Chemoenzymatic lignin valorization: Production of epoxidized pre-polymers using Candida antarctica lipase B

An innovative chemoenzymatic catalytic system for functionalizing lignin from Organosolv and Kraft pulping processes to obtain oxirane rings was investigated. Novozym435 (immobilized C. antarctica lipase B: CalB) was used to catalyze the peroxidation of caprylic acid to peroxycaprylic acid, which in turn reacted with unsaturated CC bonds to form the oxirane ring. The conversion of OH groups to oxirane rings (epoxides) reached 90% and 55% after 12 h for the two processes, respectively. The residual enzyme activity over the time course of the reactions indicated transient denaturing due to association with the lignin substrate (10-50%) as well as irreversible denaturation due to exposure to hydrogen peroxide. Functionalized lignin has potential applications in the production of epoxy adhesive resins, and chemoenzymatic synthesis represents a “greener” pathway to this synthesis.