Kimchi starter
Effects of Leuconostoc mesenteroides starter culture on microbial communities and metabolites during kimchi fermentation
Kimchi fermentations usually rely upon the growth of naturally occurring various heterofermentative lactic acid bacteria (LAB), which sometimes makes difficult to produce kimchi with uniform quality. The use of Leuconostoc mesenteroides as a starter has been considered to produce commercial fermented kimchi with uniform and good quality in Korea. In this study, a combination of a barcoded pyrosequencing strategy and a 1H-NMR technique was used to investigate the effects of Leu. mesenteroides strain B1 as a starter culture on kimchi fermentation. Baechu (Chinese cabbage) and Chonggak (radish) kimchi with/without Leu. mesenteroides inoculation were prepared, respectively, and their characteristics including pH, cell numbers, bacterial community, and metabolites were monitored periodically for 40 days. The barcoded pyrosequencing analysis showed that numbers of bacterial operational taxonomic unit (OTU) in starter kimchi decreased more quickly than non-starter kimchi. Members of the genera, Leuconostoc, Lactobacillus, and Weissella were dominant LAB regardless of kimchi type and starter inoculation. Among three the genus Leuconostoc was most abundant, followed by Lactobacillus and Weissella. The use of Leu. mesenteroides as a starter increased Leuconsotoc proportions and decreased Lactobacillus proportions in both kimchi over the kimchi fermentations. However, interestingly, the use of the kimchi starter maintained Weissella proportions of starter kimchi more highly than non-starter kimchi until fermentations finished. The metabolite analysis using the 1H-NMR technique showed that both Baechu and Chonggak kimchi with the starter culture consumed more free sugars more rapidly with more productions of lactic and acetic acids and mannitol, which were well in accordance with the decreases of pH values and the increase of bacterial cell numbers. The PCA strategy using all kimchi componemts including carbohydrates, amino acids, and organic acids also showed that starter kimchi was fermented faster and more. In conclusion, this study showed that kimchi fermentations with the use of Leu. mesenteroides as a starter were completed more rapidly with the more production of kimchi metabolites, which may contribute to produce commercial kimchi with more uniformity and functional properties. And the combination of the barcoded pyrosequencing strategy and the 1H-NMR technique used in this study can monitor microbial succession and their metabolites effectively and will help to understand the relationships between microbial community and metabolite production (taste and function) in diverse fermented foods including kimchi.