Aggregates Formed During Biomass Pretreatment Stem from Both Hemicellulose and Lignin
12/16/2021
Small-angle neutron scattering (SANS) can be used to detect byproducts of biomass pretreatment. A reaction cell (A) holds a sample of pretreated switchgrass (brown center) during in situ SANS studies. The central sample chamber of the reaction cell is shown enlarged (B). [Reprinted with permission from Yang, et al. 2022. Structural Reorganization of Noncellulosic Polymers Observed In Situ During Dilute Acid Pretreatment by Small-Angle Neutron Scattering. ACS Sustainable Chem. Eng. 10 (1): 314-322. Copyright 2022 American Chemical Society.]
Production of second-generation bioethanol from lignocellulosic biomass requires pretreatment to open the plant cell wall structure and improve enzyme access. But lignin aggregates formed during dilute acid pretreatment (DAP) of biomass are known to contribute to lower sugar yields for biofuel production.
To understand the role of noncellulosic switchgrass polymers on the overall efficiency of pretreatment, researchers used time-resolved in situ small-angle neutron scattering (SANS) to investigate real-time structural changes in the noncellulosic polymers of switchgrass plant cell walls during DAP.
They found that hemicellulose forms aggregates between 80-130°C, whereas at higher temperatures lignin-derived aggregates are observed. The study provides the first direct evidence that early stages of pseudo-lignin aggregate formation within plant cell walls originate from hemicellulose, not just lignin, during thermochemical pretreatment and that both contribute to decreased enzyme accessibility and biomass recalcitrance.
Trends in the growth of lignin (blue) and pseudo-lignin (red) aggregate particles during dilute acid pretreatment. [Reprinted with permission from Yang, et al. 2022.]
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References
Yang, et al. 2022. Structural Reorganization of Noncellulosic Polymers Observed In Situ During Dilute Acid Pretreatment by Small-Angle Neutron Scattering. ACS Sustainable Chem. Eng. 10 (1): 314-322. [DOI: 10.1021/acssuschemeng.1c06276]