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Title: Syringyl lignin production in conifers: Proof of concept in a Pine tracheary element system

Conifers (softwoods) naturally lack syringyl units in their lignins, rendering lignocellulosic materials from such species more difficult to process than syringyl-rich hardwood species. Using a transformable Pinus radiata tracheary element (TE) system as an experimental platform, we investigated whether metabolic engineering can be used to create syringyl lignin in conifers. Pyrolysis-GC/MS and 2D-NMR analysis of P. radiata TE cultures transformed to express ferulate 5-hydroxylase (F5H) and caffeic acid O-methyltransferase (COMT) from Liquidambar styraciflua confirmed the production and incorporation of sinapyl alcohol into the lignin polymer. Transformation with F5H was sufficient for the production of syringyl lignin in TEs, but cotransformation with COMT improved its formation. In addition, lower levels of the pathway intermediate 5-hydroxyconiferyl alcohol were evidenced in cotransformation experiments, indicating that the introduction of the COMT overcame the inefficiency of the native pine methyltransferases for supporting sinapyl alcohol production. In conclusion, our results provide the proof of concept that it is possible to generate a lignin polymer that contains syringyl units in softwood species such as P. radiata, suggesting that it might be possible to retain the outstanding fiber properties of softwoods while imbuing them with the lignin characteristics of hardwoods that are more favorable for industrial processing.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2]
  1. Scion, Rotorua (New Zealand). Biotransformation Dept.
  2. Univ. of Wisconsin, Madison, WI (United States). Dept. of Biochemistry; The Wisconsin Energy Inst., Madison, WI (United States). US Dept. of Energy's Great Lakes Bioenergy Research Center
Publication Date:
Grant/Contract Number:
FC02-07ER64494
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 112; Journal Issue: 19; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Univ. of Wisconsin, Madison, WI (United States); Scion, Rotorua (New Zealand)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); Ministry for Business Innovation and Employment (New Zealand)
Contributing Orgs:
The Wisconsin Energy Inst., Madison, WI (United States)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; softwood; lignification; metabolic engineering; pulping; bioenergy
OSTI Identifier:
1235162
Alternate Identifier(s):
OSTI ID: 1348357