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Item type:Publication, Access status: with files , Evaluation of deep eutectic solvents as alternative reaction media in biocatalysisEnzyme catalysis is often associated with aqueous reaction media, but water is rather an inadequate solvent for hydrophobic substrates. In this study ‘deep eutectic solvents’ (DESs) were evaluated as novel reaction media for biocataylsis. For instance, a DES composed of both substrates, i.e. a DES made of (–)-Menthol:lauric acid, was used as combined solvent and substrate for the lipase catalysed synthesis of (–)-menthyl laurate, so that no additional solvent was necessary. The optimisation of the reaction resulted in a batch productivity of 443 g L−1 d−1 at 95 % conversion (24 h). Excess (–)-menthol was separated in a vacuum distillation step and was reused for a second enzymatic DES reaction.Publicationtype: Doctoral Thesis328 582 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Deep Eutectic Solvents as Efficient Solvents in Biocatalysis‘Ideal’ solvents in biocatalysis have to fulfill a large number of requirements, such as high substrate solubility, high enzyme activity and stability, and positive effects on reaction equilibrium. In the past decades, many enzymatic synthesis routes in water-based and nonaqueous (organic solvents, ionic or supercritical fluids) reaction media have been developed. However, no solvent meets every demand for different reaction types at the same time, and there is still a need for novel solvents suited for different reaction types and applications. Deep eutectic solvents (DESs) have recently been evaluated as solvents in different biocatalytic reactions. They can improve substrate supply, conversion, and stability. The best results were obtained when the DES is formed by the substrates of an enzymatic reaction.Publicationtype: Journal Article359 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Product recovery of an enzymatically synthesized (−)-menthol ester in a deep eutectic solvent(2019-08-01); ; ; ; Deep eutectic solvents (DESs) have gained increased attention as alternative reaction media for biocatalysis in recent years. There are many investigations on biotransformations in a variety of DESs, but the purification of bioproducts from DES reaction mixtures has not yet been sufficiently addressed. The present study demonstrates a product recovery strategy from a DES reaction medium composed of (−)-menthol and dodecanoic acid. Since the DES is not formed by equimolar amounts of the substrates, but the eutectic point occurs at a 3:1 molar ratio, product isolation is an important task for effective biocatalytic process development, even if the limiting substrate is converted completely. Both DES compounds acted as substrates and reaction solvent in the lipase-catalyzed esterification to synthesize (−)-menthyl dodecanoate. The product (−)-menthyl dodecanoate ester was separated from the DES reaction mixture by a vacuum distillation step and a second esterification reaction can be performed with the recovered (−)-menthol.Publicationtype: Journal ArticleScopus© Citations 19 34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimization of solvent-free enzymatic esterification in eutectic substrate reaction mixtureThe Candida rugosa lipase catalyzed esterification of (-)-menthol and lauric acid (LA) was studied in a eutectic mixture formed by both substrates((-)-menthol:LA 3:1, mol/mol). No additional reaction solvent was necessary, since the (-)-menthol:LA deep eutectic solvent (DES) acts as combined reaction medium and substrate pool. Therefore, the esterification is conducted under solvent-free conditions. The thermodynamic water activity (aw) was identified as a key parameter affecting the esterification performance in the (-)-menthol:LA DES. A response surface methodology was applied to optimize the esterification conditions in terms aw, amount of C. rugosa lipase (mCRL) and reaction temperature. Under the optimized reaction conditions (aw = 0.55; mCRL =60 mg; T =45 °C), a conversion of 95 ± 1% LA was achieved (one day), the final (-)-menthyl lauric acid ester concentration reached 1.36 ± 0.04 M (2.25 days). The experimental product formation rate agreed very well with the model prediction.Publicationtype: Journal ArticleScopus© Citations 26 287 694 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Synthesis of (-)-menthol fatty acid esters in and from (-)-menthol and fatty acids – novel concept for lipase catalyzed esterification based on eutectic solvents(2018-10); ; ; ; Deep eutectic solvents (DESs) based on (-)-menthol and fatty acids (octanoic, decanoic and dodecanoic acid) were investigated as reaction media for the lipase catalyzed esterification of the DES compounds itself to synthesize (-)-menthol fatty acid esters. The DES acts as reaction medium and substrate pool simultaneously without the need of adding any solvent. Candida rugosa lipase was active in the neat (-)-menthol:fatty acid DESs to synthesize (-)-menthol fatty acid esters. This example shows for the first time that a valuable product can be enzymatically produced using both components of a DES without any co-solvent. The addition of water to the DESs enhanced the reaction outcome likely due to interfacial activation of the enzyme. In biphasic reaction systems with an addition of 10 wt% of water to the DES phase, the conversion (7 d) of octanoic, decanoic and dodecanoic acid reached 50%, 83% and 71%, respectively. This corresponds to a batch productivity of 133 g L −1 d −1 (24 h) and a final (-)-menthyl dodecanoate concentration of 957 mM (7 d) in the (-)-menthol:dodecanoic acid DES. Closer investigation of this DES reaction system revealed that water addition and stirring speed are interacting parameters to optimize the process. The developed DES reaction systems represent neat reactant mixtures enabling the lipase catalyzed esterification under solvent-free conditions.Publicationtype: Journal Article218 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Deep Eutectic Solvents als neuartige Reaktionsmedien in der Biokatalyse(2016-01); ; ; Publicationtype: Journal Article180