Toward a better understanding of the lignin isolation process from wood

Department of Forest Biomaterials Science and Engineering, College of Natural Resources, North Carolina State University, Raleigh, 27695-8005, USA.
Journal of Agricultural and Food Chemistry (Impact Factor: 3.11). 09/2006; 54(16):5939-47. DOI: 10.1021/jf060722v
Source: PubMed

ABSTRACT The recently developed protocol for isolating enzymatic mild acidolysis lignins (EMAL) coupled with the novel combination of derivatization followed by reductive cleavage (DFRC) and quantitative (31)P NMR spectroscopy were used to better understand the lignin isolation process from wood. The EMAL protocol is shown to offer access at lignin samples that are more representative of the overall lignin present in milled wood. The combination of DFRC/(31)P NMR provided a detailed picture on the effects of the isolation conditions on the lignin structure. More specifically, we have used vibratory and ball milling as the two methods of wood pulverization and have compared their effects on the lignin structures and molecular weights. Vibratory-milling conditions cause substantial lignin depolymerization. Lignin depolymerization occurs via the cleavage of uncondensed beta-aryl ether linkages, while condensed beta-aryl ethers and dibenzodioxocins were found to be resistant to such mechanical action. Condensation and side chain oxidations were induced mechanochemically under vibratory-milling conditions as evidenced by the increased amounts of condensed phenolic hydroxyl and carboxylic acid groups. Alternatively, the mild mechanical treatment offered by ball milling was found not to affect the isolated lignin macromolecular structure. However, the overall lignin yields were found to be compromised when the mechanical action was less intense, necessitating longer milling times under ball-milling conditions. As compared to other lignin preparations isolated from the same batch of milled wood, the yield of EMAL was about four times greater than the corresponding milled wood lignin (MWL) and about two times greater as compared to cellulolytic enzyme lignin (CEL). Molecular weight distribution analyses also pointed out that the EMAL protocol allows the isolation of lignin fractions that are not accessed by any other lignin isolation procedures.

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Available from: Ilari Filpponen, Aug 11, 2015
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    • "The residual lignin isolated from soda-AQ and k raft pulps cooked to kappa number 15 and 20 of the clone G1xUGL (isolated from the pulps by acidolysis) as well as the lignin precipitated from their respective black liquors were analyzed by two-dimensional nuclear magnetic resonance (2D-NMR). The isolation of MWL and their structural characteristics were compared to those of the milled wood lignin (MWL) isolated from the initial raw material, a lignin preparation that is still considered to be the representative of the native lignin in the plant, despite its limitations (Guerra et al., 2006; Rencoret et al., 2009). The isolation of MWL from wood of the eucalypt clone G1xUGL was previously described by Prinsen et al. (2012). "
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