Investigation of biomass degradation mechanism in pretreatment of switchgrass by aqueous ammonia and sodium hydroxide

• Published in: Bioresource technology Vol. 101; no. 21; pp. 8185 - 8191
• Main Authors: Gupta, Rajesh, Lee, Y.Y.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-11-2010; [New York, NY]: Elsevier Ltd; Elsevier
• Subjects: Ammonia; Ammonia - pharmacology; Biological and medical sciences; Biomass; Carbohydrates - analysis; Degradation; Fundamental and applied biological sciences. Psychology; H 2O 2; Lignin - isolation & purification; Liquids; NaOH; Oligomers; Poaceae - drug effects; Poaceae - growth & development; Poaceae - metabolism; Pretreatment; Sodium hydroxide; Sodium Hydroxide - pharmacology; Spectroscopy, Fourier Transform Infrared; Sugars; Switchgrass; Thermogravimetry; H 2O 2; NaOH; Ammonia; Pretreatment; Switchgrass; Monocotyledones; Hydrogen peroxide; H; Biomass; Panicum virgatum; Sodium hydroxide; O; Degradation; Gramineae; Aqueous medium; Angiospermae; Herbaceous plant; Spermatophyta
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2010.05.039

Pretreatment of switchgrass using aqueous ammonia or NaOH was investigated as a means to enhance the enzymatic digestibility. To increase the effectiveness of pretreatment, H
2O
2 was supplemented with the alkaline reagents. Since H
2O
2 is unstable at high temperature, low-to-high step-change of temperature was applied, and this scheme was found to be effective in the case of NH
3/H
2O
2 treatment. The composition of pretreatment liquid indicates that hemicellulose solubilized during alkaline treatment exists either in the form of oligomers or as lignin–carbohydrate complex (LCC). LCC formation was prominent in ammonia treatment and in NaOH/H
2O
2 treatment, and that LCC formation protects the hemicelluloses sugars from degradation. Lignin in the pretreatment liquor was precipitated and subjected to TGA and FTIR analyses. TGA data indicate that NaOH–lignin has more uniform structure and higher O/C ratio than ammonia–lignin. FTIR analysis indicates that NaOH–lignin has lower aromatic content but higher guaiacyl type structure than ammonia–lignin.