Bacteriocin Production by Enterococcus faecalis TS9S17 in MRS Medium with Tuna Condensate as a Nitrogen Source and Its Characteristics

The purpose of this study was to optimize bacteriocin production by Enterococcus faecalis TS9S17 isolated from a mangrove forest. Ent. faecalils TS9S17 produced 40 AU/ml bacteriocin in MRS medium at an initial pH of 6.5 and at 37 °C for 24 h, which inhibited Lactobacillus sakei subsp. sakei JCM 1157 and Listeria monacytogenes . When 26.5 g/l of tuna condensate was used instead of peptone, beef extract, and yeast extract in the MRS medium, Ent. faecalils TS9S17 also produced 40 AU/ml of bacteriocin. The maximum bacteriocin activity, 160 AU/ml, was obtained at pH 6.5 and at 25 °C. Crude bacteriocin displayed the highest activity at pH 6 and remained active over a wide pH range. It was active after heating at 60 °C for 60 min, but showed little activity after heating at 121 °C for 15 min. It could be kept at -20 °C for more than 4 weeks. This study shows that tuna condensate could be used as a low cost nitrogen source for bacteriocin production.