Lignin molecules

No matter what its state is in the cell W all vivo, when the lignin molecule is released from its attachment to the cellulose matrix, either by breaking its tendril-like bonds (e.g. by pulping) or destruction of the cellulose matrix (c.g. by hydrolysis with acids or enzymes), it rolls up to a globular entangled mass something like tumbleweeds. 

The approaches adopted in attacking the lignin molecule can be divided into three categories oxidative, reductive and hydrolytic degradations. 

A sterically protected, water-soluble synthetic iron porphyrin could provide a readily available biomimetic catalyst for both basic research and potential industrial applications. Such a synthetic hemin might be superior to the enzyme, in that being a small molecule it could interact, with the polymeric lignin molecule more readily than can ligninase. 

The results of the molecular weight determination of the hydroxypropy-lated lignins by VPO are shown in Table I. It may be noted that for all samples, there was about a 20% increase in apparent molecular weights between freshly prepared solutions and those tested three days later. It is postulated that such an increase was due to a time dependent association of the hydroxypropylated lignin molecules in solution. 

The amount of small molecules in the permeate at low alkalinity increased with the relative concentration of small molecules (Figure 3). If hydrophobic bonding or simple solubility was the dominant mechanism for the association, the solubility of lignin molecules should be solely a function of pH regardless of the MWD of the parent solution. Consequently, the permeate MWD should be approximately the same and not a function of the MWD of the parent solution. Since the experimental permeate MWD varied with the parent MWD, the solubility or hydrophobic interaction mechanism was no longer accepted. 

The effectiveness of betaine can be explained better by its blocking proton uptake from solution. Betaine lessened the amount of protonated phenolic hydroxyl groups at any pH and consequently the intermolecular association between kraft lignin molecules. The chemical reactions can be shown as follows ... 

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