Relationships Between Bacterial Flora and Growth and Decline of Nitrite During Fermentation of Northeast Sauerkraut
To investigate the relationship between bacterial flora and growth and decline of nitrite during fermentation of northeast sauerkraut,in this experiment,two closed fermentation systems are set up,namely,nitrite is not added(natural fermentation group)and nitrite is added(control group).In combination with the main physicochemical indexes(nitrite,pH value and so on),the bacterial species in the fermentation broth of sauerkraut at different fermentation stages(relative abundance ranking top 30)in the two systems are compared and analyzed.In this experiment,the changes of the bacterial flora of samples with and without nitrite at different fermentation stages are investigated.The results show that the addition of nitrite has an effect on the growth of bacteria throughout the fermentation cycle,and that nitrite makes the relative abundance of the dominant Lactobacillus genera(Lactococcus,Leuconostoc,Lactobacillus),α-Proteus(Allorhizobium-Neorhizobium-Parararhizobium-Rhizobium,Aureimonas,Brevundimonas,Methylobacterium,Sphingomonas),β-Proteus(Acidovorax,Aquabacterium,Comamonas,Delftia,Herbaspirillum,Methylophilus,Methylovorus),CFB genera(Dyadobacter,Pedobacter,Sphingobacterium)and uncultured genera(Brassica_napus_rape,uncultured_bacterium_f_Chitinophagaceae,uncultured_bacterium_f_env.OPS_17,uncultured_bacterium_o_Chloroplast)increase in the early stages of fermentation;and it makes the relative abundance of pathogenic bacteria genera(Acinetobacter,Alkanindiges,Chryseobacterium,Enterococcus,Serratia,uncultured_bacterium_f_Burkholderiaceae,uncultured_bacterium_f_Enterobacteriaceae,uncultured_bacterium_f_Xanthobacteraceae)always stay in a low-level state.In the S system,the early stage of fermentation is the nitrite accumulation stage.At this time,Lactococcus and Leuconostoc are the dominant Lactobacillus,and Lactobacillus becomes the absolute dominant Lactobacillus at the middle and late stages of fermentation.In the early stage of fermentation,the pathogenic bacteria such as Acinetobacter,Enterococcus,Serratia and uncultured_bacterium_f_Enterobacteriaceae proliferates largely,leading to a large accumulation of nitrite,and the accumulated nitrite keeps the relative abundance of these pathogenic bacteria always at a low-level state,with the most significant effect on the growth of Serratia.
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