Effect and potential mechanism of nitrite reductase B on nitrite degradation by Limosilactobacillus fermentum RC4

Qing Fan; Chaoran Xia; Xiaoqun Zeng; Zhen Wu; Yuxing Guo; Qiwei Du; Maolin Tu; Xinanbei Liu; Daodong Pan

doi:10.1016/j.crfs.2024.100749

Effect and potential mechanism of nitrite reductase B on nitrite degradation by Limosilactobacillus fermentum RC4

Curr Res Food Sci. 2024 Apr 24:8:100749. doi: 10.1016/j.crfs.2024.100749. eCollection 2024.

Authors

Qing Fan^{1

2

3}, Chaoran Xia^{1

2

3}, Xiaoqun Zeng^{1

2

3}, Zhen Wu^{1

2

3}, Yuxing Guo^{1

4}, Qiwei Du^{1

2

3}, Maolin Tu^{1

2

3}, Xinanbei Liu⁵, Daodong Pan^{1

2

3}

Affiliations

¹ State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Ningbo University, Ningbo, China.
² Key Laboratory of Animal Protein Food Processing Technology of Zhejiang Province, College of Food Science and Engineering, Ningbo University, Ningbo, China.
³ Zhejiang-Malaysia Joint Research Laboratory for Agricultural Product Processing and Nutrition, Ningbo University, Ningbo, China.
⁴ School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China.
⁵ College of Resources and Environment, Baoshan University, Baoshan, China.

Abstract

Nitrite has the potential risk of hypoxic poisoning or cancer in pickled food. In our previous study, Limosilactobacillus fermentum (L. fermentum) RC4 is effective in nitrite degradation by producing nitrite reductase B (NirB). To investigate the detailed mechanism from the genome, response, and regulation of NirB, the whole-genome sequence of L. fermentum RC4 was analyzed, the L. fermentum-EGFP-nirB with enhanced green fluorescent protein (EGFP) labeled the nitrite reductase large subunit nirB, and the recombined L. fermentum-NirB with overexpression NirB strain was conducted. The key genes within the dominant metabolism pathways may be involved in stress tolerance to regulate the degrading process. The green fluorescence density of EGFP indicated that NirB activity has a threshold and peaked under 300 mg/L nitrite concentration. NirB overexpressed in L. fermentum RC4 boosted the enzyme activity by 39.6% and the degradation rate by 10.5%, when fermented in 300 mg/L for 40 h, compared to the control group. RNA-seq detected 248 differential genes mainly enriched in carbohydrate, amino acid, and energy metabolism. The ackA gene for pyruvate metabolism and the mtnN gene for cysteine metabolism were up-regulated. NirB regulates these genes to produce acid and improve stress resistance for L. fermentum RC4 to accelerate nitrite degradation.

Keywords: Limosilactobacillus fermentum RC4; Nitrite degradation; Nitrite reductase; Whole-genome sequence; nirB gene.