Goto, Tsukie Tokushima University|Shikoku University
Tsuji, Makiko Kobe Women's Junior College
Escherichia coli O157:H7
We screened foods containing indigestible ingredients in the ability to adsorb Shiga toxin (Stx). When 5 mg of foods and dietary ﬁbers such as dry vegetables and inulin were mixed and incubated with 0.5 mL of Stx solution (100 ng/mL) containing 0.5% bovine serum albumin, both Stx1 and Stx2 seemed to be adsorbed by only a fermented food, natto (a traditional Japanese food prepared from steamed soybeans by the biological action of Bacillus subtilis). We puriﬁed the Stx-adsorbing substance from natto by extraction with H 2 O, acid treatment, Proteinase K treatment, and an ion exchange chromatography. The puriﬁed substance showed an average molecular mass of about 600 kDa. We identiﬁed it as poly-γ -glutamate (PGA) by amino acid analysis of its hydrolysate and peptide analysis after its treatment with Proteinase K. Puriﬁed PGA (MW: molecular weight = about 600 kDa) was considered to adsorb both Stx1 and Stx2 when we separated adsorbed and unadsorbed Stxs (MW = about 72 kDa) by an ultraﬁltration method with a centrifugal ﬁlter unit (MWCO: molecular weight cut-off = 100 K). However, PGA with the ability to adsorb Stx was an insoluble form precipitated in the ﬁlter unit during centrifugation. PGA precipitated beyond the saturated density was also conﬁrmed to well adsorb both Stx1 and Stx2 by an equilibrated dialysis method. To the best of our knowledge, this is the 1st report on food-adsorbing Stx.
Journal of Food Science
©2016 Institute of Food Technologists®
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