Bioresource Technology, Volume 163, July 2014, Pages 320-327.
Chenhuan Laia, b, Maobing Tub, , , Zhiqiang Shib, Ke Zhenga, Luis G. Olmosc, Shiyuan Yua
a-College of Chemical Engineering, Nanjing Forestry University, 159 Longpan Road, Nanjing, Jiangsu 210037, China and
b-Forest Products Laboratory and Center for Bioenergy and Bioproducts, Auburn University, 520 Devall Drive, Auburn, AL 36849, United States and
c-Department of Chemical and Natural Gas Engineering, Texas A&M University, 700 University Blvd, Kingsville, TX 78363, United States.
The interactions between lignin and cellulase enzymes play essential roles in the effective hydrolysis of lignocellulosic biomass. Delignification has long been associated with pretreatment efficiency and substrate digestibility. However, recently we found that lignin is a double-edged sword. On the contrary to its negative role in limiting lignocellulosic hydrolysis, lignin can enhance the enzymatic hydrolysis significantly depending on its physicochemical structure. In this study, organosolv pretreated sweetgum (OPSG) were used to quantitatively elucidate the positive role of lignin on enzymatic hydrolysis. We observed that the addition of organosolv lignin (EOL-SG) from sweetgum increased the 72-h hydrolysis yield of significantly improved the 72 h hydrolysis yields of organosolv pretreated sweetgum (OPSG) and loblolly pine (OPLP) from 49.3% to 68.6% and from 41.2% to 60.8%, respectively. In contrast, the addition of EOL-LP from loblolly pine decreased the 72 h hydrolysis yields of OPSG and OPLP to 42.0% and 38.1%, respectively. A strong correlation between the distribution coefficients of cellulase enzymes on lignins and the changes of hydrolysis yields indicated that the inhibitory or stimulatory effects of organosolv lignins on enzymatic hydrolysis were governed by the distribution coefficients (R). The different R values probably were related to the electrostatic interactions, hydrophobic interactions and hydrogen bondings between enzymes and lignin. The results of our work suggested organosolv lignin and residual lignin play distinct roles in enzymatic hydrolysis and turning residual lignin to organosolv lignin in pretreatment has great potential to improve the effectiveness of enzymatic hydrolysis.