Objective  Metabolites generated in the ginseng residue fermentation with Lactiplantibacillus plantarum were analyzed.

Methods Spent residues of ginseng (Codonopsis pilosula) were inoculated with L. plantarum N-25 at low-dose of 1% (Y2), medium-dose of 3% (Y3) or high-dose of 5% (Y4) along with control of no inoculation (Y1). Non-targeted metabolomics was conducted to study the changes in the metabolites, and analyses of differential metabolites and metabolic pathways performed on the solid medium during fermentation.

Results The fermentation raised the number of differential metabolites in the ginseng substrate from 2710 to 2735. Among them, 560 were found commonly existing in all samples, while 128 identified as unique in Y2, 132 in Y3, and 204 in Y4. And 227 metabolites were annotated which included lipids and lipoid molecules (14.54%), phenylpropanoids and polyketide compounds (12.33%), shikimate and phenylpropanoid (11.89%), organic heterocycle compounds (10.13%), biogenic amines and derivatives (8.81%), organic acids and derivatives (8.37%), and fatty acids (7.93%). Contents of some of the substances increased significantly in the fermentation. For instance, flavonoids rose by 1.13 times, lignans by 1.04 times, alkaloids and derivatives by 1.01 times, and organic acids and derivatives by 1.16 times. Of the metabolic pathways, that of isoquinoline alkaloid biosynthesis pathways was the most significantly enriched by the fermentation. The key pathway enhanced by the unique metabolites in Y2 was associated with the cyanogenic amino acid metabolism, while those in Y3 and Y4 with valine, leucine, and isoleucine biosynthesis. The inoculation dosage of L. plantarum N-25 significantly altered the contents and functions of the metabolites generated in the fermentation.

Conclusion The fermentation of C. pilosula residues inoculated with L. plantarum N-25 released functional ingredients such as flavonoids, lignans, alkaloids and derivatives, and organic acids and derivatives. It significantly enriched the pathway of isoquinoline alkaloid biosynthesis.