Bacteriocins are natural antibacterial peptides ribosomally biosynthesized by bacteria. Gassericin T which is a bacteriocin produced by many strains of Lactobacillus gasseri has a broad antibacterial spectrum against food spoilage and pathogenic Gram-positive bacteria; therefore, the bacteriocin and its producers are predicted for use as safe food preservatives. However, probiotic Lb. gasseri strains show poor growth and minimally produce gassericin T in food-grade
natural media such as reconstituted cheese whey, unlike in MRS broth. The growth of Lb. gasseri in reconstituted cheese whey was improved by adding proteose peptone as a nutrient factor. The production of gassericin T in MRS broth was specifically inhibited by adding divalent metal cations, and then the inhibition was removed using a chelator of divalent cations, trisodium citrate dihydrate. The production of gassericin T in reconstituted cheese whey was also restored by adding trisodium citrate dihydrate, and the activity was enhanced by a surfactant, Tween 80. In addition, trisodium citrate dihydrate led to over-production of and synergistic antibacterial effect with gassericin T. In this study, we developed a cheese whey-based medium containing proteose peptone, trisodium citrate dihydrate and Tween 80 for gassericin T production. The developed food-grade medium may contribute to the effective use of some bacteriocins from probiotic lactic acid bacteria for biopreservation of foods.