Abstract
Interests remain in searching for cofactor regeneration system with higher efficiency at lower substrate cost. Glucose dehydrogenase (GDH) system has been dominant in NADH regeneration, but it only has a theoretical yield of one NADH per glucose molecule. This work sought to explore the utility of a two-step ethanol utilization pathway (EUP) in pathway-based NADH regeneration. The pathway runs from ethanol to acetaldehyde and to acetyl-CoA with each step generating one NADH, that together results in a higher theoretical yield of two NADH per ethanol molecule. In this project, anaerobic biotransformation of ketone (acetophenone or butanone) to alcohol by cpsADH from Candida parapsilosis was used as readout for evaluating relative efficacy and operating modes for EUP cofactor regeneration in Escherichia coli BL21 (DE3). Experiment tests validated that EUP was more efficient than GDH in NADH regeneration. Further, growing cell delivered higher biotransformation efficiency compared to resting cell due to the driving force generated by cell growth. Finally, preculture or cultivation in M9 + 10 g/L ethanol medium delivered higher biotransformation efficiency compared to LB medium. Overall, EUP could help regenerate NADH in support of a biocatalytic reaction, and is more efficient in cofactor regeneration than GDH.
Highlights
Cofactor dependent oxidoreductases play a hugely important role in biocatalysis and biotransformation
A cofactor regeneration system utilizes an enzyme to convert a sacrificial substrate to a second product that in the process help regenerate the cofactor needed by the main biotransformation reaction
Work in the biocatalysis field has been on the search for low-cost sacrificial substrate/enzyme system that could be usefully tapped for cofactor regeneration without posing separation concerns for the main biotransformation product [7, 8]
Summary
Cofactor dependent oxidoreductases play a hugely important role in biocatalysis and biotransformation. The enzymatic cofactor regeneration system works in tandem with the main biotransformation reaction to help convert the main biotransformation substrate into the target product. The main benefit of a cofactor regeneration system is in shifting the cost burden from provision of expensive cofactor to that of the sacrificial substrate, which could be low-cost [6] Another less often noted concern in cofactor regeneration is the generation of a byproduct that could complicate the downstream separation of the main biotransformation product [6]. Work in the biocatalysis field has been on the search for low-cost sacrificial substrate/enzyme system that could be usefully tapped for cofactor regeneration without posing separation concerns for the main biotransformation product [7, 8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
