Nitrite stress acclimation of Pediococcus pentosaceus improves nitrite degradation in fermented sausages: from...

Nitrite is a widely used additive in processed meat products, but its excessive accumulation raises serious safety concerns due to the formation of carcinogenic N-nitrosamines. Lactic acid bacteria as starter cultures have been explored for nitrite removal, but their efficiency is often limited under nitrite stress. In this study, to improve nitrite degradation performance, stepwise adaptive evolution of Pediococcus pentosaceus (P. pentosaceus) and Leuconostoc mesenteroides (L. mesenteroides) under nitrite stress was conducted followed by nitrite removal test via in vitro and in fermented sausages. Results showed that the acclimated strains of Pediococcus pentosaceus exhibited markedly improved nitrite removal efficiency, achieving near-complete elimination (99.2% removal of 50 mg/L NaNO₂) within 24 h in vitro and significantly accelerated nitrite reduction (77.4% removal of 150 mg/kg NaNO₂ at 7th day) during sausage fermentation compared with the original strains. Microbial community analysis indicated that the adapted culture maintained ecological competitiveness while inhibiting the detrimental Acinetobacter. Transcriptomic profiling between the original and acclimated strains of P. pentosaceus further revealed extensive cellular reprogramming, with differential expression of genes primarily involved in transmembrane transport, energy metabolism, and macromolecular repair. Notably, transport-related systems and ATP synthesis pathways were upregulated, indicating enhanced detoxification capacity and energy supply, whereas nucleotide biosynthesis was suppressed, suggesting strategic resource reallocation under stress conditions. These findings demonstrated that adaptive evolution effectively enhances microbial functionality through coordinated metabolic regulation. This work not only provides mechanistic insights into microbial nitrite metabolism but also offers a feasible strategy for developing safer and more sustainable fermented meat products with reduced additive reliance.