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Isolation and Structural Characterization of Lignin from Cotton Stalk Treated in an Ammonia Hydrothermal System
Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing 100083, China
State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China
* Authors to whom correspondence should be addressed.
Received: 28 May 2012; in revised form: 7 November 2012 / Accepted: 13 November 2012 / Published: 16 November 2012
Abstract: To investigate the potential for the utilization of cotton stalk, ammonia hydrothermal treatment was applied to fractionate the samples into aqueous ammonia-soluble and ammonia-insoluble portions. The ammonia-soluble portion was purified to yield lignin fractions. The lignin fractions obtained were characterized by wet chemistry (carbohydrate analysis) and spectroscopy methods (FT-IR, 13C and 1H-13C HSQC NMR spectroscopy) as well as gel permeation chromatography (GPC). The results showed that the cotton stalk lignin fractions were almost absent of neutral sugars (0.43%–1.29%) and had relatively low average molecular weights (1255–1746 g/mol). The lignin fractions belonged to typical G-S lignin, which was composed predominately of G-type units (59%) and noticeable amounts of S-type units (40%) together with a small amount of H-type units (~1%). Furthermore, the ammonia-extractable lignin fractions were mainly composed of β-O-4' inter-unit linkages (75.6%), and small quantities of β-β' (12.2%), together with lower amounts of β-5' carbon-carbon linkages (7.4%) and p-hydroxycinnamyl alcohol end groups.
Keywords: cotton stalk; lignin; ammonia hydrothermal system; 13C NMR; HSQC
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MDPI and ACS Style
Kang, S.; Xiao, L.; Meng, L.; Zhang, X.; Sun, R. Isolation and Structural Characterization of Lignin from Cotton Stalk Treated in an Ammonia Hydrothermal System. Int. J. Mol. Sci. 2012, 13, 15209-15226.
Kang S, Xiao L, Meng L, Zhang X, Sun R. Isolation and Structural Characterization of Lignin from Cotton Stalk Treated in an Ammonia Hydrothermal System. International Journal of Molecular Sciences. 2012; 13(11):15209-15226.
Kang, Sumin; Xiao, Lingping; Meng, Lingyan; Zhang, Xueming; Sun, Runcang. 2012. "Isolation and Structural Characterization of Lignin from Cotton Stalk Treated in an Ammonia Hydrothermal System." Int. J. Mol. Sci. 13, no. 11: 15209-15226.