Hydrophilized Silicone Matrix for the Preparation of Stable Carbonyl Reductase Immobilizates

Abstract

Industrial use of enzymes requires high activity, stability, and manageability under technical conditions. Therefore, most biocatalysts are immobilized before use, often by physical adsorption onto a solid carrier. However, a major limitation for the technical use of such immobilizates is the insufficient operational stability under process conditions resulting from enzyme leaching and carrier disintegration. Our group demonstrated recently that for lipase‐catalyzed esterifications these limitations can be largely overcome by the formation of silCoat biocatalysts, composite materials of carrier‐bound enzymes and silicone. Here, we report the successful transformation of this method to the immobilization of carbonyl reductase (CR), an enzyme representing oxidoreductases as a completely different class of biocatalysts. The silCoat biocatalysts cannot be transferred directly to CR because they require an overall hydrophilic surrounding, which opposes the hydrophobicity of silicone. Consequently, the hydrophilization of the material is necessary to achieve reasonable enzyme activity. This was realized by the rational modification of the precursors for silicone formation and applied to increase the leaching stability and mechanical strength of the carrier‐bound CR. The resulting HYsilCoat CR had a significantly longer half‐life than that obtained through the uncoated preparation; the mechanical stability of an alumina carrier was increased by a factor of 120. This enables the consideration of mechanically unstable but environmentally friendly and/or cheap material as an enzyme carrier for industrial use.

Immobilised lipases in the cosmetics industry

“…217 By fine-tuning the used siloxane precursors, the mesh size of the polymer matrix can be tailored to allow the diffusion of small raw materials and products into and out of the immobilisates, while keeping the large enzyme in the particle. 217,218 Thereby enzyme desorption is prohibited without the need for covalent fixation (which usually results in significant loss of enzymatic activity). 200 Siloxane tuning also enables adjustment of the hydrophilicity degree providing applicability of the method to more or less hydrophobic reaction systems.…”

“…200 Siloxane tuning also enables adjustment of the hydrophilicity degree providing applicability of the method to more or less hydrophobic reaction systems. 218 Diffusion limitation is overall minimised by employment of solid particles for surfacial enzyme adsorption in the outer sphere of the particle (e.g. in Novozym 435) prior to entrapment, resulting in considerably higher residual activities 209,217 than with immobilisates based on only silicone.…”

Enzyme Immobilization by Microencapsulation: Methods, Materials, and Technological Applications

“…The matrix-material has thus been made suitable for encapsulation of hydrophilic enzymes such as carbonyl reductase (161).…”

Mit Silikon zum robusten Enzym

“…Die Kombination entsteht, indem poröse Trägermaterialien — etwa kommerzielle Polystyrol‐, Polyacryl‐ oder Polymethacrylatträger — mit einer Mischung aus divinylterminierten Polydivinylsiloxanen und Si‐H‐funktionalisierten Siloxanen imprägniert werden und dieses Gemisch dann Pt0‐katalysiert in situ vulkanisiert wird (Abbildung 1).6) Dabei bildet sich ein Kompositmaterial aus fester Träger‐ und elastischer Kunststoffphase 8. Je nach Mengenanteil des Silikons bleibt die Trägeraußenfläche frei zugänglich oder wird von einer geschlossenen Silikonschicht bedeckt 9,10…”

“…Silikone mit erhöhter Hydrophilie zur Kompositbildung zu nutzen, erhöht ebenfalls die Trägerstabilisierung und verringert die Enzymdesorption 10. Dabei wird an Stelle des divinylterminierten Poly(dimethyl)siloxans divinylterminiertes Poly(ethylen)glycol400 in die Hydrosilylierungsreaktion eingesetzt.…”