A comparative study on flaxseed lignan biotransformation through resting cell catalysis and microbial fermentation by β‐glucosidase production Lactiplantibacillus plantarum

Abstract BACKGROUND Flax lignan has attracted much attention because of its potential bioactivities. However, the bioavailability of secoisolariciresinol diglucoside (SDG), the main lignan in flaxseed, depends on the bioconversion by the colon bacteria. Lactic acid bacteria (LAB) with β ‐glucosidase activity has found wide application in preparing bioactive aglycone. RESULTS LAB strains with good β ‐glucosidase activity were isolated from fermented tofu. Their bioconversion of flax lignan extract was investigated by resting cell catalysis and microbial fermentation, and the metabolism of SDG by Lactiplantibacillus plantarum C5 following fermentation was characterized by widely targeted metabolomics. Five L. plantarum strains producing β ‐glucosidase with broad substrate specificity were isolated and identified, and they all can transform SDG into secoisolariciresinol (SECO). L. plantarum C5 resting cell reached a maximum SDG conversion of 49.19 ± 3.75%, and SECO generation of 21.49 ± 1.32% (0.215 ± 0.013 m m ) at an SDG substrate concentration of 1 mM and 0.477 ± 0.003 m m SECO was produced at 4 m m within 24 h. Although sixteen flax lignan metabolites were identified following the fermentation of SDG extract by L. plantarum C5, among them, four were produced following the fermentation: SECO, demethyl‐SECO, demethyl‐dehydroxy‐SECO and isolariciresinol. Moreover, seven lignans increased significantly. CONCLUSION Fermentation significantly increased the profile and level of flax lignan metabolites, and the resting cell catalysis benefits from higher bioconversion efficiency and more straightforward product separation. Resting cell catalysis and microbial fermentation of flax lignan extract by the isolated β ‐glucosidase production L. plantarum could be potentially applied in preparing flax lignan ingredients and fermented flaxseed. © 2024 Society of Chemical Industry.