Inoculation With Pediococcus pentosaceus Alters Microbial Interactions, Metabolic Landscapes, and Quality Traits in Spontaneously Fermented Carrot Pickles.

Abstract

Spontaneous carrot pickling often results in inconsistent product quality, prolonged fermentation, and potential safety risks due to the uncontrolled activity of indigenous microbiota. In this study, Pediococcus pentosaceus CLB16, exhibiting potential for acid and salt tolerance and antibacterial activity, was evaluated as a starter culture for carrot pickle fermentation. Inoculation with CLB16 significantly decreased pH, increased lactic acid production, and reduced nitrite levels compared with natural fermentation. The inoculated group also showed better color retention, moderate and controlled tissue softening, and improved overall texture, relative to the NF group. High-throughput sequencing revealed that CLB16 reshaped the bacterial community, shifting its dominance from indigenous Lentilactobacillus and Limosilactobacillus to a Pediococcus-dominated consortium. Notably, microbial community assembly shifted from predominantly deterministic to stochastic processes following inoculation. Network analysis further revealed strengthened microbial interactions, characterized by increased numbers of nodes and edges and a higher proportion of positive correlations. GC-IMS and ¹H-NMR identified 11 differential volatile compounds and 30 differential non-volatile metabolites between the NF and InPp groups. CLB16 inoculation promoted the formation of esters and terpenes while suppressing aldehydes associated with off-flavors. KEGG enrichment analysis indicated substantial alterations in carbohydrate and amino acid metabolism, particularly glycolysis/gluconeogenesis and valine, leucine, and isoleucine biosynthesis. Correlation analysis identified Pediococcus as a central microbial driver, positively associated with organic acids, flavor-active esters, and improved texture, but negatively associated with nitrite accumulation and pH. Collectively, these findings demonstrate the strong potential of CLB16 as an industrial starter culture for fermented vegetables.