Organosolv delignification of white- and brown-rotted Eucalyptus grandis hardwood

Sound (undecayed control) and fungally-pretreated wood samples were submitt ed to organosolv delignification. The cooking liquor used was methanol/wate r (78:22 v/v) containing CaCl2 and MgSO4 each at a concentration of 25 mmol dm(-3), The cooking process was performed at 180 degrees C for reaction ti mes varying from 5 to 100 min. Despite some differences in. the lignin remo val pattern, pseudo-first order kinetic models permitted a prediction of de lignification rate constants for all experiments, All biodegraded samples p rovided higher delignification rate constants than the undecayed control (2 .0 x 10(-2)min(-1) for the undecayed control and, for example, 14.2 x 10(-2 )min(-1) for the sample decayed by Trametes versicolor for 2.5 months), Bio degraded samples also presented significantly increased xylan removal rates . The type of biodegradation affected the behavior of wood samples under or ganosolv pulping, The highest delignification and xylan removal rate consta nts were observed in the sample decayed by T versicolor for 2.5 months (17% weight loss). However, high delignification and xylan removal rate constan ts were also observed in the sample decayed by Punctularia artropurpascens for only 0.5 months (1.2% weight loss). Data obtained from a single fungal species pretreatment or data from all fungal pretreatments indicated that t here is no clear correlation between the delignification constants and the wood weight or component losses. This lack of correlation suggested that th e structure of residual polymers in decayed wood affects the delignificatio n process in the organosolv pulping more than the removal extent of each in dividual component. (C) 2000 Society of Chemical Industry.