Rewired phenolic metabolism and improved saccharification efficiency of a <i>Zea mays cinnamyl alcohol dehydrogenase 2 (zmcad2)</i> mutant

Lignocellulosic biomass is an abundant byproduct from cereal crops that can potentially be valorized as a feedstock to produce biomaterials. Zea mays CINNAMYL ALCOHOL DEHYDROGENASE 2 (ZmCAD2) involved in lignification, and promising target improve the cellulose-to-glucose conversion of maize stover. Here, we analyzed field-grown zmcad2 Mutator transposon insertional mutant. Zmcad2 mutant plants had 18% lower Klason lignin content, whereas their cellulose content was similar control lines. The mutants contained increased levels hydroxycinnamaldehydes, i.e. substrates ZmCAD2, ferulic acid tricin. Ferulates decorating hemicelluloses were not altered. Phenolic profiling further revealed hydroxycinnamaldehydes are partly converted into (dihydro)ferulic sinapic derivatives mutants. Syringyl lactic hexoside, metabolic sink CAD-deficient dicot trees, appeared maize. enzymatic efficiency determined after 10 different thermochemical pre-treatments. yielded significantly higher conversions compared with controls for almost every pre-treatment. However, relative increase glucose yields alkaline pre-treatment than when no applied, suggesting positive effect incorporation leveled off by negative reduced p-coumarate cell wall. Taken together, our results reveal how phenolic metabolism affected maize, support mutating CAD genes strategy lignocellulosic sugar-platform biorefineries.