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Multi-Scale Visualization of Dynamic Changes in Poplar Cell Walls During Alkali Pretreatment

Published online by Cambridge University Press:  19 February 2014

Zhe Ji ,
Jianfeng Ma  and
Feng Xu
Zhe Ji
Affiliation:
Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China
Jianfeng Ma
Affiliation:
Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China
Feng Xu*
Affiliation:
Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China
*
*Corresponding author. xfx315@bjfu.edu.cn
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Abstract

Alkali pretreatment is a promising pretreatment technology that can effectively deconstruct plant cell walls to enhance sugar release performance. In this study, multi-scale visualization of dynamic changes in poplar cell walls during sodium hydroxide pretreatment (2% w/v, 121°C) was carried out by light microscopy (LM), confocal Raman microscopy (CRM) and atomic force microscopy (AFM). LM observations indicated that swelling occurred primarily in the secondary wall (S) but alkali had little effect on the cell corner middle lamella (CCML). Correspondingly, there was a preferential delignification in the S at the beginning of pretreatment, while the level of delignification in CCML (~88%) was higher than that in the S (~83%) for the whole process revealed by Raman spectra. It also suggested that prolonging residence time to 180 min would not remove lignin completely but cause rapid loss of carbohydrates, which was further visualized by Raman spectroscopy images. Furthermore, AFM measurements illustrated that pretreatment with alkali exposed the embedded microfibrils from noncellulosic polymers clearly, enlarged the diameter of microfibrils, and decreased the surface porosity. These results suggested that there was a synergistic mechanism of lignocellulose deconstruction regarding cell wall swelling, main components dissolution, and microfibril morphological changes that occurred during alkali pretreatment.

Keywords

poplar cell wallalkali pretreatmentconfocal Raman microscopyatomic force microscopylignin
Type
Biological Applications
Information
Microscopy and Microanalysis , Volume 20 , Issue 2 , April 2014 , pp. 566 - 576
Copyright
© Microscopy Society of America 2014 

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Footnotes

†

Current address: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, 100083 Tsinghua East Road, Beijing, China.

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