Lignin impact on fiber degradation. IV. Enzymatic saccharification and in 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 selective solvent delignification (SSD), as well as the nutritive value of the residual biomass (co-product), was determined. The SSD pretreatment reduced lignin concentrations in grasses but not in alfalfa. Associated effects were increases in concentrations of neutral detergent fiber (NDF) due to losses of cell solubles (all forages) and changes in hemicellulose/cellulose ratio. SSD pretreatment increased IVDDM of the grasses by 11–25%, and this increase was highly correlated with the extent of delignification (r = 0.90). Extent of enzymatic fiber hydrolysis was up to 78%, with reducing sugar production of up to 371 mg/g DM. Differences in forage digestibility caused by stage of maturity were largely overcome by the SSD pretreatment. Fiber composition and IVDDM concentration of the co-products were indicative of low to medium nutritive value. SSD pretreatment seems uniquely capable of enhancing enzymatic saccharification and digestibility of mature, high-yielding grasses, such as giant wildrye.