Lignocellulosic biomass offers a vast, renewable resource for
the sustainable production of fuels, chemicals, and materials.
To date, polysaccharides have been the primary biomass fraction
of interest in selective conversion processes, leaving
signicant opportunities for valorizing underutilized components
such as lignin.1–3 Lignin, a heterogeneous aromatic
polymer, is the second most abundant biopolymer aer
cellulose, representing 15 to 40% dry weight of plants; despite
its abundance, the inherent heterogeneity and recalcitrance of
lignin typically limits its use to heat and power in biochemical
conversion processes.2,4 However, as next generation biore
neries come online to produce carbohydrate-derived fuels at
commodity scale, large quantities of lignin will be generated,
with recent analysis indicating that lignin valorization can play
a key role for their economic viability and environmental
sustainability.1,3,5
In nature, lignin depolymerization is accomplished
primarily by powerful oxidative enzymes secreted by rot fungi
and some bacteria.6 This process releases aromatic monomers
during plant cell wall deconstruction, and multiple strategies
have evolved for metabolism of these aromatic species. The
most studied aromatic catabolic approach employs upper
pathways to channel aromatic molecules into the b-ketoadipate