LIGNIN IMPACT ON FIBER DEGRADATION .4. ENZYMATIC SACCHARIFICATION ANDIN-VITRO DIGESTIBILITY OF ALFALFA AND GRASSES FOLLOWING SELECTIVE SOLVENT DELIGNIFICATION

The response in composition, in vitro dry matter digestibility (IVDDM) , and enzymatic saccharification, of alfalfa and various grasses to se lective solvent delignification (SSD), as well as the nutritive value of the residual biomass (co-product), was determined. The SSD pretreat ment reduced lignin concentrations in grasses bur not in alfalfa. Asso ciated effects were increases in concentrations of neutral detergent f iber (NDF) due to losses of cell solubles (all forages) and changes in hemicellulose/cellulose ratio. SSD pretreatment increased IVDDM of th e grasses by 11-25%, and this increase was highly correlated with the extent of delignification (r = 0.90). Extent of enzymatic fiber hydrol ysis was up to 78%, with reducing sugar production of up to 371 mg/g D M. Differences in forage digestibility caused by stage of maturity wer e largely overcome by the SSD pretreatment. Fiber composition and IVDD M concentration of the co-products were indicative of low to medium nu tritive value. SSD pretreatment seems uniquely capable of enhancing en zymatic saccharification and digestibility of mature, high-yielding gr asses, such as giant wildrye. (C) 1997 Published by Elsevier Science L td.