Development of an Efficient Bifunctional Endoxylanase/Feruloyl Esterase Chimera for Coproduction of Ferulic Acid, <i>p</i> -Coumaric Acid, and Xylooligosaccharides

Bifunctional endoxylanases/feruloyl esterases that can efficiently produce hydroxycinnamic acids and xylooligosaccharides from agricultural residues are highly desirable but underexplored. Here, we report the development of a bifunctional chimera, XynB-SnT-FaeB, which shares low sequence identity (<23%) with its homologues and contains a novel linker peptide. It can hydrolyze model hydroxycinnamate esters and xylans. Due to interdomain synergism, its feruloyl esterase and endoxylanase catalytic efficiencies (<i>k</i>_<i>cat</i><i>/K</i>_<i>m</i>) toward feruloylated arabinoxylan were 2.95 and 1.60 times those of FaeB and XynB, respectively. High yields of ferulic acid (6.06/2.99/3.01 mg/g), <i>p-</i>coumaric acid (1.82/14.48/19.37 mg/g), and xylooligosaccharides (154.35/26.68/112.10 mg/g) were produced simultaneously by using 15 μg of XynB-SnT-FaeB from 10 mg of corn bran/corn cob/corn stover, respectively. To the best of our knowledge, XynB-SnT-FaeB is the first enzyme designed specifically for the efficient production of hydroxycinnamic acids and xylooligosaccharides. This study demonstrates the great potential of chimeric endoxylanases/feruloyl esterases in the high-value utilization of corn residues.