Quality improvement of fermented chili pepper by inoculation of Pediococcus ethanolidurans M1117: Insight into relevance of bacterial community succession and metabolic profile

Pediococcus species have been found as the dominant microorganism in a low temperature fermented Sichuan paocai, whereas their role in quality formation remains unclear. In this work, the chili pepper fermented with P. ethanolidurans M1117 (PFP) was compared with that fermented spontaneously (SFP). We noticed that inoculation of P. ethanolidurans M1117 can decrease salinity, pH, nitrite and capsaicinoids, protect pepper's color and texture, and increase sourness and sweetness. Metabolomic analysis showed that esters and terpenes which are the main aroma compounds in PFP group were more plentiful than those in SFP. Furthermore, correlation analysis between microbiota and flavors demonstrated that most metabolites in glycolysis/gluconeogenesis, citrate cycle and biosynthesis of terpenoids and steroids were positively correlated with P. ethanolidurans, which probably played a vital role in the formation of special flavor and taste. These findings suggested that inoculation of P. ethanolidurans M1117 can enhance the sensory quality of fermented chili pepper, and the strain is expected to be a starter for Sichuan pickle fermentation.