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 CO2 -rich environments (CO2 ) 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 CO2 , respectively. The final pH of kimchi fermented under CC (CC-fermenting) and CO2 (CO2 -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 CO2 -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 CO2 -fermenting kimchi, respectively. Non-lactic acid bacteria were eliminated in fermenting kimchi after 12 days under CC and 6 days under CO2 . I conclude that carbon dioxide can alter bacterial communities, reduce metabolite production, and improve fermented kimchi quality.