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Comparison of sugar content for ionic liquid pretreated Douglas-fir woodchips and forestry residues.

Socha AM, Plummer SP, Stavila V, Simmons BA, Singh S - Biotechnol Biofuels (2013)

Bottom Line: The development of affordable woody biomass feedstocks represents a significant opportunity in the development of cellulosic biofuels.X-ray diffraction (XRD) showed that the pretreated cellulose was less crystalline after IL pretreatment as compared to untreated control samples.These results indicate that forestry residues may be a more viable feedstock than previously thought for the production of biofuels.

View Article: PubMed Central - HTML - PubMed

Affiliation: Deconstruction Division, Joint BioEnergy Institute, 5885 Hollis Avenue, Emeryville, CA 94608, USA. ssingh@lbl.gov.

ABSTRACT

Background: The development of affordable woody biomass feedstocks represents a significant opportunity in the development of cellulosic biofuels. Primary woodchips produced by forest mills are considered an ideal feedstock, but the prices they command on the market are currently too expensive for biorefineries. In comparison, forestry residues represent a potential low-cost input but are considered a more challenging feedstock for sugar production due to complexities in composition and potential contamination arising from soil that may be present. We compare the sugar yields, changes in composition in Douglas-fir woodchips and forestry residues after pretreatment using ionic liquids and enzymatic saccharification in order to determine if this approach can efficiently liberate fermentable sugars.

Results: These samples were either mechanically milled through a 2 mm mesh or pretreated as received with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [C2mim][OAc] at 120°C and 160°C. IL pretreatment of Douglas-fir woodchips and forestry residues resulted in approximately 71-92% glucose yields after enzymatic saccharification. X-ray diffraction (XRD) showed that the pretreated cellulose was less crystalline after IL pretreatment as compared to untreated control samples. Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) revealed changes in lignin and hemicellulose structure and composition as a function of pretreatment. Mass balances of sugar and lignin streams for both the Douglas-fir woodchips and forestry residues throughout the pretreatment and enzymatic saccharification processes are presented.

Conclusions: While the highest sugar yields were observed with the Douglas-fir woodchips, reasonably high sugar yields were obtained from forestry residues after ionic liquid pretreatment. Structural changes to lignin, cellulose and hemicellulose in the woodchips and forestry residues of Douglas-fir after [C2mim][OAc] pretreatment are analyzed by XRD and 2D-NMR, and indicate that significant changes occurred. Irrespective of the particle sizes used in this study, ionic liquid pretreatment successfully allowed high glucose yields after enzymatic saccharification. These results indicate that forestry residues may be a more viable feedstock than previously thought for the production of biofuels.

No MeSH data available.


(A) Mass balance for Douglas-fir woodchip and (B) un-milled forestry residue pretreatments at 160°C.
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Figure 5: (A) Mass balance for Douglas-fir woodchip and (B) un-milled forestry residue pretreatments at 160°C.

Mentions: Nuclear Magnetic Resonance (NMR) studies of untreated Douglas-fir woodchips revealed lignin interunit, polysaccharide, acylated polysaccharide and anomeric resonances similar to pine [29]. Both untreated and IL pretreated Douglas-fir woodchips showed large cross peaks that can readily be assigned to lignin methoxyl groups δ (1H/13C) 3.73/55.4, and cellulose (δ 3.49-3.79/60.2, δ 3.37/74.3, δ 3.07/72.6) indicating that these polymers were not extensively removed during pretreatment (Figure 4). β-aryl ether crosspeaks at δ 4.73/71.0 and δ 4.27/83.8 as well as the phenylcoumaran (β-5) α resonance (δ 5.44/86.7) also appeared in both spectra indicating that these linkages remain intact during pretreatment. A series of correlations corresponding to minor components of Douglas-fir hemicellulose, such as those for xylan (δ 3.30/70.1), β-D- xylopyranosyl (δ 4.32/96.8), arabinan (δ 3.71/65.8), and α-L-arabinofuranosyl (δ 5.05/108.8) were absent from the spectrum of the pretreated material. Several additional hemicellulose resonances were assigned to mannan, the major hemicellulose component of Douglas-fir. For example, a 2-O-acyl-β-D-mannopyanosyl correlation (δ 5.38/70.6) was also absent from the pretreated biomass spectrum, while a second resonance assigned to 2-O-acyl-β-D-mannopyanosyl polymer (δ 4.77/98.6) was significantly decreased in the pretreated spectrum (Figure 5). Another large cross peak in the untreated spectrum that was missing from the pretreated material corresponded to the α-D-mannopyrosyl resonances at δ 4.88/92.5. Interestingly, the α -1 atom (δ 3.64/51.4), identified in Douglas-fir lignin by Berlin et al. [30], is clearly missing after pretreatment, suggesting scission of the bond in the α – 1 linkage occurs during pretreatment with [C2mim][OAc] at the conditions studied.


Comparison of sugar content for ionic liquid pretreated Douglas-fir woodchips and forestry residues.

Socha AM, Plummer SP, Stavila V, Simmons BA, Singh S - Biotechnol Biofuels (2013)

(A) Mass balance for Douglas-fir woodchip and (B) un-milled forestry residue pretreatments at 160°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672072&req=5

Figure 5: (A) Mass balance for Douglas-fir woodchip and (B) un-milled forestry residue pretreatments at 160°C.
Mentions: Nuclear Magnetic Resonance (NMR) studies of untreated Douglas-fir woodchips revealed lignin interunit, polysaccharide, acylated polysaccharide and anomeric resonances similar to pine [29]. Both untreated and IL pretreated Douglas-fir woodchips showed large cross peaks that can readily be assigned to lignin methoxyl groups δ (1H/13C) 3.73/55.4, and cellulose (δ 3.49-3.79/60.2, δ 3.37/74.3, δ 3.07/72.6) indicating that these polymers were not extensively removed during pretreatment (Figure 4). β-aryl ether crosspeaks at δ 4.73/71.0 and δ 4.27/83.8 as well as the phenylcoumaran (β-5) α resonance (δ 5.44/86.7) also appeared in both spectra indicating that these linkages remain intact during pretreatment. A series of correlations corresponding to minor components of Douglas-fir hemicellulose, such as those for xylan (δ 3.30/70.1), β-D- xylopyranosyl (δ 4.32/96.8), arabinan (δ 3.71/65.8), and α-L-arabinofuranosyl (δ 5.05/108.8) were absent from the spectrum of the pretreated material. Several additional hemicellulose resonances were assigned to mannan, the major hemicellulose component of Douglas-fir. For example, a 2-O-acyl-β-D-mannopyanosyl correlation (δ 5.38/70.6) was also absent from the pretreated biomass spectrum, while a second resonance assigned to 2-O-acyl-β-D-mannopyanosyl polymer (δ 4.77/98.6) was significantly decreased in the pretreated spectrum (Figure 5). Another large cross peak in the untreated spectrum that was missing from the pretreated material corresponded to the α-D-mannopyrosyl resonances at δ 4.88/92.5. Interestingly, the α -1 atom (δ 3.64/51.4), identified in Douglas-fir lignin by Berlin et al. [30], is clearly missing after pretreatment, suggesting scission of the bond in the α – 1 linkage occurs during pretreatment with [C2mim][OAc] at the conditions studied.

Bottom Line: The development of affordable woody biomass feedstocks represents a significant opportunity in the development of cellulosic biofuels.X-ray diffraction (XRD) showed that the pretreated cellulose was less crystalline after IL pretreatment as compared to untreated control samples.These results indicate that forestry residues may be a more viable feedstock than previously thought for the production of biofuels.

View Article: PubMed Central - HTML - PubMed

Affiliation: Deconstruction Division, Joint BioEnergy Institute, 5885 Hollis Avenue, Emeryville, CA 94608, USA. ssingh@lbl.gov.

ABSTRACT

Background: The development of affordable woody biomass feedstocks represents a significant opportunity in the development of cellulosic biofuels. Primary woodchips produced by forest mills are considered an ideal feedstock, but the prices they command on the market are currently too expensive for biorefineries. In comparison, forestry residues represent a potential low-cost input but are considered a more challenging feedstock for sugar production due to complexities in composition and potential contamination arising from soil that may be present. We compare the sugar yields, changes in composition in Douglas-fir woodchips and forestry residues after pretreatment using ionic liquids and enzymatic saccharification in order to determine if this approach can efficiently liberate fermentable sugars.

Results: These samples were either mechanically milled through a 2 mm mesh or pretreated as received with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [C2mim][OAc] at 120°C and 160°C. IL pretreatment of Douglas-fir woodchips and forestry residues resulted in approximately 71-92% glucose yields after enzymatic saccharification. X-ray diffraction (XRD) showed that the pretreated cellulose was less crystalline after IL pretreatment as compared to untreated control samples. Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) revealed changes in lignin and hemicellulose structure and composition as a function of pretreatment. Mass balances of sugar and lignin streams for both the Douglas-fir woodchips and forestry residues throughout the pretreatment and enzymatic saccharification processes are presented.

Conclusions: While the highest sugar yields were observed with the Douglas-fir woodchips, reasonably high sugar yields were obtained from forestry residues after ionic liquid pretreatment. Structural changes to lignin, cellulose and hemicellulose in the woodchips and forestry residues of Douglas-fir after [C2mim][OAc] pretreatment are analyzed by XRD and 2D-NMR, and indicate that significant changes occurred. Irrespective of the particle sizes used in this study, ionic liquid pretreatment successfully allowed high glucose yields after enzymatic saccharification. These results indicate that forestry residues may be a more viable feedstock than previously thought for the production of biofuels.

No MeSH data available.