National Agricultural Research Center for Kyushu Okinawa Region
Abstract
The antibacterial activity of sweetpotato fiber against pathogenic Escherichia coli (O157:H7), Salmonella typhimurium, Staphylococcus aureus, and Saccharomyces cerevisiae was investigated using microcalorimetry. The fiber enzymatically prepared from three varieties of sweetpotato storage roots (Koganesengan, Shiroyutaka, and Kyushu No. 124) exhibited bacteriostatic activity against pathogenic E. coli, S. typhimurium, and S. aureus; however, commercial fiber (Satsumaimo fiber) after citric acid fermentation of sweetpotato starch waste did not exhibit antibacterial activity against these bacteria. All sweetpotato fiber, including Satsumaimo fiber, used in this experiment exhibited no antibacterial activity against S. cerevisiae. Chitin exhibited no activity against pathogenic E. coli; however, clear activity of pectin, calcium alginate, and Kyushu No. 124 was observed, in that order. The yield of boiled-water extract from enzymatically prepared fiber was three times greater than that from Satsumaimo fiber. Chemical analysis of the boiled-water-soluble fraction suggested that its main component is pectin. The acid sugar content of sweetpotato fiber was much higher than that of Satsumaimo fiber. The boiled-water-insoluble fraction exhibited bacteriostatic activities, but the boiled-water-soluble fraction did not. Bacteriostatic activity of sweetpotato fiber was suggested to be due to the synergistic effect of cellulose, hemicellulose, and pectin of the fiber
