Thermal treatment of alkali lignin to eliminate its inhibition of pancreatic proteases in vitro

Jian Zhu; Long Yu; Regine Stockmann; Hongsheng Liu; Wei Zou

doi:10.1016/j.foodchem.2024.138412

Thermal treatment of alkali lignin to eliminate its inhibition of pancreatic proteases in vitro

Food Chem. 2024 Jun 1:442:138412. doi: 10.1016/j.foodchem.2024.138412. Epub 2024 Jan 19.

Authors

Jian Zhu¹, Long Yu², Regine Stockmann³, Hongsheng Liu⁴, Wei Zou⁵

Affiliations

¹ School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China.
² School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China; Sino-Singapore International Joint Research Institute, Knowledge City, Guangzhou 510663, China.
³ CSIRO Agriculture and Food, Werribee, VIC 3030, Australia.
⁴ School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China; Sino-Singapore International Joint Research Institute, Knowledge City, Guangzhou 510663, China. Electronic address: liuhongsheng@scut.edu.cn.
⁵ CSIRO Agriculture and Food, Werribee, VIC 3030, Australia. Electronic address: wei.zou@uq.net.au.

PMID: 38241996
DOI: 10.1016/j.foodchem.2024.138412

Abstract

This study aims to investigate how alkali lignin inhibits protein digestion and explore thermal treatment as a potential solution. Solid alkali lignin species pre-heated at different temperatures (150, 200, and 250 °C) and soluble acid-differentiated fractions are subjected to in vitro protein digestion. A range of techniques, including Thermogravimetric Analysis (TGA), Size-Exclusion Chromatography (SEC), Zeta Potential Analyzer, ¹H NMR, Isothermal Titration Calorimetry (ITC), and Molecular Docking, were used to investigate the inhibitory mechanism of alkali lignin on pancreatic proteases hydrolysis. Our results suggest that soluble alkali lignin inhibits pancreatic trypsin and chymotrypsin, with the acid-differentiated soluble fraction (Lg_pH<1) displaying the strongest inhibition and proteases' binding affinity due to the abundance of polar groups (e.g., -OH, -CHO), which facilitate hydrogen-bond formation. Furthermore, pre-heating lignin (200 °C) was confirmed effective for removing Lg_pH<1 and its negative nutritional influence, providing a feasible strategy for overcoming the negative impact of alkali lignin on protein digestion.

Keywords: Alkali lignin; Chymotrypsin; Enzymatic inhibition; In vitro protein digestion; Trypsin.

MeSH terms

Acids
Alkalies* / chemistry
Chymotrypsin
Hydrolysis
Lignin* / metabolism
Molecular Docking Simulation

Substances

Lignin
Alkalies
Acids
Chymotrypsin