Effects of carbon dioxide on metabolite production and bacterial communities during kimchi fermentation.

Bacterial communities and metabolites in kimchi fermented under conventional conditions (CC) compared to CO-rich environments (CO) were analyzed. After a 20-day fermentation, lactic and acetic acid productions were 54 and 69 mM under CC, and 19 and 12 mM under CO, respectively. The final pH of kimchi fermented under CC (CC-fermenting) and CO (CO-fermenting) were 4.1 and 4.7, respectively. For bacterial communities, OTU and Chao1 indices were both 35 in fresh kimchi, 10 and 15 in CC-fermenting kimchi, and 8 and 24 in CO-fermenting kimchi, respectively. Shannon and Simpson indices were 3.47 and 0.93 in fresh kimchi, 1.87-0.06 and 0.46-0.01 in CC-fermenting kimchi, and 1.65-0.44 and 0.63-0.12 in CO-fermenting kimchi, respectively. Non-lactic acid bacteria were eliminated in fermenting kimchi after 12 days under CC and 6 days under CO. I conclude that carbon dioxide can alter bacterial communities, reduce metabolite production, and improve fermented kimchi quality.