Adsorption of high-purity endo-1,4-β-glucanases from Trichoderma reesei on components of lignocellulosic materials: Cellulose, lignin, and xylan

From one strain of Trichoderma reesei, six different types of endoglucanase, which had been purified to homogeneity, varied in the intensity of their binding to cellulose (for comparison) and varied in similar order in their binding to lignins from birch and larch and to spruce lignocarbohydrate complex. Estimated strengths of binding (in terms of partition coefficients, K p, between sorbent and water phase) were uniformly low on xylan ( K p < 0.3 l g −1) but ranged up to K p = 2.8 l g −1 on cellulose and 1.9 on larch lignin, i.e., well above K p = 11 g −1, at which some 90% of the enzyme is sorbed. When sorbed on lignin, endoglucanases lost activity (which would have been retained in aqueous media, with or without pure cellulose). Addition of 0.125 to 0.375% of lignin to a (0.25%) cellulose digestion decreased conversion two- to three-fold over 24 h and stopped hydrolysis within 50 h. This inactivating effect of lignin was observed also with steam-exploded lignocellulose, but not if the latter was acid-treated, nor with lignocarbohydrate complex.