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  • 1.
    Finnveden, Maja
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
    Semlitsch, Stefan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
    He, Oscar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
    Mono-substitution of symmetric diesters: selectivity of Mycobacterium smegmatis acyltransferase variants2019In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761Article in journal (Refereed)
    Abstract [en]

    A method for selectively reacting one, out of two identical carboxylic esters in a symmetric diester has been developed. An esterase from Mycobacterium smegmatis (MsAcT) has a restricted active site resulting in a narrow acyl donor specificity. This constraint was used to develop a selective synthesis route from divinyl adipate (a symmetric diester) towards mixed vinyl adipate esters. To find a suitable catalyst, the wild type (wt) MsAcT and two MsAcT variants: a single point mutant (L12A) and a double point mutant (T93A/F154A), were immobilized and studied under solvent-free conditions. Out of the tested catalysts, MsAcT L12A was the most selective for mono-transesterification of divinyl adipate. When divinyl adipate was reacted with 1.5 equivalents of a hydroxyl vinyl ether full conversion of DVA was observed yielding over 95% mixed diester. Furthermore, the limitations for longer dicarboxylic esters were studied, showing that MsAcT T93A/F154A tolerated up to at least dimethyl sebacate.

  • 2.
    Hendil-Forssell, Peter
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Engineering the esterase/acyltransferase from Mycobacterium smegmatis: extended substrate scope for amide synthesis in waterManuscript (preprint) (Other academic)
    Abstract [en]

    Some esterases/lipases display high acyl transfer activity, favoring alcoholysis over hydrolysis, which make them valuable catalysts for synthesis reactions in aqueous media. An esterase from Mycobacterium smegmatis, MsAcT, has been characterized as an efficient catalyst for ester synthesis in water. The acyl donor specificity for MsAcT was however found to be very narrow and the enzyme displayed no activity towards esters with larger acyl group than butyrate. With rational engineering, the narrow acyl donor specificity of wild type MsAcT enzyme was altered and variants displaying extended substrate scope were generated. A double mutant, T93A/F154A, could accommodate methyl nonanoate as substrate, i.e. five carbons longer acyl group as compared to wild type, without compromising the acyl transfer capabilities. With similar selectivity towards a broad range of acyl donors (propionate to nonanoate) this is a more applicable catalyst than the wild type. Furthermore, the T93A/F154A variant was an efficient catalyst for synthesis of N-benzylhexanamide in water using methyl hexanoate as acyl donor, which is not a substrate for the wild type enzyme. The conversion reached 81% and the enzyme variant could potentially be used to produce amides in water with a wide variety of acyl donors.

  • 3.
    Hendil-Forssell, Peter
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Rational engineering of an esterase/acyltransferase for improved amidase specificity in amide synthesis and hydrolysisManuscript (preprint) (Other academic)
    Abstract [en]

    The esterase/acyltransferase from Mycobacterium smegmatis, MsAcT, display high acyltransfer capacity in water media with demonstrations found for both ester and amide syntheses. However, it has recently been discovered that esterases in contrast to amidases lack a key hydrogen bond in the transition state, donated by the scissile NH-group of the substrate. Esterases with improved amidase performance have been achieved with the introduction of amino-acid side chains or water network as hydrogen bond acceptors. Using the esterase from Mycobacterium smegmatis, MsAcT, the influence of this hydrogen bond was studied in both amide hydrolysis and synthesis, using a rational engineering approach. Two positions were selected for mutagenesis and enzyme variants with improved performance in amide synthesis and hydrolysis were generated. Compared to the wild-type, variant F154A had the highest absolute increase in amidase specificity (11-fold) and I194Q had the greatest change in relative amidase versus esterase reaction specificity (160-fold). The relative reaction specificities for amide over ester synthesis followed a similar trend as that of hydrolysis and the best variant was I194Q with a 32-fold increase compared to wt. Based on MD-simulations water seems to play an important role in the transition state as a hydrogen bond bridge between the NH-group of the amide substrate and the enzyme.

  • 4.
    Nameer, Samer
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    One-pot enzyme-catalyzed synthesis of dual-functional polyester macromers towards surface active hydrophobic filmsManuscript (preprint) (Other academic)
    Abstract [en]

    Selective enzyme catalysis is a valuable tool for the processing of monomers into value-added materials. In the present study natural resources were used to retrieve an ω-hydroxy fatty acid monomer containing an epoxide functionality. A procedure was developed for the synthesis of dual-functional oligomers by utilizing lipase catalysis in a one-pot synthesis route. The chemoselectivity of the enzyme allowed addition of thiol monomers to the retrieved epoxy monomers, without harming the epoxides, achieving a thiol-epoxy functional polyester resin. The synthesis reached full conversion (>99 %) after 8 h. It was possible to selectively crosslink the resin, through UV-initiated cationic polymerization of the epoxides into thiol-functional thermosets. The curing performance was followed in situ by Real-Time FTIR. The thiol groups on the surface of the film were accessible for post-modification.

  • 5.
    Nameer, Samer
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    One-pot enzyme-catalyzed synthesis of dual-functional polyester macromers towards surface-active hydrophobic films2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 79, p. 50294-50299Article in journal (Refereed)
    Abstract [en]

    Selective enzyme catalysis is a valuable tool for the processing of monomers into value-added materials. In the present study natural resources were used to retrieve an omega-hydroxy fatty acid monomer containing an epoxide functionality. A procedure was developed for the synthesis of dual-functional oligomers by utilizing lipase catalysis in a one-pot synthesis route. The chemoselectivity of the enzyme allowed addition of thiol monomers to the retrieved epoxy monomers, without harming the epoxides, achieving a thiol-epoxy functional polyester resin. The synthesis reached full conversion (> 99%) after 8 h. It was possible to selectively crosslink the resin through UV-initiated cationic polymerization of the epoxides into thiol-functional thermosets. The curing performance was followed in situ by real-time FTIR. The thiol groups on the surface of the film were accessible for post-modification.

  • 6.
    Semlitsch, Bernhard
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Flow phenomena leading to surge in a centrifugal compressor2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 103, p. 572-587Article in journal (Refereed)
    Abstract [en]

    Surge is a global flow instability occurring in centrifugal compressors at low mass-flow rate operation. Due to its violent nature, it is the limiting factor for operability. To enhance the operating range, understanding of the flow instability inception when approaching surge is essential. Therefore, the flow evolution along a speed line is analysed by performing unsteady, three-dimensional flow simulations using a centrifugal compressor geometry with ported shroud. A stable operating condition, at high mass-flow rates, is compared to lower mass-flow rate operating conditions close to and at surge. The particularities of the flow-fields are analysed and described. A smooth flow-field is observed for the stable operating condition, whereas flow reversal manifesting as tip leakage at the outer periphery of the impeller occurs for all off-design operating conditions. The reversed flow exhibits swirling motion in the impeller rotation direction. This induces a globally swirling flow upstream of the impeller, which influences the flow incidence angles at the blades and hence, their efficiency. Proper orthogonal decomposition and dynamic mode decomposition have been performed to analyse the flow structures appearing with surge more thoroughly. For the lowest mass-flow rate operating condition, low frequency modes describing the filling and emptying processes during surge have been found.

  • 7.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Building blocks for polymer synthesis by enzymatic catalysis2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The search for alternatives to oil-based monomers has sparked interest for scientists to focus on the use of renewable resources for energy production, for the synthesis of polymeric materials and in other areas. With the use of renewable resources, scientists face new challenges to first isolate interesting molecules and then to process them.

    Enzymes are nature’s own powerful catalysts and display a variety of activities. They regulate important functions in life. They can also be used for chemical synthesis due to their efficiency, selectivity and mild reaction conditions. The selectivity of the enzyme allows specific reactions enabling the design of building blocks for polymers.

    In the work presented here, a lipase (Candida antarctica lipase B (CalB)) was used to produce building blocks for polymers. An efficient route was developed to selectively process epoxy-functional fatty acids into resins with a variety of functional groups (maleimide, oxetane, thiol, methacrylate). These oligoester structures, based on epoxy fatty acids from birch bark and vegetable oils, could be selectively cured to form thermosets with tailored properties.

    The specificity of an esterase with acyl transfer activity from Mycobacterium smegmatis (MsAcT) was altered by rational design. The produced variants increased the substrate scope and were then used to synthesize amides in water, where the wild type showed no conversion. A synthetic procedure was developed to form mixed dicarboxylic esters by selectively reacting only one side of divinyl adipate in order to introduce additional functional groups.

  • 8.
    Semlitsch, Stefan
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Mixed vinyl adipate esters through selective synthesis using a designed esterase/acyltransferaseManuscript (preprint) (Other academic)
    Abstract [en]

    Methods for selective syntheses of mixed dicarboxylic esters from symmetrical diesters are of great interest. An esterase from Mycobacterium smegmatis, MsAcT, has shown to be an efficient catalyst for acyl transfer reactions using both alcohols and amines. It has a restricted active site resulting in a narrow acyl donor specificity. This limitation was used for the development of a selective synthesis of mixed vinyl adipate esters from divinyl adipate. The single mutant, L12A, achieved over 90% conversion of divinyl adipate with three different alcohols leading to the corresponding mixed vinyl adipate esters. This method allows the synthesis of vinyladipoyl esters at mild reaction conditions.

  • 9.
    Semlitsch, Stefan
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Torron, Susana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Enzymatic catalysis as a versatile tool for the synthesis of multifunctional, bio-based oligoester resins2016In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 18, no 7, p. 1923-1929Article in journal (Refereed)
    Abstract [en]

    The use of enzymes as selective catalysts for processing renewable monomers into added value polymers and materials has received increased attention during the last decade. In the present work Candida antarctica lipase B (CalB) was used as catalyst in one-pot routes to synthesise multifunctional oligoester resins based on an epoxy-functional omega-hydroxy-fatty acid (EFA) extracted from birch bark. The chemoselective enzymatic process resulted in three different EFA-based telechelic oligomers with targeted molecular weights; containing maleimide, methacrylate or oxetane as end-groups, respectively. The enzyme catalysed synthesis of the maleimide and the oxetane telechelic oligomers reached full conversion of monomers (>95%) after 2 h. In the case of methacrylate functional oligomer the EFA monomer reached full conversion (>98%) after 2 h but the integration of the methacrylate moiety took more than 10 h. This was due to a rate limiting reaction path using ethylene glycol dimethacrylate as substrate. The oligomer products were characterised by NMR, MALDI-TOF-MS and SEC.

  • 10.
    Torron, Susana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinell, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Biocatalytic Synthesis of Epoxy Resins from Fatty Acids as a Versatile Route for the Formation of Polymer Thermosets with Tunable Properties2016In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 12, p. 4003-4010Article in journal (Refereed)
    Abstract [en]

    The work herein presented describes the synthesis and polymerization of series of bio-based epoxy resins prepared through lipase catalyzed transesterification. The epoxy-functional polyester resins with various architectures (linear, hi branched, and tetra-branched) were synthesized through condensation of fatty acids derived from epoxidized soybean oil and linseed oil with three different hydroxyl cores under bulk conditions. The selectivity of the lipases toward esterification/transesterification reactions allowed the formation of macromers with up to 12 epoxides in the backbone. The high degree of functionality of the resins resulted in polymer thermosets with T-g values ranging from 25 to over 100 degrees C prepared through cationic polymerization. The determining parameters of the synthesis and the mechanism for the formation of the species were determined through kinetic studies by H-1 NMR, SEC, and molecular modeling studies. The correlation between macromer structure and thermoset properties was studied through real-time FTIR measurements, DSC, and DMA.

  • 11.
    Torron, Susana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Semlitsch, Stefan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Polymer Thermosets from Multifunctional Polyester Resins Based on Renewable Monomers2014In: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 215, no 22, p. 2198-2206Article in journal (Refereed)
    Abstract [en]

    The use of monomers based on natural materials as a future supply of raw materials has gained more interest in the last decade. Sources ranging from wood to plant oils and algae are exploited as alternatives to traditional fossil-based resources for the synthesis of polymeric materials. The use of these raw materials is not only of interest because of its abundance, but also in terms of price, durability, and/or biodegradability. In the present study, a series of resins utilizing a monomer derived from birch bark is prepared. The thermoset resins are formed by reacting an epoxy-functional omega-hydroxy fatty acid with methacrylate monomers using enzyme catalysis to form multifunctional resins via a one-pot synthesis. The derived oligomers are crosslinked through different polymerization routes to produce thermosets with different properties and/or functionalities. This approach allows natural-based resins with tuned functionalities and mechanical and thermal properties to be obtained.

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