title: Isolation and structural characterization of lignin from  cotton stalk treated in an ammonia hydrothermal system.
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-0-4' 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.
authors.affiliation: Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing 100083, China. xm_zhang@bjfu.edu.cn
authors.forename: Sumin
authors.initials: S
authors.lastname: Kang
authors.forename: Lingping
authors.initials: L
authors.lastname: Xiao
authors.forename: Lingyan
authors.initials: L
authors.lastname: Meng
authors.forename: Xueming
authors.initials: X
authors.lastname: Zhang
authors.forename: Runcang
authors.initials: R
authors.lastname: Sun
mesh_terms: D000641:Ammonia / Q000737:chemistry; D002241:Carbohydrates / Q000737:chemistry; D005591:Chemical Fractionation; D003368:Gossypium / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry* / Q000302:isolation & purification*; D015394:Molecular Structure; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002241:Carbohydrates; D000641:Ammonia; D008031:Lignin