Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/13/2008
Publication Date: 8/27/2008
Citation: Grabber, J. H., Ralph, J., Hatfield, R. D., Lu, F. 2008. Copolymerization of coniferyl ferulate with monolignols: impact on lignin formation and alkaline delignification of maize cell walls. Proceedings of Ferulate '08. p. 36. Interpretive Summary:
Technical Abstract: Incorporating alkali-labile (ester) interunit linkages into plant lignins could enhance fiber delignification during papermaking and improve the ruminal or industrial biofermentation of structural polysaccharides into organic acids, ethanol, or other products. In this model study, we examined how substitution of coniferyl alcohol (a normal monolignol) with 0 to 60% coniferyl ferulate (an ester conjugate from secondary metabolism) influenced the formation of lignin and the alkaline delignification and enzymatic hydrolysis of artificially lignified maize cell walls. Although extensively copolymerized into lignin, coniferyl ferulate accelerated peroxidase inactivation, interfered with cell-wall ferulate copolymerization into lignin, and slightly reduced the molecular weight and concentration of lignin in cell walls. Coniferyl ferulate incorporation increased the extractability of cell wall lignin by up to 2-fold in aqueous 0.5 M NaOH at 30, 100 and 160 ºC and it reduced the molecular weight of alkaline soluble lignins. Thus, the conjugate provides the option of producing alkaline-insoluble residues with substantially less non-cellulosic and lignin contamination or of delignifying cell walls at lower temperatures to increase fiber yields. Coniferyl ferulate incorporation also increased sugar yields at the onset of enzymatic hydrolysis by up to 45% and the final yield of sugars by up to 15% for lignified cell walls, both before and after a 30 °C pretreatment with 0.5 M NaOH. Based on our results, bioengineering of plants to incorporate coniferyl ferulate into lignin should reduce costs and enhance the effectiveness of lignocellulosic biomass saccharification and particularly pulping for paper production.