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Abstract Integrating multidisciplinary research in plant genetic engineering and renewable deep eutectic solvents (DESs) can facilitate a sustainable and economic biorefinery. Herein, we leveraged a plant genetic engineering approach to specifically incorporate C6C1monomers into the lignin structure. By expressing the bacterialubiCgene in sorghum,p‐hydroxybenzoic acid (PB)‐rich lignin was incorporated into the plant cell wall while this monomer was completely absent in the lignin of the wild‐type (WT) biomass. A DES was synthesized with choline chloride (ChCl) and PB and applied to the pretreatment of the PB‐rich mutant biomass for a sustainable biorefinery. The release of fermentable sugars was significantly enhanced (∼190 % increase) compared to untreated biomass by the DES pretreatment. In particular, the glucose released from the pretreated mutant biomass was up to 12 % higher than that from the pretreated WT biomass. Lignin was effectively removed from the biomass with the preservation of more than half of the β‐Ο‐4 linkages without condensed aromatic structures. Hydrogenolysis of the fractionated lignin was conducted to demonstrate the potential of phenolic compound production. In addition, a simple hydrothermal treatment could selectively extract PB from the same engineered lignin, showing a possible circular biorefinery. These results suggest that the combination of PB‐based DES and engineered PB‐rich biomass is a promising strategy to achieve a sustainable closed‐loop biorefinery.
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Producing high yield of levoglucosan by pyrolyzing nonthermal plasma-pretreated cellulose
Atmospheric pressure nonthermal plasma treatment can be a novel, green and low energy method to convert biomass to biobased chemicals. The unique physiochemistry of plasma discharge enables reactions within biomass that otherwise could not possibly occur under traditional conditions. In this study, we present a simple method of producing a high yield of levoglucosan from cellulose without using any catalysts, chemicals, solvents or vacuum, but by using plasma treatment to control the depolymerization mechanism of cellulose. Cellulose was first pretreated in a dielectric barrier discharge reactor operating in ambient air or argon for 10–60 s, followed by pyrolysis at 350–450 °C to produce up to 78.6% of levoglucosan. Without the plasma pretreatment, the maximum yield of levoglucosan from cellulose pyrolysis was 58.2%. The results of this study showed that the plasma pretreatment led to homolytic cleavage of glycosidic bonds. The resulting free radicals were then trapped within the cellulose structure when the plasma discharge stopped, allowing subsequent pyrolysis of the plasma-pretreated cellulose to proceed through a radical-based mechanism. The present results also revealed that although the radical-based mechanism is highly selective to levoglucosan formation, this pathway is usually discouraged when the untreated cellulose is pyrolyzed due to the high energy barrier for homolytic cleavage. Initiating homolytic cleavage during the plasma pretreatment also helped the pretreated cellulose to produce higher yields of levoglucosan using lower pyrolysis temperatures. At 375 °C, the levoglucosan yield was only 53.2% for the untreated cellulose, whereas the yield reached 77.6% for the argon-plasma pretreated cellulose.
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- Award ID(s):
- 1803823
- PAR ID:
- 10349604
- Date Published:
- Journal Name:
- Green Chemistry
- Volume:
- 22
- Issue:
- 6
- ISSN:
- 1463-9262
- Page Range / eLocation ID:
- 2036 to 2048
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d0gc00255k
