Fermentation Optimization of Cellobiose Dehydrogenase Catalyzed Production of Cellobionate for Fuels and Chemicals Production

Cellobiose dehydrogenase (CDH) is a flavoprotein containing two prosthetic groups, an FAD group and a heme group, residing in different domains.  In the presence of an electron acceptor (redox mediator), CDH will oxidize cellobiose to cellobionate, which can be used as a reactive intermediate for cellulosic ethanol production.  The redox mediator can be continuously regenerated by laccase, allowing the redox mediator to be present in only catalytic quantities.  Regeneration of the redox mediator and the extent of conversion to the product of interest are also dependent on dissolved oxygen level, pH, and the concentration of FAD.  Previous studies have shown that laccase can enzymatically regenerate a wide variety of redox mediators in the CDH catalyzed conversion of lactose to lactobionic acid.  In this study, we investigate the ability of laccase to regenerate a subset of those redox mediators, this time using cellobiose as the substrate.  Fermentation conditions were optimized based on pH, dissolved oxygen concentration, and FAD concentration for the redox mediators included in this study.