FERULATE CROSS-LINKS LIMIT THE ENZYMATIC DEGRADATION OF SYNTHETICALLYLIGNIFIED PRIMARY WALLS OF MAIZE

Ferulate cross-linking of arabinoxylans to lignin may restrict the enz ymatic degradation of structural polysaccharides, limiting the utiliza tion of graminaceous crops and crop residues as feedstuffs and as feed stocks for fuel and chemical production. Maize walls from nonlignified cell suspensions with ca. 5.1 or 17.6 mg g(-1) of ferulates were synt hetically lignified with coniferyl alcohol and H2O2 to form dehydrogen ation polymer-cell wall complexes with ca. 4.8 or 15.8 mg g(-1) of fer ulates incorporated into lignin. Ferulate concentrations in cell walls were reduced from normal levels by growing cell suspensions with 2-am inoindan-2-phosphonic acid or by methylating wall ferulates with diazo methane prior to complex formation. A 70% reduction in ferulate-lignin cross-linking increased carbohydrate solubilization by 24-46% after 6 h and by 0-25% after 72 h of hydrolysis with two fungal enzyme mixtur es. Reduced cross-linking enhanced the hydrolysis of xylans and, to a lesser degree, cellulose from walls. The results presented indicate th at reduced feruloylation of arabinoxylans will significantly improve t he hydrolysis of lignified grass walls.