The production of surfactin during the fermentation of cheonggukjang by potential probiotic Bacillus subtilis CSY191 and the resultant growth suppression of MCF-7 human breast cancer cells

► Bacillus subtilis CSY191 was isolated from Korean soybean paste (doenjang). ► Surfactin identified three isoforms, seven amino acids and hydroxy fatty acids. ► Surfactin inhibited growth of MCF-7 cells (IC50: 10 μg/ml). ► Surfactin contents increased from 0.3 to 48.2 mg/kg during fermentation. ► During fermentation, the anticancer activity increased from 20.29% to 54.66%.