Matrix-free hydrodynamic study on the size distribution and conformation of three technical lignins from wood and non-wood

Qushmua E Alzahrani,Tabot M.D Besong,Richard A Harding,Richard B Gillis,Richard J.A Gosselink,Emily Fong,Jan E.G Van Dam,Stephen E Harding,Gary G Adams,M Samil Kök,Arthur J Rowe

doi:10.1515/hf-2014-0318

Qushmua E Alzahrani, Tabot M.D Besong + Show 9 more

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https://doi.org/10.1515/hf-2014-0318

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Journal: Holzforschung	Publication Date: May 13, 2015
Citations: 7	License type: cc-by

Affiliation: University of Nottingham

Abstract

Abstract Molecular weight (MW) and related conformational data of three commercially available technical lignins (Alcell L, kraft L, and soda L) have been studied by means of analytical ultracentrifugation, taking advantage of some recent developments in both sedimentation velocity and sedimentation equilibrium determinations. The lignins were dissolved in dimethyl sulphoxide (with ca. 90% solubility), and solutions were studied with regards to their oligomeric state, heterogeneity profiles (distribution of sedimentation coefficients), and molecular weight distributions (MWD). Alcell L and soda L have similar properties showing one major low MW component and two minor high MW components, whereas kraft L appears to be larger and more uniform, i.e., it shows a more monodisperse MWD. Weight average molecular weight (M w) data from sedimentation equilibrium obtained by the new SEDFIT-MSTAR procedure in conjunction with MULTISIG analysis were found to be ~18 kDa (Alcell L), 25 kDa (kraft L), and 15 kDa (soda L). Further analysis of the data by means of the routines MULTISIG and M_INVEQ confirmed the presence of additional components in Alcell L and soda L, and the larger size and high degree of monodispersity of kraft L. The intrinsic viscosity data of the three lignins were found to be very similar in the range of 22–24 ml g-1, and all data were consistent with an elongated plate shape molecular structure with an equivalent discoid aspect ratio ~30.

Highlights

Lignins are a class of natural, highly branched phenylpropanoid macromolecules that have a random and amorphous three-dimensional structure, in which the partly cross-linked chains are hydrophobic, heterogeneous, and polydisperse
The aim of the present study is the determination of Molecular weight (MW)-related data of three technical lignins from different sources, which have been solubilised in dimethyl sulphoxide (DMSO)
Sedimentation velocity in the analytical ultracentrifuge (Figure 1) shows that all three lignins have a distribution of s, which are broad for Alcell L and soda L but narrow for kraft L

Summary

Introduction

Lignins are a class of natural, highly branched phenylpropanoid macromolecules that have a random and amorphous three-dimensional structure, in which the partly cross-linked chains are hydrophobic, heterogeneous, and polydisperse. The carbon content of the aromatic lignins is around 60–63%, i.e., higher than that of the accompanying polysaccharides (Sarkanen and Ludwig 1971; Fengel and Wegener 1984). Lignins are classified according to the composition of the three major phenylpropan units, namely 4-hydroxy-, guaiacyl-, and syringyl-type phenylpropanes, abbreviated as H, G, and S units, respectively. There are in essence G-lignins (in softwoods), GS-lignins (in hardwoods), and HGS lignins (in grasses) (Sarkanen and Ludwig 1971; Fengel and Wegener 1981; Zhong and Ye 2007; Vanholme et al 2010). Lignins are available either as an alkaline aqueous solution or in isolated powder form (Käuper 2004). Alcell L (and organosolv type L), kraft L ( called sulphate L), and soda L ( called alkali L) are three examples of Brought to you by | University of Oslo Norway Authenticated

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