Alkaline-extracted lignin from Xylia xylocarpa and its antioxidant properties
2022
Karuna, Nardrapee | Namwong, Waleepatch | Ruaysoongnern, Natchaporn
The composition of Xylia xylocarpa (Roxb.) Taub. sawdust showed its potential to be used as a lignin source. It is composed of almost 40% lignin, 20% glucan and 10% hemicellulose. In this work, lignin in the sawdust was extracted with potassium hydroxide (KOH) in three different conditions: (1) 0.5% KOH for 10 minutes, (2) 0.5% KOH for 30 minutes and (3) 1.5% KOH for 30 minutes. Then, the lignin was precipitated by a two-step precipitation. The highest lignin content was extracted and recovered with a high purity of 96.1% from the 0.5% KOH for 10 minutes condition, whereas the 1.5% KOH condition gave less lignin content. The ferric-reducing antioxidant power (FRAP) showed no significant values of all samples. The IC₅₀ of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays showed that the lignin from the 1.5% KOH condition needed double compared to that of the other conditionsto neutralize DPPH for 50%. The Fourier transform infrared spectroscopy results confirmed that the extracted lignin was mainly composed of guaiacyl and syringyl alcohol and the severity of the pretreatment affected the deformation of bonds in the lignin. Therefore, this short (10 minutes) and low KOH (0.5%) method could reduce the cost in biomass conversion.
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