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Insights into plant cell wall structure, architecture, and integrity using glycome profiling of native and AFEXTM-pre-treated biomass.

Pattathil S, Hahn MG, Dale BE, Chundawat SP - J. Exp. Bot. (2015)

Bottom Line: For most biomass types analysed, such loosening was also evident for other major non-cellulosic components including subclasses of pectin and xyloglucan epitopes.The studies also demonstrate that AFEX™ pre-treatment significantly reduced cell wall recalcitrance among diverse phylogenies (except softwoods) by inducing structural modifications to polysaccharides that were not detectable by conventional gross composition analyses.It was found that monitoring changes in cell wall glycan compositions and their relative extractability for untreated and pre-treated plant biomass can provide an improved understanding of variations in structure and composition of plant cell walls and delineate the role(s) of matrix polysaccharides in cell wall recalcitrance.

View Article: PubMed Central - PubMed

Affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA siva@ccrc.uga.edu shishir.chundawat@rutgers.edu.

No MeSH data available.


Enzymatic saccharification yields of untreated and AFEX™-pre-treated (for low, medium, and high severity) grasses, dicots, and gymnosperms. Total glucan-to-glucose yields after 24h and 168h are shown in white and red bars, respectively. Total xylan-to-xylose yields after 24h and 168h are shown in grey and blue bars, respectively. Error bars depict standard deviations of data from the mean values reported for assays conducted in triplicate.
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Figure 7: Enzymatic saccharification yields of untreated and AFEX™-pre-treated (for low, medium, and high severity) grasses, dicots, and gymnosperms. Total glucan-to-glucose yields after 24h and 168h are shown in white and red bars, respectively. Total xylan-to-xylose yields after 24h and 168h are shown in grey and blue bars, respectively. Error bars depict standard deviations of data from the mean values reported for assays conducted in triplicate.

Mentions: The composition of AFEX™-treated biomass has been shown previously to be identical to the composition of untreated samples, since this pre-treatment method is a dry-to-dry process and does not modify the gross cell wall composition (Chundawat et al., 2010, 2011b). Furthermore, as shown previously by Wyman and co-workers (Demartini et al., 2011), wet chemistry-based gross cell wall compositional data provide very little information on the ultrastructural modifications within pre-treated plant cell walls that influence its enzymatic deconstruction. Enzymatic saccharification of untreated and AFEX™-pre-treated monocots, woody dicots, herbaceous dicots, and softwoods for 24h and 168h led to a range of glucose (~5–91%) and xylose (~3–64%) yields, as shown in Fig. 7. In all cases, the most severe AFEX™ pre-treatment condition and 168h saccharification time period led to the highest sugar yields compared with the respective untreated samples. The severe AFEX™-pre-treated monocot grasses yielded ~80–90% total available glucan as glucose and 50–55% total available xylan as xylose. The lower hemicellulose conversion for AFEX™-treated samples is not unexpected considering that most commercially available cellulolytic enzyme cocktails (such as C.Tec2 used in this study) lack significant quantities of hemicellulolytic enzymes (Chundawat et al., 2011c). This is further indicated by poor arabinose yield (<20% of the theoretical maximum available; data not shown), which suggests that a significant fraction of the arabinoxylans and/or arabinogalactans in pre-treated monocots and dicots have not been enzymatically hydrolysed. Inclusion of additional hemicellulases has been shown to boost overall hemicellulose conversion further for AFEX™-treated lignocellulosic biomasses (Gao et al., 2010a, b, 2011). Nevertheless, the overall glucose and xylose yields obtained after prolonged saccharification time periods should be correlated with the relative accessibility of cell wall matrix polymers following AFEX™ pre-treatment. In general, the enzymatic hydrolysis yields for the monocots and hardwoods followed these trends: untreated<low severity AFEX™<<medium severity AFEX™<high severity AFEX™. However, both untreated and pre-treated softwoods yielded the lowest glucose/xylose yields (~10–25%), confirming the significant recalcitrance of these feedstocks to AFEX™ pre-treatment and enzymatic deconstruction compared with the other biomasses tested.


Insights into plant cell wall structure, architecture, and integrity using glycome profiling of native and AFEXTM-pre-treated biomass.

Pattathil S, Hahn MG, Dale BE, Chundawat SP - J. Exp. Bot. (2015)

Enzymatic saccharification yields of untreated and AFEX™-pre-treated (for low, medium, and high severity) grasses, dicots, and gymnosperms. Total glucan-to-glucose yields after 24h and 168h are shown in white and red bars, respectively. Total xylan-to-xylose yields after 24h and 168h are shown in grey and blue bars, respectively. Error bars depict standard deviations of data from the mean values reported for assays conducted in triplicate.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4493783&req=5

Figure 7: Enzymatic saccharification yields of untreated and AFEX™-pre-treated (for low, medium, and high severity) grasses, dicots, and gymnosperms. Total glucan-to-glucose yields after 24h and 168h are shown in white and red bars, respectively. Total xylan-to-xylose yields after 24h and 168h are shown in grey and blue bars, respectively. Error bars depict standard deviations of data from the mean values reported for assays conducted in triplicate.
Mentions: The composition of AFEX™-treated biomass has been shown previously to be identical to the composition of untreated samples, since this pre-treatment method is a dry-to-dry process and does not modify the gross cell wall composition (Chundawat et al., 2010, 2011b). Furthermore, as shown previously by Wyman and co-workers (Demartini et al., 2011), wet chemistry-based gross cell wall compositional data provide very little information on the ultrastructural modifications within pre-treated plant cell walls that influence its enzymatic deconstruction. Enzymatic saccharification of untreated and AFEX™-pre-treated monocots, woody dicots, herbaceous dicots, and softwoods for 24h and 168h led to a range of glucose (~5–91%) and xylose (~3–64%) yields, as shown in Fig. 7. In all cases, the most severe AFEX™ pre-treatment condition and 168h saccharification time period led to the highest sugar yields compared with the respective untreated samples. The severe AFEX™-pre-treated monocot grasses yielded ~80–90% total available glucan as glucose and 50–55% total available xylan as xylose. The lower hemicellulose conversion for AFEX™-treated samples is not unexpected considering that most commercially available cellulolytic enzyme cocktails (such as C.Tec2 used in this study) lack significant quantities of hemicellulolytic enzymes (Chundawat et al., 2011c). This is further indicated by poor arabinose yield (<20% of the theoretical maximum available; data not shown), which suggests that a significant fraction of the arabinoxylans and/or arabinogalactans in pre-treated monocots and dicots have not been enzymatically hydrolysed. Inclusion of additional hemicellulases has been shown to boost overall hemicellulose conversion further for AFEX™-treated lignocellulosic biomasses (Gao et al., 2010a, b, 2011). Nevertheless, the overall glucose and xylose yields obtained after prolonged saccharification time periods should be correlated with the relative accessibility of cell wall matrix polymers following AFEX™ pre-treatment. In general, the enzymatic hydrolysis yields for the monocots and hardwoods followed these trends: untreated<low severity AFEX™<<medium severity AFEX™<high severity AFEX™. However, both untreated and pre-treated softwoods yielded the lowest glucose/xylose yields (~10–25%), confirming the significant recalcitrance of these feedstocks to AFEX™ pre-treatment and enzymatic deconstruction compared with the other biomasses tested.

Bottom Line: For most biomass types analysed, such loosening was also evident for other major non-cellulosic components including subclasses of pectin and xyloglucan epitopes.The studies also demonstrate that AFEX™ pre-treatment significantly reduced cell wall recalcitrance among diverse phylogenies (except softwoods) by inducing structural modifications to polysaccharides that were not detectable by conventional gross composition analyses.It was found that monitoring changes in cell wall glycan compositions and their relative extractability for untreated and pre-treated plant biomass can provide an improved understanding of variations in structure and composition of plant cell walls and delineate the role(s) of matrix polysaccharides in cell wall recalcitrance.

View Article: PubMed Central - PubMed

Affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA siva@ccrc.uga.edu shishir.chundawat@rutgers.edu.

No MeSH data available.