Mechanistic Insights into Levilactobacillus brevis JYX2-Mediated Chinese Sauerkraut Fermentation: Nitrite Degradation and Flavor Enhancement

Traditional Chinese sauerkraut production is hindered by prolonged fermentation times, inconsistent quality, and nitrite accumulation during spontaneous fermentation, which collectively hinder industrial scalability. <i>Levilactobacillus brevis</i> JYX2, isolated from traditional fermented sauerkraut, exhibits excellent acid/salt tolerance, alongside distinctive metabolic pathways (for example, heterolactic fermentation, nitrite degradation, etc.), presenting a viable solution to these challenges. This study assessed its ability to improve sauerkraut quality at laboratory and pilot scales. Results indicated that JYX2 inoculation significantly reduced fermentation duration, expedited pH decline, and elevated total acid levels compared to spontaneous fermentation. The nitrite concentration in the inoculated sauerkraut was 0.72 mg/kg (<i>p</i> < 0.05), significantly lower than 1.86 mg/kg in spontaneous group. At pilot scale, nitrite levels further decreased to 0.44-0.70 mg/kg (<i>p</i> < 0.05), which is below the spontaneous group's level of 1.61 mg/kg and approaches the "not detected" threshold (<1 mg/kg). Additionally, inoculation increased total organic acids, particularly lactic acid, and enhanced umami/sweet amino acid proportions. Microbial community analysis showed that JYX2-inoculated groups maintained higher relative abundances of core genera, including Leuconostoc and Latilactobacillus, with Firmicutes as the predominant phylum. Pilot tests confirmed consistent JYX2 performance during scale-up, with uniform quality across sauerkraut layers, showing strong industrial adaptability. In conclusion, JYX2 inoculation shortens fermentation, reduces nitrite levels, enhances flavor, and supports standardized, safe, efficient fermented vegetable production.