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Exploring why sodium lignosulfonate influenced enzymatic hydrolysis efficiency of cellulose from the perspective of substrate–enzyme adsorption

Authors
  • Zheng, Wenqiu1
  • Lan, Tianqing1, 2
  • Li, Hui1
  • Yue, Guojun3
  • Zhou, Haifeng4
  • 1 Kunming University of Science and Technology, 727 South Jingming Rd, Chenggong District, Kunming, 650500, China , Kunming (China)
  • 2 South China University of Technology, No. 381 Wushan Rd, Guangzhou, 510640, China , Guangzhou (China)
  • 3 SDIC Biotech Investment CO., LTD, No. 147 Xizhimen Nanxiao Street, Xicheng District, Beijing, 100034, China , Beijing (China)
  • 4 Shandong University of Science and Technology, Qingdao, 277590, China , Qingdao (China)
Type
Published Article
Journal
Biotechnology for Biofuels
Publisher
Springer (Biomed Central Ltd.)
Publication Date
Jan 30, 2020
Volume
13
Issue
1
Identifiers
DOI: 10.1186/s13068-020-1659-5
Source
Springer Nature
Keywords
License
Green

Abstract

BackgroundCellulase adsorbed on cellulose is productive and helpful to produce reducing sugars in enzymatic hydrolysis of lignocellulose; however, cellulase adsorbed on lignin is non-productive. Increasing productive adsorption of cellulase on cellulose would be beneficial in improving enzymatic hydrolysis. Adding lignin that was more hydrophilic in hydrolysis system could increase productive adsorption and promote hydrolysis. However, the effect mechanism is still worth exploring further. In this study, lignosulfonate (LS), a type of hydrophilic lignin, was used to study its effect on cellulosic hydrolysis.ResultsThe effect of LS on the enzymatic hydrolysis of pure cellulose (Avicel) and lignocellulose [dilute acid (DA) treated sugarcane bagasse (SCB)] was investigated by analyzing enzymatic hydrolysis efficiency, productive and non-productive cellulase adsorptions, zeta potential and particle size distribution of substrates. The result showed that after adding LS, the productive cellulase adsorption on Avicel reduced. Adding LS to Avicel suspension could form the Avicel–LS complexes. The particles were charged more negatively and the average particle size was smaller than Avicel before adding LS. In addition, adding LS to cellulase solution formed the LS–cellulase complexes. For DA-SCB, adding LS decreased the non-productive cellulase adsorption on DA-SCB from 3.92 to 2.99 mg/g lignin and increased the productive adsorption of cellulase on DA-SCB from 2.00 to 3.44 mg/g cellulose. Besides, the addition of LS promoted the formation of LS–lignin complexes and LS–cellulase complexes, and the complexes had more negative charges and smaller average sizes than DA-SCB lignin and cellulase particles before adding LS.ConclusionsIn this study, LS inhibited Avicel’s hydrolysis, but enhanced DA-SCB’s hydrolysis. This stemmed from the fact that LS could bind cellulase and Avicel, and occupied the binding sites of cellulase and Avicel. Thus, a decreased productive adsorption of cellulase on Avicel arose. Regarding DA-SCB, adding LS, which enhanced hydrolysis efficiency of DA-SCB, increased the electrostatic repulsion between DA-SCB lignin and cellulase, and therefore, decreased non-productive adsorption of cellulase on DA-SCB lignin and enhanced productive adsorption of cellulase on DA-SCB cellulose.Graphical abstract

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