Lignin content versus syringyl to guaiacyl ratio amongst poplars

• Published in: Bioresource technology Vol. 100; no. 4; pp. 1628 - 1633
• Main Authors: Bose, Samar K., Francis, Raymond C., Govender, Mark, Bush, Tamara, Spark, Andrew
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2009; [New York, NY]: Elsevier Ltd; Elsevier
• Subjects: Biological and medical sciences; Copper - chemistry; cupric oxide; Fundamental and applied biological sciences. Psychology; hardwood; Hydrolysis; kraft pulping; lignin; Lignin - chemistry; Lignin content; Manganese Compounds - chemistry; nitrobenzene; Nitrobenzene oxidation; Nitrobenzenes - chemistry; oxidation; Oxidation-Reduction; Oxides - chemistry; Permanganate oxidation; Poplars; Populus; Populus - chemistry; potassium permanganate; pulp and paper technology; S:G ratio; Wood - chemistry; Lignin content; S:G ratio; Permanganate oxidation; Poplars; Nitrobenzene oxidation; Lignin; Salicaceae; Guaiacyl unit; Dicotyledones; Angiospermae; Tree; Spermatophyta; Oxidation; Syringyl unit; Populus
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2008.08.046

Two oxidation techniques that afford high yields of monomers and dimers were used to more accurately estimate the syringyl to guaiacyl (S:G) ratio of hardwood lignins. Permanganate oxidation of the woodmeal after a CuO pre-hydrolysis step gave poor results and this was attributed to preferential oxidation and degradation of syringyl nuclei by CuO. However, this procedure did provide a good estimate of the percentages of both S and G phenylpropane (C 9) units that were uncondensed. When the total S and G products from nitrobenzene oxidation (NBO) of the uncondensed fractions were corrected, credible S:G ratios were obtained. These ratios were in good agreement with results from KMnO 4 oxidation of dissolved kraft lignin without CuO pre-hydrolysis. The corrected NBO method was used to determine the S:G ratio of 13 poplars, and the values ranged from 1.01 to 1.68. Unlike results from other investigations, an excellent linear correlation ( R 2 = 0.846) was obtained for a decreasing lignin content (28% to 16.5%) with an increase in the S:G ratio.