Using low temperature to balance enzymatic saccharification and furan formation during SPORL pretreatment of Douglas-fir

• Published in: Process biochemistry (1991) 2014-03, Vol.49 (3), p.466-473
• Main Authors: Zhang, C., Houtman, C.J., Zhu, J.Y.
• Format: Article
• Language: English
• Subjects: activation energy; biotransformation; Combined severity/hydrolysis factor; Degradation; delignification; enzymatic hydrolysis; Enzymatic hydrolysis/saccharification; Furans; hemicellulose; Hydrolysis; Kinetics; lignin; Lignocellulose; Low temperature pretreatment; Moles; Pretreatment; Pseudotsuga menziesii; Saccharification; Sugar degradation/inhibitor formation; Sugars; sulfites; synthesis; temperature; Woody biomass
• ISSN: 1359-5113; 1873-3298
• DOI: 10.1016/j.procbio.2013.12.017

•Combined hydrolysis factor (CHF) to predict hemicellulose dissolution and furan formation.•Pretreatment severity CHF to design low temperature pretreatment.•Balancing enzymatic saccharification and furan formation at low pretreatment temperature.•Excellent sugar yield with very low furan production from Douglas-fir by SPORL at 165°C. Comparing analytical results for Sulfite Pretreatment to Overcome the Recalcitrance of Lignocelluloses (SPORL) of Douglas-fir (Pseudotsuga menziesii) at two different temperatures shows that the apparent activation energy of sugar degradation is higher than that of hemicellulose hydrolysis, approximately 161kJ/mole versus 100kJ/mole. Thus, one can balance the production of degradation products against hemicellulose hydrolysis and therefore the enzymatic saccharification efficiency of the resultant substrate by changing pretreatment temperature and duration. Specifically, pretreatment at 165°C for 75min significantly reduced furan formation compared with the pretreatment at 180°C for 30min while maintaining the same pretreatment severity and therefore the same substrate enzymatic digestibility (SED). Obtaining high SED with Douglas-fir is also limited by lignin content. Fortunately, the bisulfite in SPORL provides delignification activity. By combining kinetic models for hemicelluloses hydrolysis, sugar degradation, and delignification, the performance of pretreatment can be optimized with respect to temperature, duration, acid, and bisulfite loading. The kinetic approach taken in this study is effective to design viable low temperature pretreatment processes for effective bioconversion of lignocelluloses.