Award Abstract # 1605105
SusChEM: Integrated Studies on Interactions between Lignocellulosic Fine Structure and Hydrolytic Enzymes toward Efficient Hydrolysis

NSF Org: CBET
Division of Chemical, Bioengineering, Environmental, and Transport Systems
Recipient: MICHIGAN TECHNOLOGICAL UNIVERSITY
Initial Amendment Date: May 27, 2016
Latest Amendment Date: December 20, 2019
Award Number: 1605105
Award Instrument: Standard Grant
Program Manager: Carole Read
cread@nsf.gov
 (703)292-2418
CBET
 Division of Chemical, Bioengineering, Environmental, and Transport Systems
ENG
 Directorate for Engineering
Start Date: September 1, 2016
End Date: August 31, 2021 (Estimated)
Total Intended Award Amount: $310,716.00
Total Awarded Amount to Date: $310,716.00
Funds Obligated to Date: FY 2016 = $310,716.00
History of Investigator:
  • David Shonnard (Principal Investigator)
    drshonna@mtu.edu
  • Wen Zhou (Former Principal Investigator)
  • David Shonnard (Former Co-Principal Investigator)
Recipient Sponsored Research Office: Michigan Technological University
1400 TOWNSEND DR
HOUGHTON
MI  US  49931-1200
(906)487-1885
Sponsor Congressional District: 01
Primary Place of Performance: Michigan Technological University
1400 Townsend Drive
Houghton
MI  US  49931-1295
Primary Place of Performance
Congressional District:
01
Unique Entity Identifier (UEI): GKMSN3DA6P91
Parent UEI: GKMSN3DA6P91
NSF Program(s): EchemS-Electrochemical Systems
Primary Program Source: 01001617DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 8248
Program Element Code(s): 764400
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.041

ABSTRACT

Lignocellulosic plant biomass such as grass straw and agricultural residues has been recognized a low-cost, abundant, and renewable source of fermentable sugars for production of fuel alcohol and other value-added chemicals. Current processes deployed in cellulosic biofuel facilities use a mixture of enzymes to convert the cellulosic fractions to fermentable sugars. However, this process is still fairly slow and is the most expensive step in cellulosic biofuels production, in part because lignocellulosic biomass is recalcitrant to enzymatic attack and breakdown. This recalcitrance is due to the complexity of lignocellulose structure at the molecular and microscopic levels. Therefore, before enzyme treatment, the lignocellulosic biomass is pretreated, typically with a combination of steam and chemicals, to open up the pores in the biomass so that the enzyme can be more effective. There is a need to develop a better, molecular level understanding of the biomass breakdown processes to identify new strategies optimize or eliminate pretreatment and improve the rate of conversion to realize cost reduction. The goal of this project is to develop a fundamental understanding of how lignocellulosic biomass is broken down, or deconstructed, during enzyme treatment so that these new cost-saving strategies can be identified. The innovative aspect of this study is the combination of molecular modeling and molecular chemical imaging to discover more about this complex process. The educational activities associated with this project feature the development of a workbook on the conversion of biomass to biofuels for use in summer youth programs.

Lignocellulosic biomass is a three-dimensional biopolymer matrix of cellulose, hemicellulose, and lignin ordered at multiple scales ranging from the molecular scale to the microscale. The complexity of the lignocellulosic matrix has long been recognized as a key limiting factor in the efficiency of its enzymatic hydrolysis to fermentable sugars. This research will combine dynamic modeling and molecular imaging to gain new insights into the real-time dynamics of lignocellulosic molecular and fine structure changes during the conversion of lignocellulosic biomass to sugars using mixtures of hydrolytic enzymes. To accomplish this goal, the research has three objectives. The first objective is to gain a fundamental, quantitative understanding of the molecular mechanisms underlying the recalcitrance lignocellulosic biomass fine structure to enzymatic attack. The second objective is to establish relationships between cell wall component composition and molecular structural organization with hydrolysis processing conditions and correlate these relationships to biomass deconstruction efficiency. The third objective is to develop a mechanistic modeling framework capable of simulating biomass deconstruction under realistic hydrolysis conditions with comprehensive consideration of substrate morphology and component distribution. These objectives will be enabled through single-molecule imaging via Atomic Force Microscopy (AFM) and chemical imaging via Stimulated Raman Scattering (SRS) of the biomass deconstruction process during enzymatic treatment. Outcomes from the proposed research will enable the rational design of enzyme cocktails and processing conditions to overcome the factors that slow down the hydrolytic reactions, leading to optimal design of the hydrolysis bioreactor systems and cost reduction of cellulosic biofuel manufacturing systems.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Ankathi, S.K., Zhou, W., Webber, J.B.W., Patil, R., Chaudhari, U., Shonnard, D.R. "Synergistic effects between hydrolysis time and microporous structure in poplar" ACS Sustainable Chemistry and Engineering , v.7 , 2019 , p.12920 DOI: 10.1021/acssuschemeng.9b01926
Ankathi, S.K., Zhou, W., Webber, J.B.W., Patil, R., Chaudhari, U., Shonnard, D.R. "Synergistic effects between hydrolysis time and microporous structure in poplar" ACS Sustainable Chemistry and Engineering , v.7 , 2019 , p.12920 https://doi.org/10.1021/acssuschemeng.9b01926
Ankathi, S.K., Zhou, W., Webber, J.B.W., Patil, R., Chaudhari, U., Shonnard, D.R. "Synergistic effects between hydrolysis time and microporous structure in poplar" ACS Sustainable Chemistry and Engineering , v.7 , 2019 , p.12920

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

The research goals of this project are to enhance the efficiency of renewable biofuel production from renewable woody biomass and provide potential paths to successful commercialization of advanced biofuels.

Specifically, this project's objectives were to

1) improve our fundamental understanding of molecular mechanism of biomass recalcitrance to enzymatic attack,

2) to gain new insights into the relationships between cell wall component compositions, molecular structural organization/positioning, hydrolysis operation and design, and biomass deconstruction efficiency, and

3) to develop a sophisticated, mechanistic model capable of handling real lignocellulosic biomass hydrolysis with comprehensive consideration of biomass morphology and component distribution.

The main findings of this project include

1. Higher glucan and xylen sugar yields were measured for samples subjected to increasing severity of AFEX pretreatment under the enzymatic hydrolysis conditions (T, pH, enzyme loading). 

2. Using the NMR Cryoporomometry (NMRC) technique, biomass total pore volume decreases with increasing AFEX pretreatment, consistent with prior macroscopic measurement of densification of stover biomass with AFEX treatment.  Pore size distribution shifts to larger pore size upon increasing enzymatic hydrolysis severity.  

3. A multi-scale and multi-phase diffusion-adsorption-kinetics model successfully predicted transient enzyme diffusion and adsorption within biomass particles, and predicted sugar yields versus time at the macro-scale.  The model correctly predicted characteristic times for diffusion and adsorption of enzymes into biomass particles at the sub-millimeter scale and matched kinetics of sugar production at the flask bulk fluid scale. 

The NMRC measurements provided insights on how the microporous structure of corn stover evolves as a result of AFEX pretreatment and enzymatic hydrolysis.  The modeling research contributed to understanding of characteristic times for diffusion and adsorption of hydrolytic enzymes into biomass particles, effects of microporous structure (porosity and accessibility) on transport and hydrolysis, and combined models at multiple scales (particle scale with bulk reactor scale).  

Three graduate students were supported on this project and several undergraduate researchers.  We engaged with a UK researcher who contributed unique analytical capabilities to the project.  One PhD candidate graduated and joined Argonne National Laboratory as a postdoc.  One MS student graduated and joined a PhD program at another school.  A third graduate student continues PhD research toward completion by 2023 with support on another grant. 

Three peer-reviewed research articles were published or are in review and conference presentations showing research progress were presented.  

 

 



Last Modified: 12/27/2021
Modified by: David R Shonnard

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