Characterization of Miscanthus giganteus Lignin Isolated by Ethanol Organosolv Process under Reflux Condition
详细信息 查看全文
- 作者：Stefan Bauer ; Hagit Sorek ; Valerie D. Mitchell ; Ana B. Ib谩帽ez ; David E. Wemmer
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2012
- 出版时间：August 22, 2012
- 年：2012
- 卷：60
- 期：33
- 页码：8203-8212
- 全文大小：492K
- 年卷期：v.60,no.33(August 22, 2012)
- ISSN：1520-5118
文摘
Miscanthus giganteus lignin was extracted by an organosolv process under reflux conditions (4 h) with varying concentrations of ethanol (65%, 75%, 85%, 95%) and 0.2 M hydrochloric acid as catalyst. The resulting lignin was extensively characterized by size exclusion chromatography (SEC), Fourier-transform infrared spectroscopy (FTIR), gas chromatography鈥搈ass spectrometry (GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR), and chemical analysis (residual sugars, Klason lignin, ash). The predominant linkage units present were 尾-O-4鈥?(82鈥?4%), resinol (6鈥?%), and phenylcoumaran (10鈥?1%). The 65% ethanol solvent system gave the lowest lignin yield (14% of starting biomass) compared to 29鈥?2% of the other systems. Increasing ethanol concentration resulted in decreasing carbohydrate content of the lignins (3.6鈥?.1%), a higher solubility in tetrahydrofuran (THF), a slight reduction of the molecular weight (Mw 2.72鈥?.25 KDa), an increasing 伪-ethoxylation, and an increase in ethoxylated phenylpropenoic compounds (p-coumaric and ferulic acid), but the S/G ratio of the monolignols (0.63, GC/MS) and Klason lignin content (86鈥?8%) were unaffected. An extraction method for these ethyl-esterified phenylpropenoids and smaller molecular weight lignin compounds was developed. The effect of reaction time (2, 4, and 8 h) was investigated for the 95% ethanol solvent system. Besides increased lignin yield (13鈥?3%), a slight increase in Mw (2.21鈥?.38 kDa) and S/G ratio (0.53鈥?.68, GC-MS) was observed. Consecutive extractions suggested that these changes were not from lignin modifications (e.g., condensations) but rather from extraction of lignin of different composition. The results were compared to similar solvent systems with 95% acetone and 95% dioxane.