Determining the changes in metabolites of Dendrobium officinale juice fermented with starter cultures containing Saccharomycopsis fibuligera FBKL2.8DCJS1 and Lactobacillus paracasei FBKL1.3028 through untargeted metabolomics

Abstract

Abstract Background The present study aimed to investigate the changes in volatile components and metabolites of Dendrobium officinale (D. officinale) juice fermented with starter cultures containing Saccharomycopsis fibuligera and Lactobacillus paracasei at 28 ℃ for 15 days and post-ripened at 4 ℃ for 30 days using untargeted metabolomics of liquid chromatography-mass spectrometry (LC-MS) and headspace solid-phase microextraction-gas chromatography (HS-SPME-GC-MS) before and after fermentation. Results The results showed that the alcohol contents in the S. fibuligera group before fermentation and after fermentation were 444.806 ± 10.310 µg/mL and 510.999 ± 38.431 µg/mL, respectively. While the alcohol content in the fermentation broth group inoculated with the co-culture of L. paracasei + S. fibuligera was 504.758 ± 77.914 µg/mL, with a significant increase in the contents of 3-Methyl-1-butanol, Linalool, Phenylethyl alcohol, and 2-Methyl-1-propanol. Moreover, the Ethyl L (-)-lactate content in the co-culture L. paracasei + S. fibuligera group (7.718 ± 6.668 µg/mL) was higher than those in the L. paracasei (2.798 ± 0.443 µg/mL) and S. fibuligera monoculture groups (0 µg/mL). The co-culture of L. paracasei + S. fibuligera significantly contributed to the metabolic production of ethyl L (-)-lactate in D. officinale juice. The total number of differential metabolites screened after fermentation mainly included alcohols, organic acids, amino acids, nucleic acids, and their derivatives. Of them, twenty-three metabolites were significantly up-regulated in the ten key metabolic pathways of the co-culture L. paracasei + S. fibuligera group, including 11 types of acids. Furthermore, the metabolic pathways, such as pentose and glucuronate interconversions, the biosynthesis of alkaloids derived from terpenoid and polyketide, and aminobenzoate degradation were significantly upregulated in this group. These three metabolic pathways facilitate the synthesis of bioactive substances, such as terpenoids, polyketides, and phenols, and enrich the flavor composition of D. officinale juice. Conclusions The study results demonstrated that the co-culture of L. paracasei + S. fibuligera could promote the flavor harmonization of fermented products, and provide a theoretical basis for the study of the flavor of D. officinale juices and the functional investigation of fermentation metabolites.