Lactobacillus plantarum ZJ316 improves the quality of Stachys sieboldii Miq. pickle by inhibiting harmful bacteria growth, degrading nitrite and promoting the gut microbiota health in vitro

Microbial contamination and nitrite accumulation are the two major concerns in the quality control of fermented vegetables. In the present study, a lactic acid bacteria strain Lactobacillus plantarum ZJ316 (ZJ316) was inoculated during Stachys sieboldii Miq. (SSM) fermentation, and the effects of ZJ316 on the quality and bacterial community of SSM during fermentation were investigated. It was observed that ZJ316 could avoid the occurrence of the nitrite peak and maintain the nitrite content of fermented SSM at a low level. Gas chromatography-mass spectrometry (GC-MS) results suggested that ZJ316 gave good flavor to the fermented SSM. 16S rDNA sequencing showed that Firmicutes was the dominant flora after ZJ316 inoculation, and the abundance of Proteobacteria decreased at the same time. At the level of the genus, SSM fermented by ZJ316 had a more obvious inhibitory effect on Pseudomonas on the 7^th day compared with the naturally fermented SSM. Additionally, the effect of ZJ316-fermented SSM on gut microbiota modulation was also evaluated using an in vitro fecal fermentation system. The results revealed that ZJ316 had a relatively subtle influence on intestinal communities with a potentially positive impact on probiotics such as Lactobacillus and Bifidobacterium and a negative impact on Enterobacteriaceae. Furthermore, SSM fermented by ZJ316 promoted the production of short-chain fatty acids (SCFAs) in the human intestine. These results demonstrate that L. plantarum ZJ316 can be used as a good starter in the fermentation process of pickles.