Isolation and identification of the denitrifying bacteria from fermented cabbage (Brassica juncea Coss)

The study was conducted to evaluate the nitrate reduction in fermented mustard cabbage and determine the nitrate level during the fermentation process. A total of 10 samples of fermented mustard cabbage were collected from some retailers at Thu Duc market. The samples were used to determine the nitrate concentration using color compared with sodium salicylate. Then we isolated and cultured the strains of nitrate-reducing bacteria in a specific Giltay medium containing KNO3, as well as testing biochemical characteristics. The cabbage was fermented with additional nitrate-decomposing bacteria and the nitrate concentration was compared with the control treatment. The experimental results showed that the nitrate level of the 10 collected samples of fermented cabbage varied between 2.000 - 5.000mg/kg, exceeding the allowable level of the World Health Organization (WHO), during the three first days of the fermentation. The standard indicators were achieved after 4 and 5 days of the fermentation. In this study, we isolated at least 6 bacterial strains capable of reducing nitrate in a Giltay medium and selected two bacterial strains from others. The results of sequencing, identification and phylogenetic analysis based on NJ method showed that two strains of denitrifying bacteria are Bacillus aryabhattai.