Alkaline sulfite/anthraquinone pretreatment followed by disk refining ofPinus radiataandPinus caribaeawood chips for biochemical ethanol production

Abstract

AbstractBACKGROUND:Alkaline sulfite/anthraquinone (ASA) cooking ofPinus radiataandPinus caribaeawood chips followed by disk refining was used as a pretreatment for the production of low lignified and high fibrillated pulps. The pulps produced with different delignification degrees and refined at different energy inputs (250, 750 and 1600 Wh) were saccharified with cellulases and fermented to ethanol withSaccharomyces cerevisiaeusing separated hydrolysis and fermentation (SHF) or semi‐simultaneous saccharification and fermentation (SSSF) processes.RESULTS:Delignification of ASA pulps was between 25% and 50%, with low glucans losses. Pulp yield was from 70 to 78% for pulps ofP. radiataand 60% for the pulp ofP. caribaea. Pulps obtained after refining were evaluated in assays of enzymatic hydrolysis. Glucans‐to‐glucose conversion varied from 20 to 70%, depending on the degree of delignification and fibrillation of the pulps. The best ASA pulp ofP. radiatawas used in SHF and SSSF experiments of ethanol production. Such experiments produced maximum ethanol concentration of 20 g L−1, which represented roughly 90% of glucose conversion and an estimated amount of 260 L ethanol ton−1wood.P. caribaeapulp also presented good performance in the enzymatic hydrolysis and fermentation but, due to the low amount of cellulose present, only 140 L ethanol would be obtained from each ton of wood.CONCLUSION:ASA cooking followed by disk refining was shown to be an efficient pretreatment process, which generated a low lignified and high‐fibrillated substrate that allowed the production of ethanol from the softwoods with high conversion yields. Copyright © 2012 Society of Chemical Industry