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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.


XRD patterns of samples used in this study and relative comparison with amorphous cellulose (Na CMC).
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Figure 3: XRD patterns of samples used in this study and relative comparison with amorphous cellulose (Na CMC).

Mentions: The XRD patterns of untreated and IL-pretreated woodchips and forestry residues as well as an amorphous control sample of sodium carboxymethyl cellulose (Na CMC) are shown in Figure 3. Because the biomass used in this study contained lignin and hemicellulose, crystallinity index (CrI) values can only be interpreted as relative comparisons. The untreated woodchips and forestry residue samples are crystalline with CrI values of 34% and 30%, respectively and show diffraction profiles characteristic of the cellulose I polymorph, with three major peaks at 35, 22 and 15-16° 2θ, corresponding to the [004], [200] and combined [110] + [1-10] lattice places, respectively. The most intense reflection (200) for the two untreated samples is observed at 22.3° (woodchips) and 22.1° 2θ (forestry residues). Upon IL pretreatment, the recovered biomass gave XRD patterns displaying significantly less ordered cellulose structures, as compared to the untreated samples. The major peaks at 22.3 and 22.1° 2θ shift to lower 2θ values (larger d-spacing). The combined peak at around 15-16° 2θ, as well as the peak corresponding to the [004] lattice plane in cellulose I at around 35° 2θ were reduced to undetectable levels. The only exception seems to be the forestry residue sample pretreated at 120°C, which displays a broad feature, centered around 16° 2θ. The major peaks in the XRD patterns of the woodchips and forest residue samples pretreated at 120°C are found around 21.0 and 21.8° 2θ; the corresponding peaks for the samples treated with IL at 160°C are shifted to 20.2 and 20.9° 2θ. The shifted position and distorted shape of the major reflection (200) in the IL-treated samples suggest that the cellulose structure is significantly distorted. The occurrence of a broad peak at about 12.5° 2θ in the XRD pattern of the woodchips sample pretreated at 160°C seems to indicate that small amounts of cellulose II may also be present. However, no such peak was detected in the XRD pattern of the 160°C IL treated forestry residue sample, suggesting the content of cellulose II in that material is extremely low or nonexistent [26].


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)

XRD patterns of samples used in this study and relative comparison with amorphous cellulose (Na CMC).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: XRD patterns of samples used in this study and relative comparison with amorphous cellulose (Na CMC).
Mentions: The XRD patterns of untreated and IL-pretreated woodchips and forestry residues as well as an amorphous control sample of sodium carboxymethyl cellulose (Na CMC) are shown in Figure 3. Because the biomass used in this study contained lignin and hemicellulose, crystallinity index (CrI) values can only be interpreted as relative comparisons. The untreated woodchips and forestry residue samples are crystalline with CrI values of 34% and 30%, respectively and show diffraction profiles characteristic of the cellulose I polymorph, with three major peaks at 35, 22 and 15-16° 2θ, corresponding to the [004], [200] and combined [110] + [1-10] lattice places, respectively. The most intense reflection (200) for the two untreated samples is observed at 22.3° (woodchips) and 22.1° 2θ (forestry residues). Upon IL pretreatment, the recovered biomass gave XRD patterns displaying significantly less ordered cellulose structures, as compared to the untreated samples. The major peaks at 22.3 and 22.1° 2θ shift to lower 2θ values (larger d-spacing). The combined peak at around 15-16° 2θ, as well as the peak corresponding to the [004] lattice plane in cellulose I at around 35° 2θ were reduced to undetectable levels. The only exception seems to be the forestry residue sample pretreated at 120°C, which displays a broad feature, centered around 16° 2θ. The major peaks in the XRD patterns of the woodchips and forest residue samples pretreated at 120°C are found around 21.0 and 21.8° 2θ; the corresponding peaks for the samples treated with IL at 160°C are shifted to 20.2 and 20.9° 2θ. The shifted position and distorted shape of the major reflection (200) in the IL-treated samples suggest that the cellulose structure is significantly distorted. The occurrence of a broad peak at about 12.5° 2θ in the XRD pattern of the woodchips sample pretreated at 160°C seems to indicate that small amounts of cellulose II may also be present. However, no such peak was detected in the XRD pattern of the 160°C IL treated forestry residue sample, suggesting the content of cellulose II in that material is extremely low or nonexistent [26].

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.