Structural changes to Pinus radiata wood lignin during kraft pulping and bleaching
type: CreativeWork
description: The aim of this thesis was to improve the quality of the information available concerning the structure of native (within wood) and residual (within pulps) lignins. A better understanding of the structure of lignin will assist the development of improved pulping and bleaching sequences. However, before this can be done, it is necessary to develop approaches to lignin isolation which provide more representative lignin samples without resorting to what are often very tedious extraction procedures. A key requirement for such isolation methods would be to isolate lignins in high yield with a structure as unmodified as possible. This would allow meaningful comparisons to be drawn with respect to structural changes occurring during the pulping and bleaching processes. An improved method for the isolation of lignin from Pinus radiata wood was developed. The method involves a three day enzymatic hydrolysis of ball milled wood, followed by a second ball milling stage. A combination of extraction and purification steps enables isolated yields of approximately 75% of the lignin present in the wood to be obtained. The key step is the second ball milling treatment, which allows essentially all the lignin in the enzyme digest residue to be extracted. The resulting cellulolytic enzyme lignins (CEL) contain approximately 5-8% carbohydrates and less than 2% protein. The CEL lignins, which were soluble in common lignin solvents, were characterised chemically and spectroscopically. They were shown to be remarkably similar to milled wood lignin (MWL) in terms of the total phenolic hydroxyl content, uncondensed β-O-4 ether content, and the distribution of interunit linkages, although there was some indication that the CEL lignins had a higher molecular weight than MWL. This shows that MWL, as far as a soluble lignin is concerned, is a reasonable representation of native lignin. However, the CEL method developed in this study is superior to the MWL method in that much higher yields of li…
abstract: The aim of this thesis was to improve the quality of the information available concerning the structure of native (within wood) and residual (within pulps) lignins. A better understanding of the structure of lignin will assist the development of improved pulping and bleaching sequences. However, before this can be done, it is necessary to develop approaches to lignin isolation which provide more representative lignin samples without resorting to what are often very tedious extraction procedures. A key requirement for such isolation methods would be to isolate lignins in high yield with a structure as unmodified as possible. This would allow meaningful comparisons to be drawn with respect to structural changes occurring during the pulping and bleaching processes. An improved method for the isolation of lignin from Pinus radiata wood was developed. The method involves a three day enzymatic hydrolysis of ball milled wood, followed by a second ball milling stage. A combination of extraction and purification steps enables isolated yields of approximately 75% of the lignin present in the wood to be obtained. The key step is the second ball milling treatment, which allows essentially all the lignin in the enzyme digest residue to be extracted. The resulting cellulolytic enzyme lignins (CEL) contain approximately 5-8% carbohydrates and less than 2% protein. The CEL lignins, which were soluble in common lignin solvents, were characterised chemically and spectroscopically. They were shown to be remarkably similar to milled wood lignin (MWL) in terms of the total phenolic hydroxyl content, uncondensed β-O-4 ether content, and the distribution of interunit linkages, although there was some indication that the CEL lignins had a higher molecular weight than MWL. This shows that MWL, as far as a soluble lignin is concerned, is a reasonable representation of native lignin. However, the CEL method developed in this study is superior to the MWL method in that much higher yields of li…
author: More, Nicole
license: https://researchcommons.waikato.ac.nz/bitstreams/5ff3dbd9-f60c-4bf1-b5b1-866b7c0481e7/download
date published: 1999
date modified: 2026-07-24T05:57:49Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato