Microscopy and Microanalysis

Biological Applications

Raman Microspectroscopy Imaging Study on Topochemical Correlation Between Lignin and Hydroxycinnamic Acids in Miscanthus sinensis

Jianfeng Maa1, Xia Zhoua1, Jing Maa1, Zhe Jia1, Xun Zhanga1 and Feng Xua1 c1

a1 Beijing Key Laboratory of Lignocellulosic Chemistry, Institute of Material Science and Technology, Beijing Forestry University, 100083 Beijing, China

Abstract

Confocal Raman microspectroscopy (CRM) has emerged as a powerful approach to visualize the compositional distribution in lignocellulosic biomass of cell walls. In this work, the applicability of CRM for imaging the topochemical correlation between lignin and hydroxycinnamic acids (HCA) in the Miscanthus sinensis internode was explored. Model compound [p-coumaric acid (PCA) and ferulic acid (FA)] analysis indicated that the band region from 1,152 to 1,197 cm−1 can be used to characterize the distribution of HCA. Raman images calculated by integrating over the area intensity of characteristic spectral regions showed heterogeneous distribution of lignin and HCA at cellular and sub-cellular level. When overlaying the Raman image of lignin and HCA distribution, it was found that these two polymers were co-located in the middle lamella and secondary wall of corresponding cells. Raman images for the band intensity ratio (1,173 cm−1/1,603 cm−1) indicated a clear association between lignin and HCA distribution within morphologically distinct cell wall layers of sclerenchyma fibers and the parenchyma. This is the first time that the spatial correlation between lignin and HCA concentration has been illustrated by a microspectroscopy imaging approach. The results are of importance in extending the current understanding of lignin and aromatics topochemistry in herbaceous biomass.

(Received November 18 2013)

(Accepted March 04 2014)

Key words

  • confocal Raman microspectroscopy;
  • Miscanthus sinensis ;
  • lignin;
  • hydroxycinnamic acids

Correspondence

c1 Corresponding author. xfx315@bjfu.edu.cn