Isolating High Antimicrobial Ability Lignin From Bamboo Kraft Lignin by Organosolv Fractionation.

Jinyan Yun,Liao Wei,Baishuang Yin,Wei Li,Xiujing Feng,Hongyu Qin,Zhe Ling,Guojiang Li,Peng Wang,Duqiang Gong

doi:10.3389/fbioe.2021.683796

Abstract

Lignin from different biomasses possess biological antioxidation and antimicrobial activities, which depend on the number of functional groups and the molecular weight of lignin. In this work, organosolv fractionation was carried out to prepare the lignin fraction with a suitable structure to tailor excellent biological activities. Gel permeation chromatography (GPC) analysis showed that decreased molecular weight lignin fractions were obtained by sequentially organosolv fractionation with anhydrous acetone, 50% acetone and 37.5% hexanes. Nuclear magnetic resonance (NMR) results indicated that the lignin fractions with lower molecular weight had fewer substructures and a higher phenolic hydroxyl content, which was positively correlated with their antioxidation ability. Both of the original lignin and fractionated lignins possessed the ability to inhibit the growth of Gram-negative bacteria (Escherichia coli and Salmonella) and Gram-positive bacteria (Streptococcus and Staphylococcus aureus) by destroying the cell wall of bacteria in vitro, in which the lignin fraction with the lowest molecular weight and highest phenolic hydroxyl content (L3) showed the best performance. Besides, the L3 lignin showed the ability to ameliorate Escherichia coli-induced diarrhea damages of mice to improve the formation of intestinal contents in vivo. These results imply that a lignin fraction with a tailored structure from bamboo lignin can be used as a novel antimicrobial agent in the biomedical field.

Highlights

Lignin is the most abundant naturally phenolic composition in the cell wall of biomass, which is covalently linked with carbohydrates to form lignin-carbohydrate complexes (LCC) (Huang et al, 2018; Jiang et al, 2018; Dong et al, 2020a)
The kraft lignin from bamboo was fractionated into three fractions (L1, L2, and L3) according to the described protocol in Scheme 1
The lignin fraction with decreased molecular weight and increased phenolic hydroxyl contents could be successfully prepared from bamboo kraft lignin by sequential organosolv fractionation with anhydrous acetone, 50% acetone and 37.5% hexanes

Summary

INTRODUCTION

Lignin is the most abundant naturally phenolic composition in the cell wall of biomass, which is covalently linked with carbohydrates (mainly hemicellulose) to form lignin-carbohydrate complexes (LCC) (Huang et al, 2018; Jiang et al, 2018; Dong et al, 2020a). Anti-oxidation is the main biological activity of lignin, as the hydroxyl groups in lignin endow it with the ability to scavenge the free radicals and reactive oxygen species (ROS) of cells under oxidative stress (Pei et al, 2020; Yu et al, 2020; Gu et al, 2021; Solihat et al, 2021; Zheng L. et al, 2021). Seeking lignin fractions with a sufficient amount of hydroxyl groups from kraft lignin is necessary to improve its antioxidation ability. An industrially feasible organosolv fractionation with different solvents by sequential precipitation was carried out to fractionate kraft lignin into the sample with low molecular weight and high functional groups content, which aimed to improve its antimicrobial activities for bacteria. The diarrheal mice model induced by E. coli were fed with a lignin fraction with the best antioxidant activity to evaluate its antimicrobial ability in vivo

MATERIALS AND METHODS

RESULTS AND DISCUSSION

SUMMARY

ETHICS STATEMENT