Lactobacillus paracasei HD1.7 used as a starter modulates the bacterial community and metabolome profile during fermentation of Chinese cabbage.

The effects of Lactobacillus paracasei HD1.7 on the bacterial community and metabolome profile during the fermentation of pickled Chinese cabbage (Brassica rapa var. pekinensis) were investigated using high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS). The HD1.7-inoculated samples showed a consistently higher acidity and larger colony forming units until the middle stage of fermentation. The operational taxonomic units and bacterial richness and diversity declined. Lactobacillus was consistently the most abundant followed by Lactococcus, while Lactococcus was initially dominant and then replaced by Lactobacillus in control samples. The HD1.7 starter significantly promoted the growth of more acid-resistant Lactobacillus, inhibited the growth of pathogens and accelerated and enhanced the consumption of free sugars. Eleven categories and 109 kinds of metabolites were identified using GC-MS. Esters and aldehydes were the most abundant categories. Principal component analysis plots showed a similar metabolome shift route but a faster fermentation process due to HD1.7 inoculation. SIGNIFICANCE AND IMPACT OF THE STUDY: Pickled Chinese cabbage is a very traditional and popular food in Asia and where Asians migrate. High-throughput sequencing and GC-MS have been used to investigate the effects of Lactobacillus paracasei HD1.7 as a starter on the bacterial community and metabolome during pickled Chinese cabbage fermentation. Lactobacillus paracasei HD1.7 accelerated acidification and resulted in server acidity. Lactobacillus dominated the entire fermentation process. Lactobacillus paracasei HD1.7-inoculated fermented cabbage had several advantages over naturally fermented cabbage, including a shorter fermentation process, fewer pathogens and more plentiful flavours. This research suggested that L. paracasei HD1.7 would be a desirable starter in the fermentation of other vegetables.