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: Call) was used to catalyze the peroxidation of caprylic acid to peroxycaprylic acid, which in turn reacted with unsaturated C-C 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.