Charakterisierung und Optimierung gel-stabilisierter Zwei-Phasen-Systeme zur stereospezifischen Reduktion hydrophober Verbindungen mit der Carbonyl-Reduktase aus Candida parapsilosis
Enzymes are increasingly being used for the production of chiral compounds with high enantiomeric purity for the synthesis of fine chemicals and pharmaceuticals. Reason for this lies mainly in the high substrate and reaction specificity of many biocatalysts. Interesting starting compounds are often not or only slightly soluble in water. The employment of an organic solvent offers a convenient alternative to the aqueous system. Use of a gel-stabilized two-phase-system could avoid an inactivation of the sensitive biocatalysts by the solvent. The biocatalysts are protected in the hydrogel from the detrimental effects of the solvent which serves as a reservoir for the poor water soluble substrate. The conversion of hydrophobic substrates with immobilized biocatalysts could be shown by the example of the stereospecific reduction of p-bromo-acetophenone with the carbonyl reductase from candida parapsilosis (CPCR).The purified CPCR could be used in pure aqueous systems, aqueous-organic two-phase-systems and gel-stabilized two-phase-systems. The cofactor NADH + H+ is essential for the reduction of keto groups. To avoid stoichiometric amounts, regeneration of the cofactor is necessary and was investigated by a substrate-coupled mode with 2-propanol and an enzyme-coupled mode with the formate dehydrogenase from candida boidinii (FDH). Both reactions were optimized. The biocatalysts could be immobilized successfully in polyvinyl alcohol beads and into a thermosensitive matrix, based on polyacrylamide. Optimization of the reaction conditions for the biocatalysis took place in one- and two-phase-systems. The activity and stability of the in PVA-immobilized biocatalysts were compared with the ones in aqueous systems and aqueous-organic two-phase-systems.
info:eu-repo/classification/ddc/570, Biowissenschaften, Biologie, Biokatalyse, Immobilisierung, gel-stabilisiertes Zwei-Phasen-System, Carbonyl-Reduktase, Formiat-Dehydrogenase, biocatalysis, immobilization, gel-stabilized two-phase-system, carbonyl reductase, formate dehydrogenase
Networked Digital Library of Theses and Dissertations
Publikationsserver der RWTH Aachen University