Structural features and antioxidant activities of degraded lignins from steam exploded bamboo stem

A two-step process based on steam explosion pretreatment and alkali/alkaline ethanol post-treatments of bamboo stems was developed to produce bioethanol efficiently. In this study, alkali/alkaline ethanol post-treatments were applied to isolate lignins from steam exploded (1.8 and 2.0 MPa for 5 min, and 2.0 MPa for 8 min) bamboo stems, which resulted in the dissolution of 28.9, 53.3 and 60.1% of acid-insoluble lignins, respectively. The structural features of the isolated lignins were comparatively and comprehensively investigated by FT-IR and NMR techniques. The lignins showed low molecular weights (M-w, 860-1190 g/mol), narrow polydispersities (M-w/M-n, 1.46-1.92), and high content of phenolic hydroxyl groups (0.53-1.79 mmol/g). Antioxidant activities investigation showed that the radical scavenging index (RSI) of the extracted lignins (2.02-5.56) was higher than BHT (0.19) but lower than that of BHA (11.11). The relatively high antioxidant activity of the lignins suggested that they may be a potential antioxidant in food and other industries. (C) 2014 Elsevier B.V. All rights reserved.