Fibrillating wood chips to facilitate high-valued lignin extraction and high titer ethanol production

Abstract

In this study, a physical-chemical pretreatment strategy, using a twin-screw extrusion process for wood chips micro-fibrillation and subsequent chemical pretreatment with a recyclable acid hydrotrope, was developed to facilitate the extraction of high-valued lignin and the enzymatical hydrolysis of cellulose. At an optimum pretreatment severity of T70C70, the fibrillated wood chips were dissolved for approximately 89 % with a negligible loss of cellulose and considerable removals of lignin and hemicellulose (45 % and 65 %, respectively). The obtained lignin exhibited excellent structural profiles, such as high hydroxyl content (aliphatic OH of 2.31 mmol/g), more β-O-4 aryl ether linkages (59.05 %), low Mw (3736 g/mol), and narrow polydispersity (Mw/Mn, 2.03), according the characterization results from FTIR, TGA, GPC, 31P NMR, and 2D HSQC NMR measurements. The residual glucan-rich solid was enzymatically hydrolyzed for high titer ethanol production via a Q-SSF process, resulting in a high ethanol concentration of 47.62 g/L.