Limosilactobacillus fermentum CGMCC 1.7434 and Debaryomyces hansenii GDMCC 2.149 synergize with ultrasound treatment to efficiently degrade nitrite in air-dried ducks

Nitrites in meat products are important food additives with coloring, antibacterial and antioxidant effects, but excessive intake of nitrites can pose health risks, including an increased risk of cancer due to the formation of carcinogenic nitrosamines. In the present study, Limosilactobacillus fermentum CGMCC 1.7434 was screened and the effects of it and Debaryomyces hansenii GDMCC 2.149 and their combination on nitrite degradation were investigated. It was found that the co-culture of L. fermentum CGMCC 1.7434 and D. hansenii GDMCC 2.149 significantly enhanced nitrite degradation (99.58%). The findings on salt and ethanol tolerance suggest suitability for application in meat fermentation processes. Scanning electron microscopy and additional data indicate that D. hansenii GDMCC 2.149 facilitates the growth, acid production, adhesion, secretion of AI-2 signaling molecules, and biofilm formation of L. fermentum CGMCC 1.7434. Metabolomics analysis suggests that these microorganisms reduce nitrite levels by converting NH₃ derived from nitrite into L-glutamine, which is further transformed into N-nitroso compounds and their downstream derivatives through the ABC transporter pathway, the TCA cycle, and the amino acid metabolism pathway. Microbial community analyses showed that L. fermentum CGMCC 1.7434 and D. hansenii GDMCC 2.149 were successfully inoculated into air-dried ducks, becoming dominant strains and effectively inhibiting the growth of pathogenic bacteria. Furthermore, during the processing of air-dried duck, the combination of ultrasonic cavitation (250 W, 4 min, 30°C, 40 kHz) with the co-fermentation of L. fermentum CGMCC 1.7434 and D. hansenii GDMCC 2.149 effectively reduced nitrite content (84.55%) and TVB-N levels in the meat, without compromising color or TBARS values. This is crucial for understanding the mechanism of nitrite degradation by LAB in synergy with yeast and for the advancement of low-nitrite air-dried duck products.