Study on differences in the enzyme hydrolysis induced from lignins from diverse types of lignocellulosic biomass

ABSTRACT

The content and composition of substrate lignin significantly impacted the enzymatic hydrolysis of the lignocellulosic biomass process, mainly manifested in steric hindrance and non-productive adsorption, which was considered one of the main obstacles affecting enzymatic hydrolysis. Because of the intricate lignin structure, the mechanism of its effect on enzyme hydrolysis was unclear. Hence, this study aimed to inquire into the effect of the lignin structural units on the enzymatic hydrolysis of lignocellulosic biomass. Lignins with different structural units were isolated from non-wood: reed, rice straw, and bamboo. Analyzed the structural differences of lignins using methods like GPC, FT-IR, and NBO. The results showed that bamboo lignins had a higher S/G ratio of 1.7: 1, which was different from reed and rice straw lignin of 0.9: 1. The surface morphology of lignin/cellulose composite films was characterized byAFM. QCM-D was used to monitor the hydrolysis process of lignin/cellulose composite films in situ and in real-time. Bamboo lignin composite film had the slowest enzymatic hydrolysis rate of 0.2 min⁻¹, the longest time (23.6 min) to get the maximum enzymatic hydrolysis, and the lowest maximum hydrolysis frequency of 83.9 Hz. Structural analysis indicated the bamboo lignin had a higher yield of the content of syringyl unit, a higher degree of non-condensation, and contained more aryl ether bonds. Both enzymatic hydrolysis and QCM-D results showed that bamboo had the lowest enzymatic hydrolysis efficiency. This study focuses on how the structural differences of the three isolated lignins affect the enzymatic hydrolysis process. It suggests that the lignin with a higher S/G ratio inhibits the enzyme adsorption to cellulose present in composite and retard enzymatic hydrolysis process of cellulose more obviously.

KEYWORDS:

• Lignocellulosic biomass
• lignin
• structural unit
• QCM-D
• enzymatic hydrolysis

Acknowledgments

We are grateful for the financial support from the National Natural Science Foundation of China (grant numbers 31730106, 32271797).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available on request to the Corresponding author.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [31730106, 32271797]

Notes on contributors

Chunyang Zou

Chunyang Zou graduated from the Changshu Institute of Technology with a bachelor's degree in 2018. He had been studying for a master's degree at the College of Light Industry and Food Science of Nanjing Forestry University under the supervision of Prof. Wenjuan Wu and graduated in 2021. His project mainly focuses on exploring the structure of lignin and its effect on enzymatic hydrolysis.

Jiaquan Li

Jiaquan Li is currently studying light industry and food at Nanjing Forestry University. He loves to explore and is particularly interested in lignin utilization. He hopes to make some changes through his own efforts.

Wenjuan Wu

Wenjuan Wu received her Dr. Ing. degree in pulp and paper from Nanjing Forestry University in 2015. She went to the University of Tokyo to study abroad during her Ph.D. Her research interests are biomass resources chemistry and engineering, including modification and application of natural polymer materials, clean separation and molecular structure of lignocellulose cell wall components, and interaction of biological macromolecules and their influence on biomass conversion.