Rational design of flavoprotein oxidases for biocatalytic valorization of lignin-derived monomers

Biocatalytic valorization of lignin-derived phenolic compounds has emerged as a promising biorefinery strategy in the challenging production of value-added fine chemicals. VAO(vanillyl alcohol oxidase)-type oxidases are promising biocatalysts for modifying lignin-derived phenols. Mechanistic studies on the prototype VAO have revealed that a pivotal product intermediate, a quinone methide, is transiently formed and allows several different oxidation reactions. The work described in this thesis aimed to develop robust VAO-type enzymes that selectively oxidize different lignin-derived phenols into valuable chemicals. For this, eugenol oxidase has been comprehensively investigated for tuning the stability, chemoselectivity and activity through sequence-, structure- and computation-aided enzyme engineering. Whole-cell or enzyme cascade reactions were developed to generate high value compounds starting from lignin-derived alkylphenols. Besides, a novel approach for performing biocatalytic oxidative amination via an “enzyme-trapped quinone methide” was developed. This expands the catalytic repertoire of VAO-type oxidases and offers new opportunities for upgrading lignin.