Development of an MRS broth-based complete food-grade medium for Lactobacillus gasseri cultivation using food-grade yeast extract and bacteriocins produced by the bacteria
2017
Kasuga, G. (Nihon University, Fujisawa, Kanagawa (Japan). Graduate School of Bioresource Sciences) | Togashi, F. | Abe, M. | Tanaka, M. | Arakawa, K. | Kawai, Y. | Miyamoto, T. | Masuda, T.
Lactobacillus gasseri is one of representative probiotics, and its bacteriocins such as gassericin A (GA) and gassericin T (GT) are expected as beneficial food preservatives. Lb. gasseri poorly grows in milk and normally, MRS broth is used for Lb. gasseri cultivation, however, it is unsuitable for food utilization due to high cost and unauthorized ingredients as food additives. In this study, we aimed at construction of MRS-based food-grade medium (FGM) for Lb. gasseri and production of food-grade bacteriocins. Nine kinds of FGM were prepared by elimination of manganese sulfate from MRS ingredients and replacement of all nitrogen sources to only a food-grade yeast extract (YE: 9 kinds). Then, growth ability of each FGM against Lb. gasseri and other lactobacilli was examined with optical density at 620 nm. All tested strains except one strain of Lb. gasseri were demonstrated the highest growth in 'FR' (YE-FR adding FGM). Furthermore, the optimal conditions of bacteriocin production were determined. GA and GT activity was reached to 246 and 15,754 AU/mL, which was equivalent to one half amount of MRS broth culture supernatant, by optimal 'FR' (GA: 0.9% YE-FR and 0.02% Tween 80; GT: 1.5% and 0.075%) for 24 h at 37degC. This is the first report succeeding on development of the complete food-grade artificial medium for Lb. gasseri. Its lower cost (at least one tenth of MRS broth), enough growth, and high production ability of food-grade bacteriocins of Lb. gasseri show potential of improvement on utilization of Lb. gasseri and its bacteriocins in food industry.
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