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Title: Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight

Abstract

Lignocellulose is a promising feedstock for biofuel production, while lignin poses a grand challenge on the entire process, especially enzymatic hydrolysis. In this study, different types of lignin inhibited enzymatic hydrolysis by different mechanisms. Organosolv lignin from Loblolly pine adsorbed enzyme nonproductively and reduced the available enzyme for cellulose, therefore decreasing hydrolysis rate and ultimate sugar yield. Kraft pine lignin precipitated on the surface of cellulose, preventing it from contacting with enzyme. The molecular weight influenced the inhibition effect of lignin. Lignin of lower molecular weight could bind enzyme nonproductively and when the molecular weight increased, the steric repulsion caused by lignin deposition on cellulose became more significant. The NMR analysis revealed that lignin structural features, e.g., functional groups, S/G ratio, determined the behaviors of lignin in enzymatic hydrolysis. High content of aliphatic hydroxyl groups, or low content of carboxylic groups led to high surface hydrophobicity, increasing the adsorption between lignin and enzyme. In addition, the substrate reactivity is also an important factor that affects enzymatic hydrolysis. Cellulose with higher crystallinity exhibited slower hydrolysis rate and lower conversion. When the crystallinity index increased from 0.43 to 0.72 and 0.81, the ultimate conversion decreased from 80 to 68% and 57%, respectively.

Authors:
 [1];  [2];  [2];  [3];  [1];  [1];  [1]
  1. Clemson Univ., SC (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1474540
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Renewable Energy
Additional Journal Information:
Journal Volume: 123; Journal Issue: C; Journal ID: ISSN 0960-1481
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Li, Xiang, Li, Mi, Pu, Yunqiao, Ragauskas, Arthur J., Klett, Adam S., Thies, Mark, and Zheng, Yi. Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight. United States: N. p., 2018. Web. doi:10.1016/j.renene.2018.02.079.
Li, Xiang, Li, Mi, Pu, Yunqiao, Ragauskas, Arthur J., Klett, Adam S., Thies, Mark, & Zheng, Yi. Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight. United States. doi:10.1016/j.renene.2018.02.079.
Li, Xiang, Li, Mi, Pu, Yunqiao, Ragauskas, Arthur J., Klett, Adam S., Thies, Mark, and Zheng, Yi. Tue . "Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight". United States. doi:10.1016/j.renene.2018.02.079. https://www.osti.gov/servlets/purl/1474540.
@article{osti_1474540,
title = {Inhibitory effects of lignin on enzymatic hydrolysis: The role of lignin chemistry and molecular weight},
author = {Li, Xiang and Li, Mi and Pu, Yunqiao and Ragauskas, Arthur J. and Klett, Adam S. and Thies, Mark and Zheng, Yi},
abstractNote = {Lignocellulose is a promising feedstock for biofuel production, while lignin poses a grand challenge on the entire process, especially enzymatic hydrolysis. In this study, different types of lignin inhibited enzymatic hydrolysis by different mechanisms. Organosolv lignin from Loblolly pine adsorbed enzyme nonproductively and reduced the available enzyme for cellulose, therefore decreasing hydrolysis rate and ultimate sugar yield. Kraft pine lignin precipitated on the surface of cellulose, preventing it from contacting with enzyme. The molecular weight influenced the inhibition effect of lignin. Lignin of lower molecular weight could bind enzyme nonproductively and when the molecular weight increased, the steric repulsion caused by lignin deposition on cellulose became more significant. The NMR analysis revealed that lignin structural features, e.g., functional groups, S/G ratio, determined the behaviors of lignin in enzymatic hydrolysis. High content of aliphatic hydroxyl groups, or low content of carboxylic groups led to high surface hydrophobicity, increasing the adsorption between lignin and enzyme. In addition, the substrate reactivity is also an important factor that affects enzymatic hydrolysis. Cellulose with higher crystallinity exhibited slower hydrolysis rate and lower conversion. When the crystallinity index increased from 0.43 to 0.72 and 0.81, the ultimate conversion decreased from 80 to 68% and 57%, respectively.},
doi = {10.1016/j.renene.2018.02.079},
journal = {Renewable Energy},
number = C,
volume = 123,
place = {United States},
year = {2018},
month = {2}
}

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