WAYS TO TAILOR-MAKE XYLAN FOR KRAFT PULPING
Genetic manipulation of trees in order to produce raw material with different chemical composition, which will perform better in pulping and bleaching, has gained large interest the last decade. Most efforts have been on increasing cellulose content, and modifying the lignin structure so that the pulping will be more efficient. Less interest has been focused on the hemicellulose structures, although many important chemical reactions occur on hemicelluloses during kraft pulping. For instance, hexenuronic acid is formed from 4-O-methyl glucuronic acid, a side group on xylan. This structure is a main contributor to the kappa number in the unbleached pulp, especially in hardwoods, and requires relatively strong bleaching agents for efficient removal. Remaining hexenuronic acid in the bleached pulp may furthermore cause post yellowing. In model experiments, we have simulated kraft cooking, and shown that hexenuronic acid is formed to a much lower degree from unmethylated glucuronic acid, than from 4-O-methylglucuronic acid. A tree without methyl groups on its glucuronic acid residues on xylan, is therefore expected to be pulped to a much lower kappa number, and to be easy to bleach to high brightness stability. According to a literature study, the possibilities to make such a tree by genetically manipulation appear to be promising. There might also be other ways, in which hemicelluloses structure can be manipulated.
β-elimination hexenuronic acid kraft pulping 4-O-metyl glucuronic acid transgenetic trees
Gunnar Henriksson Jiebing Li Chao Shi Mikael E. Lindstr(o)m
Wallenberg Wood Science Centre, School of Chemistry, Royal Institute of Technology, KTH, 100 44 Stockholm, Sweden
国际会议
16th International Symposium on Wood,Fiber and Pulping Chemistry(第十六届木材、纤维及制浆化学国际会议)
天津
英文
596-599
2011-06-08（万方平台首次上网日期，不代表论文的发表时间）