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Chemistry and Industry of Forest Products ›› 2014, Vol. 34 ›› Issue (4): 90-96.doi: 10.3969/j.issn.0253-2417.2014.04.015

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Surface Chemical Structure of Alkali Lignin Modified by the Synergistic Process of Laccase and Ultrasound

LIAN Hai-lan1, CHENG Ming-juan1, HONG Shu1, ZHAN Xian-xu2   

  1. 1. College of Wood Science and Technology, Nanjing Forestry University, Nanjing 210037, China;
    2. Dehua TB Decoration Material Co., Ltd., Huzhou 313200, China
  • Received:2014-01-10 Online:2014-08-25 Published:2015-08-18

Abstract: Wheat alkali lignin was treated by ultrasound, laccase, and the synergistic process of ultrasound and lassase, respectively. The chemical structure of wheat alkali lignin after treatment was then characterized by the content of phenolic hydroxyl, infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR). The result showed that comparing with the untreated lignin, the total phenolic hydroxyl content increased after ultrasonic treatment. However, it decreased after laccase treatment. The number of spin decreased by 38% after ultrasonic treatment, but it increased significantly after laccase treatment. Particularly, the number of spin increased by 112% after the single treatment by laccase. Then ultrasonic wave and laccase were applied to treat the sample in sequence. This resulted in the increase of the number of spin by 193%. In these cases, ultrasonic cavitation can induce the demethylation and cleavage of some linkages in lignin. Laccase was able to promote depolymerization. At the same time, phenolic hydroxyl in lignin was oxidized and generated phenoxy radicals for free radical polymerization during the process of laccase-catalyzed oxidation. Small molecule lignin obtained after ultrasonic treatment was prone to react with laccase and C-O was oxidated in this case.

Key words: ultrasonic, laccase, alkali lignin, structural characterization

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