LAUSR

Significance Upgrading lignin, an underutilized component of biomass, is essential for sustainable biorefining. Biocatalysis has considerable potential for upgrading lignin, but our lack of knowledge of relevant enzymes and pathways has limited its application. Herein, we describe a microbial pathway that catabolizes acetovanillone, a major component of several industrial lignin streams. This pathway is unusual in that it involves phosphorylation and carboxylation before conversion to the intermediate, vanillate, which is degraded via the β-ketoadipate pathway. Importantly, the hydroxyphenylethanone catabolic pathway enables bacterial growth on softwood lignin pretreated by oxidative catalytic fractionation. Overall, these insights greatly facilitate the engineering of bacteria to biocatalytically upgrade lignin.