Studies on the Effect of Ball Milling on Lignin Structure Using a Modified DFRC Method

The structures of milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and residual lignin (REL) from a loblolly pine were analyzed using a modified derivatization followed by reductive cleavage (DFRC) method developed to allow the quantitative determination of three different structural mono...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2002-01, Vol.50 (1), p.129-135
Main Authors: Ikeda, Tsutomu, Holtman, Kevin, Kadla, John F, Chang, Hou-min, Jameel, Hasan
Format: Article
Language:English
Subjects:
Applied sciences
Chemistry, Organic - methods
Chromatography, Gas - methods
Exact sciences and technology
Lignin - chemistry
Lignin and derivatives
Molecular Structure
Natural polymers
Oxidation-Reduction
Physicochemistry of polymers
Pinus - chemistry
Plant Extracts - chemistry
Wood
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Summary:The structures of milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and residual lignin (REL) from a loblolly pine were analyzed using a modified derivatization followed by reductive cleavage (DFRC) method developed to allow the quantitative determination of three different structural monomeric products originating in lignin:  phenolic β-O-4, α-O-4, and etherified β-O-4 structures. Results show that MWL and CEL are structurally identical, with an increased phenolic β-O-4 content compared to that of the original Wiley milled wood. These results indicate that the portion of lignin linked to carbohydrates and that not linked to carbohydrates are structurally the same. Modified DFRC analysis of the effect of ball milling on the structure of lignin in wood, MWL, CEL, and REL indicate that vibratory ball milling does not change the lignin structure provided certain precautions are taken. Specifically, dry vibratory ball milling under a nitrogen atmosphere causes substantial structural changes including condensation, whereas vibratory ball milling in toluene had little effect on the lignin structure. This indicates that the structural differences observed in MWL and CEL arise because of the extraction procedure, which preferentially extracts phenolic lignin structures. MWL and CEL are representative of the total lignin in wood; however, due primarily to the solvent extraction process, higher phenolic hydroxyl contents are observed. Nitrobenzene oxidation showed structural results similar to those from the modified DFRC method. Keywords: Aryl ether bonds; milled wood lignin (MWL); cellulolytic enzyme lignin (CEL); ball milling; native lignin; structure
ISSN:0021-8561
1520-5118
DOI:10.1021/jf010870f