Abstract
One of the challenges in biocatalysis is the development of stable and efficient bi-enzymatic cascades for bio-redox reactions coupled to the recycling of soluble cofactors. Aldo-keto reductase (LEK) and glucose dehydrogenase (GDH) can be utilized as the NADPH recycling system for economic and efficient biocatalysis of (R)-4-chloro-3-hydroxybutanoate ((R)-CHBE), an important chiral pharmaceutical intermediate. The LEK and GDH was efficiently co-immobilized in mesocellular siliceous foams (MCFs) under microwave irradiation (CoLG-MIA). while they were also co-immobilized by entrapment in calcium alginate without MIA as control (CoLG-CA). The relative activity of CoLG-MIA was increased to 140% compared with that of free LEK. The CoLG-MIA exhibited a wider range of pH and temperature stabilities compared with other preparations. The thermal, storage and batch operational stabilities of microwave-assisted immobilized LEK-GDH were also improved. The NADPH recycling system exhibited the potential as the stable and efficient catalyst for the industrial preparation of (R)-CHBE.
Highlights
The continuous regeneration of expensive cofactors in their active forms increases the cost efficiency of the biocatalysis process
MicrowaveTM Synthesis System was purchased from Discover (MARS5, CEM, USA)
The Histagged protein was mainly released by the elution buffer of 200–400 mM imidazole, and the apparent purity was over 90% by gray scanning (Fig 1)
Summary
The continuous regeneration of expensive cofactors in their active forms increases the cost efficiency of the biocatalysis process. Particular attention has been devoted to the in situ regeneration of redox cofactors such as NADPH or NADH, by varieties of techniques (e.g., chemical, photochemical, and enzymatic) [1, 2]. Enzyme-mediated redox-cofactor recycling system is preferred because of the high selectivity and efficiency in the industrial manufacture [3, 4]. The desired redox reaction by the main enzyme as well as the cofactor and cofactor-recycling reaction by the recycling dehydrogenase are coupled and performed simultaneously [5]. The immobilization of the enzymes that were involved in the redox cascade allows facile separation of immobilized enzyme and substrate product, no residual.
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