Alginate Encapsulation Stabilizes Xylanase Toward the Laccase Mediator System

Xylanase, a hydrolytic enzyme, is susceptible to inactivation by the oxidative conditions generated by the laccase mediator system (LMS). Given the impetus to develop a mixed enzyme system for application in biomass processing industries, xylanase was encapsulated with either Cu- or Ca-alginate and then exposed to the LMS with variations such as mediator type, mediator concentration, and treatment pH. Results demonstrate that alginate-encapsulated xylanase retains substantial activity (> 80%) when exposed to the LMS relative to non-encapsulated xylanase. Cu-alginate generally provided better protection than Ca-alginate for all mediators, and protection was observed even at a low pH, where the LMS is most potent. Despite encapsulation, xylanase was still capable of hydrolyzing its polymeric substrate xylan, given k/K values within an order of magnitude of that for non-encapsulated xylanase. The alginate matrix does not impede the function of the oxidized mediator, since comparable V values were observed for the conversion of veratryl alcohol to veratraldehyde by free and Cu-alginate encapsulated laccase. Overall, these results support development of a mixed enzyme system for biomass delignification and, more broadly, show potential for protecting protein function in an oxidative environment.