An environmental-friendly steam explosion process of bamboo chips followed with alkali and alkaline ethanol post-treatment (EP-A/AE process) was developed to produce bioethanol efficiently. This biorefinery process allows all major components of biomass being converted into high value added products. As a first part of series study, the chemical and structural features of the isolated lignin fractions were comparatively investigated by HPAEC, GPC, FT-IR, 2D HSQC and 31P NMR spectroscopies, as well as antioxidant activity analysis. It was found that the lignins contained low contents of carbohydrates (0.55-1.76%), and showed low molecular weights (780-1050 g/mol) together with narrow polydispersities (Mw/Mn, 1.48-1.84). This suggested that EP-A/AE process produced relatively pure and high-quality lignins which are suitable for further applications. For each steam-exploded sample, as compared to alkaline ethanol-extracted lignins, alkali-extracted lignins presented higher phenolic-OH, carboxylic-OH, pCA/FA ratios, and S/G ratios. HSQC NMR spectra revealed that bamboo lignin mainly consisted of �-O-4' combined with small amounts of �-�', �-5', and a, �-diaryl ethers linkages. Antioxidant activity investigation indicated that the radical scavenging index (RSI) of fractionated lignins (5.00-8.33) was much higher than that of BHT (0.22) but lower than that of BHA (12.5), suggesting that the biorefinery process is a promising method to fractionate lignin with good antioxidant activity for potential application in food industry.

Structure and antioxidant activities of alkaline lignins from steam exploded bamboo chips

247th National Meeting (2014)

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