title: Identifying new lignin bioengineering targets: impact of epicatechin, quercetin glycoside, and gallate derivatives on the lignification and fermentation of maize cell walls.
abstract: Apoplastic targeting of secondary metabolites compatible with monolignol polymerization may provide new avenues for designing lignins that are less inhibitory toward fiber fermentation. To identify suitable monolignol substitutes, primary maize cell walls were artificially lignified with normal monolignols plus various epicatechin, quercetin glycoside, and gallate derivatives added as 0 or 45% by weight of the precursor mixture. The flavonoids and gallates had variable effects on peroxidase activity, but all dropped lignification pH. Epigallocatechin gallate, epicatechin gallate, epicatechin vanillate, epigallocatechin, galloylhyperin, and pentagalloylglucose formed wall-bound lignin at moderate to high concentrations, and their incorporation increased 48 h in vitro ruminal fiber fermentability by 20-33% relative to lignified controls. By contrast, ethyl gallate and corilagin severely depressed lignification and increased 48 h fermentability by about 50%. The results suggest several flavonoid and gallate derivatives are promising lignin bioengineering targets for improving the inherent fermentability of nonpretreated cell walls.
authors.affiliation: U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture , 1925 Linden Drive West, Madison, Wisconsin 53706, USA. john.grabber@ars.usda.gov
authors.forename: John H
authors.initials: JH
authors.lastname: Grabber
authors.forename: Dino
authors.initials: D
authors.lastname: Ress
authors.forename: John
authors.initials: J
authors.lastname: Ralph
mesh_terms: D000818:Animals; D001419:Bacteria / Q000378:metabolism; D057005:Bioengineering; D002392:Catechin / Q000031:analogs & derivatives / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D005285:Fermentation; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008031:Lignin / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism; D010636:Phenols / Q000378:metabolism; D010666:Phenylpropionates / Q000378:metabolism; D011794:Quercetin / Q000378:metabolism*; D012417:Rumen / Q000382:microbiology; D003313:Zea mays / Q000378:metabolism*
chemical_list: D010636:Phenols; D010666:Phenylpropionates; C048734:ethyl gallate; D005707:Gallic Acid; C496130:sinapyl alcohol; D002392:Catechin; D008031:Lignin; D011794:Quercetin; C010559:coniferyl alcohol; D009195:Peroxidase