Structural features of alternative lignin monomers associated with improved digestibility of artificially lignified maize cell walls

Journal Article · 13 March 2019 · Plant Science

DOI: https://doi.org/10.1016/j.plantsci.2019.02.004 · OSTI ID:1546966

Grabber, John H.  ^[1]; Davidson, Christy  ^[2]; Tobimatsu, Yuki  ^[2]; Kim, Hoon ^[2]; Lu, Fachuang ^[2]; Zhu, Yimin ^[2]; Opietnik, Martina ^[2]; Santoro, Nicholas ^[3]; Foster, Cliff E.  ^[3]; Yue, Fengxia ^[2]; Ress, Dino ^[4]; Pan, Xuejun  ^[5]; Ralph, John  ^[4]

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1. US Dept. of Agriculture (USDA), Madison, WI (United States). Agricultural Research Service (ARS)
2. Univ. of Wisconsin, Madison, WI (United States). Dept. of Biochemistry, and D.O.E. Great Lakes Bioenergy Research Center, Wisconsin Energy Inst.
3. Michigan State Univ., East Lansing, MI (United States). D.O.E. Great Lakes Bioenergy Research Center
4. Department of Biochemistry, and D.O.E. Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin, Madison, WI, USA
5. Department of Biological Systems Engineering, University of Wisconsin, Madison, WI, USA

Plant biologists are seeking new approaches for modifying lignin to improve the digestion and utilization of structural polysaccharides in crop cultivars for the production of biofuels, biochemicals, and livestock. To identify promising targets for lignin bioengineering, we artificially lignified maize (Zea mays L.) cell walls with normal monolignols plus 21 structurally diverse alternative monomers to assess their suitability for lignification and for improving fiber digestibility. Lignin formation and structure were assessed by mass balance, Klason lignin, acetyl bromide lignin, gel-state 2D-NMR and thioacidolysis procedures, and digestibility was evaluated with rumen microflora and from glucose production by fungal enzymes following mild acid or base pretreatments. Highly acidic or hydrophilic monomers proved unsuitable for lignin modification because they severely depressed cell wall lignification. By contrast, monomers designed to moderately alter hydrophobicity or introduce cleavable acetal, amide, or ester functionalities into the polymer often readily formed lignin, but most failed to improve digestibility, even after chemical pretreatment. Fortunately, several types of phenylpropanoid derivatives containing multiple ester-linked catechol or pyrogallol units were identified as desirable genetic engineering targets because they readily formed wall-bound polymers and improved digestibility, presumably by blocking cross-linking of lignin to structural polysaccharides and promoting lignin fragmentation during mild acidic and especially alkaline pretreatment.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States). Great Lakes Bioenergy Research Center
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0018409
• OSTI ID: 1546966
• Journal Information: Plant Science, Vol. 287; ISSN 0168-9452
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English