Visualizing plant cell wall changes proves the superiority of hydrochloric acid over sulfuric acid catalyzed γ-valerolactone pretreatment

Journal Article · Fri Jan 01 00:00:00 UTC 2021 · Chemical Engineering Journal

DOI: https://doi.org/10.1016/j.cej.2021.128660 · OSTI ID:1755189

Zhang, Jian ^[1]; Shen, Wei ^[2]; Collings, Cynthia ^[2]; Vander Meulen, Kirk A. ^[3]; Fox, Brian G. ^[3]; Vázquez Ramos, Leida M. ^[3]; Dumesic, James A. ^[3]; Ding, Shi-You ^[2]

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1. Michigan State Univ., East Lansing, MI (United States); Michigan State University
2. Michigan State Univ., East Lansing, MI (United States)
3. Univ. of Wisconsin, Madison, WI (United States)

Thermochemical pretreatment is one of the key steps to process lignocellulosic biomass for production of biofuels and biomaterials. γ-valerolactone (GVL) has been used as a green and renewable solvent to efficiently dissolve lignin under acidic conditions and enhance subsequent enzyme digestibility. Further improvement is still required to lower the pretreatment temperature in order to reduce sugar degradation and irreversible lignin condensation, as well as the capital cost. In this study, we compared the use of HCl and H₂SO₄ as catalysts during GVL pretreatment, and found the performance of GVL-HCl at 100 °C was comparable to that of GVL-H₂SO₄ at 120 °C in terms of xylan and lignin removal and enzyme digestibility. We further monitored the lignin removal and cellulose accessibility in the cell walls at different pretreatment time points by imaging the changes in lignin auto-fluorescence and in CtCBM3-GFP binding with confocal laser scanning microscopy (CLSM), respectively. We found GVL-HCl pretreatment at a relative low temperature (100 °C) could rapidly remove lignin in the compound middle lamella and cell corner areas, which concurred with the increase of CtCBM3-GFP binding in these areas. Real-time imaging of cell wall degradation by cellulases further revealed that the secondary cell walls could be digested from both cell lumen and CML sides, and eventually fully deconstructed within 24 h. Furthermore, our results provide new insight into the effects of chloride anions on plant cell wall structure during GVL pretreatment, and offer potential routes to further optimize and enhance the efficiency of GVL-based pretreatment.

• Research Organization: Michigan State Univ., East Lansing, MI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0018409; SC0019072
• OSTI ID: 1755189
• Journal Information: Chemical Engineering Journal, Journal Name: Chemical Engineering Journal Vol. 412; ISSN 1385-8947
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English