Bioethanol production from bio-organosolv pulps of Pinus radiata and Acacia dealbata

Wood chips from Pinus radiata and Acacia dealbata were pretreated with the white-rot fungi Cetiporiopsis subvermispora and Ganoderma australe, respectively, for 30 days at 27 degrees C and 55% relative humidity, followed by an organosolv delignification with 60% ethanol solution at 200 degrees C for 1 h to produce pulps with high cellulose and low lignin content. Biotreatment for 30 days was chosen based on low weight and cellulose losses (lower than 4%) and lignin degradation higher than 9%. After organosolv delignification, pulp yield for P. radiata and A. dealbata pulps was 45-49% and 31-51%, respectively. P. radiata bio-pulps showed higher glucan (93%) and lower lignin content (6%) than control pulps (82% glucan and 13% lignin). A. dealbata bio-pulps also showed higher glucan (95%) and lower lignin content (2%) than control pulps (92% glucan and 4% lignin). Pulp suspensions at 2% consistency were submitted either to separate enzymatic hydrolysis and fermentation (SHF) or simultaneous enzymatic saccharification and fermentation (SSF) for bioethanol production. The yeast Saccharomyces cerevisiae was used for fermentation. Glucan-to-glucose conversion in the enzymatic hydrolysis of control and bio-pulps of P. radiata was 55% and 100%, respectively, and it was 100% for all pulp samples case of A. dealbata. The highest ethanol yield (calculated as percentage of theoretical yield) during SHF of P. radiata control and bio-pulps was 38% and 55%, respectively, and for A. dealbata control and bio-pulps 62% and 69%, respectively. The SSF of P. radiata control and bio-pulps yielded 10% and 65% of ethanol, respectively, and 77% and 82% for A. dealbata control and bio-pulps, respectively. In wood basis, the maximum conversion obtained (g ethanol per kg wood) in SHF was 37% and 51% (for P. radiata and A. dealbata pulps, respectively) and 44% and 65% in SSF (for P. radiata and A. dealbata pulps, respectively) regarding the theoretical yield. The low wood-to-ethanol conversion was associated with low pulp yield (A. dealbata pulps), high residual lignin amount (P. radiata pulps) and the low pulp consistency (2%) used for SHF and SSF. (c) 2007 Society of Chemical Industry.