Torge Vorhaben

Development of effective nanobiocatalytic systems through the immobilization of hydrolases on functionalized carbon-based nanomaterials

In this study we report the use of functionalized carbon-based nanomaterials, such as amine-functionalized graphene oxide (GO) and multi-walled carbon nanotubes (CNTs), as effective immobilization supports for various lipases and esterases of industrial interest. Structural and biochemical characterization have revealed that the curvature of the nanomaterial affect the immobilization yield, the catalytic behavior and the secondary structure of enzymes. Infrared spectroscopy study indicates that the catalytic behavior of the immobilized enzymes is correlated with their α-helical content. Hydrolases exhibit higher esterification activity (up to 20-fold) when immobilized on CNTs compared to GO. The covalently immobilized enzymes exhibited comparable or even higher activity compared to the physically adsorbed ones, while they presented higher operational stability. The enhanced catalytic behavior observed for most of the hydrolases covalently immobilized on amine-functionalized CNTs indicate that these functionalized nanomaterials are suitable for the development of efficient nanobiocatalytic systems.

Immobilization of two (R)-Amine Transaminases on an Optimized Chitosan Support for the Enzymatic Synthesis of Optically Pure Amines

Two (R)‐selective amine transaminases from Gibberella zeae (GibZea) and from Neosartorya fischeri (NeoFis) were immobilized on chitosan as a carrier to improve their application in the biocatalytic synthesis of chiral (R)‐amines. An (S)‐selective enzyme from Vibrio fluvialis (VfTA) was used for comparison. After improving the immobilization conditions, all enzymes could be efficiently immobilized. Additionally, the thermal stability of GibZea and NeoFis could be improved and also a slight shift of the pH optimum was observed for GibZea. All enzymes showed good activity in the conversion of α‐methylbenzylamine. In the asymmetric synthesis of (R)‐2‐aminohexane from the corresponding ketone, a 13.4‐fold higher conversion (>99 %) was found for the immobilized GibZea compared to the free enzyme. Hence, the covalent binding with glutaraldehyde of these enzymes on chitosan beads resulted in a significant stabilization of the amine transaminases investigated.

Plasma-Modified Polypropylene as Carrier for the Immobilization of Candida antarctica Lipase B and Pyrobaculum calidifontis Esterase

In this work, the immobilization of two hydrolases on plasma‐modified polypropylene carriers was investigated. Treating Accurel MP1001 with an oxygen plasma was found most suitable to increase the hydrophilicity and to allow for efficient immobilization. Thus, for lipase B from Candida antarctica and for an esterase from Pyrobaculum calidifontis esterase (PestE) a 5‐fold and 14‐fold increase, respectively, in immobilization yield resulted compared to untreated carrier. In contrast to the oxygen‐modified support, modification of the polypropylene carrier with ammonia plasma showed no positive effect. Furthermore, it could be shown that immobilized PestE catalyzed enantioselective transesterification of α‐phenylethanol in vinyl acetate, whereas the free enzyme showed no activity. Both hydrolases could be recycled five times without significant loss of activity.