The methoxy group of beta-O-methyl glucuronic acid is central for the formation of hexenuronic acid during kraft pulping

• Hexenuronic acid is created from 4-O-methyl gluc-uronic acid – a side chain group in xylan, and one of the most important hemicelluloses in both hardwood and softwood - during alkaline conditions, such as kraft pulping. Especially in hardwood kraft pulp, hexenuronic acid corresponds to a large part of the kappa number, and the presence of this component in bleached pulp causes post yellowing. In this work it is shown that glucuronic acid that lacks a methoxy group on the 4-carbon does not form hexenuronic acid under alkaline condition to the same extent as 4-O-methylglucuronic acid. This opens up novel strategies for genetic modification of the hemicellulose structures in wood cultivated for kraft pulping.

Nyckelord

β-elimination

bleaching

hexenuronic acid

kraft pulping

transgenic tree

xylan

SRA - Molecular Bioscience

SRA - Molekylär biovetenskap

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