textile as support material for immobilization of catalyst in the pursuit of fabrication of heterogeneous catalytic system (oxidative and reductive) for wastewater treatment. Polyester nonwoven fabric (PF) was chosen as textile support material for catalyst immobilization due to both qualitative (high strength, porosity, biocompatibility and resistance to most acids, oxidizing agents, and microorganisms) and commercial (availability, cheap and easily customizable) advantages. A combination of eco-friendly and resource-efficient processes (such as plasma treatment, hyperbranched dendrimer, bio-based polymers) has been used for tailoring the PF surface with favorable surface chemical properties in the view of high and stable immobilization yield of the catalyst.The thesis has three distinct parts related to immobilizing catalyst on textiles- (a) immobilization of Fe0 on PF and optimizing their feasibility in both oxidative and reductive catalytic system; (b) immobilization of GOx on PF and optimizing their use in a bio-catalytic system; (c) design of the complete heterogeneous bio-Fenton system using immobilized catalysts (Fe0 and GOx). In all parts, the hydrophobic surface of PF was activated by plasma ecotechnology (either air atmospheric -AP or cold removal plasma-CRP) followed by chemical grafting of hyperbranched dendrimers (polyethylene glycol-OH or polyamidoamine ethylene-diamine core) or functional polymers (3-aminopropyl-triethoxysilane, polyethylenimine, chitosan, or 1-thioglycerol) before immobilizing either of two catalysts. The immobilization of Fe0 was carried out through either the in-situ or ex-situ reduction-immobilization method, whereas GOx was immobilized through the physical adsorption method. Several approaches were explored in search of optimum conditions for catalyst immobilization as well as to improve the catalytic performance of immobilized catalysts.Diverse analytical and instrumental techniques were used to monitor the surface modification of textiles, efficiency of immobilization of catalysts, Physico-chemical properties of immobilized catalysts, and their catalytic activities in the removal of dyes, phenols, or pathogenic pollutants from water. Results from plasma treatment showed that both AP and CRP successfully activated the PF surface through integrating polar functional groups (–COOH and –OH) by AP and carboxyl/hydroxyl (–COOH/–OH), amino (–NH2) functional groups by CRP. Along with that, grafted hyperbranched dendrimers and functional polymers on plasma-activated PF provided a tailor-made surface with specific end functional groups. Regarding the immobilization of Fe0 on PF, the results revealed that the reduction method (in-situ or ex-situ) of producing Fe0 have synergistic effects on the morphology, stability, particle size, and distribution of the immobilized Fe0. The surface chemical properties of PF also influenced the stability of immobilized Fe0 and related properties as observed throughout various studies. Detailed results revealed that a PF surface rich in –COOH, –OH, and –SH functional groups favors the loading and stabilization of Fe0 over surface rich in – NH2 functional groups. To end with, all Fe0-immobilized PF showed high catalytic activates in the removal of pollutants from water in both oxidative and reductive systems. In the case of GOx-immobilized PF, the success of immobilization of enzyme on textile was found to be related to the type and extent of surface functional groups present on the PF surface. The results demonstrated that PF surface rich in –COOH, – NH2 functional groups guaranteed higher loading and stability of GOx compared to –COOH, –OH functional groups-rich surface. These results carry great importance as they provide evidence of textile:enzyme interactions and grounds for further robust immobilization of GOx on textile support through surface engineering. As a proof of concept, this thesis also reveals the first successful design of a complete heterogeneous bio-Fenton system for wastewater treatment using immobilized catalysts (Fe0 and GOx). The novelty of the research presented in this doctoral thesis is primarily attributed to the novelty of immobilizing two different types of catalysts (inorganic catalyst and biocatalysts) on synthetic textile support for wastewater treatment application. In general, this thesis contributes to general knowledge of the heterogeneous catalytic system, Fenton/Fenton-like system, and the bio-Fenton system as well as it opens promising prospects of the use of textile as support material for immobilizing different catalysts for a wide range of applications.
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