title: In situ label-free imaging of hemicellulose in plant cell walls using stimulated Raman scattering microscopy.
abstract: BACKGROUND
  Plant hemicellulose (largely xylan) is an excellent feedstock for renewable energy production and second only to cellulose in abundance. Beyond a source of fermentable sugars, xylan constitutes a critical polymer in the plant cell wall, where its precise role in wall assembly, maturation, and deconstruction remains primarily hypothetical. Effective detection of xylan, particularly by in situ imaging of xylan in the presence of other biopolymers, would provide critical information for tackling the challenges of understanding the assembly and enhancing the liberation of xylan from plant materials.
  
  
  RESULTS
  Raman-based imaging techniques, especially the highly sensitive stimulated Raman scattering (SRS) microscopy, have proven to be valuable tools for label-free imaging. However, due to the complex nature of plant materials, especially those same chemical groups shared between xylan and cellulose, the utility of specific Raman vibrational modes that are unique to xylan have been debated. Here, we report a novel approach based on combining spectroscopic analysis and chemical/enzymatic xylan removal from corn stover cell walls, to make progress in meeting this analytical challenge. We have identified several Raman peaks associated with xylan content in cell walls for label-free in situ imaging xylan in plant cell wall.
  
  
  CONCLUSIONS
  We demonstrated that xylan can be resolved from cellulose and lignin in situ using enzymatic digestion and label-free SRS microscopy in both 2D and 3D. We believe that this novel approach can be used to map xylan in plant cell walls and that this ability will enhance our understanding of the role played by xylan in cell wall biosynthesis and deconstruction.
authors.affiliation: Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory, PO Box 2008 MS6341, Oak Ridge, TN 37831 USA.
authors.forename: Yining
authors.identifier: 0000-0002-0202-2479
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory, PO Box 2008 MS6341, Oak Ridge, TN 37831 USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Yarbrough
authors.affiliation: Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Mittal
authors.affiliation: National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401 USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory, PO Box 2008 MS6341, Oak Ridge, TN 37831 USA.
authors.forename: Melvin P
authors.initials: MP
authors.lastname: Tucker
authors.affiliation: Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA.
authors.forename: Todd B
authors.initials: TB
authors.lastname: Vinzant
authors.affiliation: Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory, PO Box 2008 MS6341, Oak Ridge, TN 37831 USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Decker
authors.affiliation: Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA ; BioEnergy Science Center (BESC), Oak Ridge National Laboratory, PO Box 2008 MS6341, Oak Ridge, TN 37831 USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Himmel
keywords: Hemicellulose; Label-free imaging; Microscopy; Raman Spectroscopy; Stimulated Raman Scattering (SRS); Xylan; Xylanase