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Title: New perspective on glycoside hydrolase binding to lignin from pretreated corn stover

Background: Non-specific binding of cellulases to lignin has been implicated as a major factor in the loss of cellulase activity during biomass conversion to sugars. It is believed that this binding may strongly impact process economics through loss of enzyme activities during hydrolysis and enzyme recycling scenarios. The current model suggests glycoside hydrolase activities are lost though non-specific/non-productive binding of carbohydrate-binding domains to lignin, limiting catalytic site access to the carbohydrate components of the cell wall. Results: In this study, we compared component enzyme affinities of a commercial Trichoderma reesei cellulase formulation, Cellic CTec2, towards extracted corn stover lignin using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and p-nitrophenyl substrate activities to monitor component binding, activity loss, and total protein binding. Protein binding was strongly affected by pH and ionic strength. β-D-glucosidases and xylanases, which do not have carbohydrate-binding modules (CBMs) and are basic proteins, demonstrated the strongest binding at low ionic strength, suggesting that CBMs are not the dominant factor in enzyme adsorption to lignin. Despite strong adsorption to insoluble lignin, β-D-glucosidase and xylanase activities remained high, with process yields decreasing only 4–15 % depending on lignin concentration. Conclusion: We propose that specific enzyme adsorption to lignin from a mixture ofmore » biomass-hydrolyzing enzymes is a competitive affinity where β-D-glucosidases and xylanases can displace CBM interactions with lignin. Process parameters, such as temperature, pH, and salt concentration influence the individual enzymes’ affinity for lignin, and both hydrophobic and electrostatic interactions are responsible for this binding phenomenon. Moreover, our results suggest that concern regarding loss of critical cell wall degrading enzymes to lignin adsorption may be unwarranted when complex enzyme mixtures are used to digest biomass.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. NIST, Boulder, CO (United States)
  3. Dept. of Veterans Affairs, Boise, ID (United States)
Publication Date:
Report Number(s):
NREL/JA-2700-64797
Journal ID: ISSN 1754-6834
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Related Information: Biotechnology for Biofuels; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); Alliance for Sustainable Energy, LLC (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; lignin; glycosyl hydrolase; enzyme binding; cellulase; biomass; pretreatment; Glycoside hydrolase
OSTI Identifier:
1236147
Alternate Identifier(s):
OSTI ID: 1239800