Metagenomic analysis of Lactobacillus plantarum DACN768 inoculation effects on volatile flavor compounds, microbial succession, and flavor metabolic network in suansun.

This study analyzed volatile flavor compounds and microbial communities in Lactobacillus plantarum-fermented suansun (LPS), emphasizing the underlying metabolic pathways. A comparison with naturally fermented suansun (NFS) identified 56 volatile flavor compounds in LPS, detected via GC-MS, with levels peaking at 14 days. Alcohols, aldehydes, and esters were the primary components in both NFS and LPS. However, LPS contained significantly more and diverse aldehydes, likely due to L. plantarum's ability to convert free amino acids into aldehydes through the Ehrlich pathway, while keeping phenol levels consistently low. The analysis focused on the ten most abundant bacterial genera in LPS, with Weissella being the most dominant, followed by Lactobacillus, Lactococcus, and Enterococcus. Lactobacillus plantarum exhibited higher metabolic activity and stronger strain interactions compared to NFS. Metagenomic data revealed enhanced carbohydrate and amino acid metabolism in LPS, identifying key pathways contributing to flavor development. Glycolysis and gluconeogenesis, essential for lactic acid bacteria, were active in both LPS and NFS. Pyruvate and propionic acid were major intermediates, while tyrosine was the primary amino acid metabolized in NFS, serving as a main source of aldehydes, alcohols, phenols, and esters. Pyruvate kinase and hexokinase were critical enzymes for the synthesis of alcohols and phenols, primarily mediated by Lactobacillus and Lactococcus. Tyrosine metabolism, specifically through the 4-hydroxyphenylpyruvate and 4-hydroxyphenylacetic acid pathways, was crucial for the formation of phenol and p-cresol. These results offer new insights into the biochemical mechanisms driving flavor formation in suansun.