title: Adsorption of Shiga Toxin to Poly-γ-Glutamate Precipitated.
abstract: 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 H2O, 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.
authors: Graduate School of Integrated Arts and Sciences, Tokushima Univ, 1-1 Minamijosanjima-cho, Tokushima, 770-8502, Japan.|Dept. of Science for Human Health, Junior College, Shikoku Univ, 123-1 Ebisuno, Furukawa, Ojin-cho, Tokushima, 771-1192, Japan.
authors: Tsukie
authors: T
authors: Goto
authors: Kobe Women's Junior College, Chuo-ku, Kobe, 650-0046, Japan.
authors: Makiko
authors: M
authors: Tsuji
authors: Graduate School of Integrated Arts and Sciences, Tokushima Univ, 1-1 Minamijosanjima-cho, Tokushima, 770-8502, Japan.
authors: Kaori
authors: K
authors: Kanemaru
authors: Graduate School of Integrated Arts and Sciences, Tokushima Univ, 1-1 Minamijosanjima-cho, Tokushima, 770-8502, Japan.
authors: Kumio
authors: K
authors: Yokoigawa
mesh_terms: D000327:Adsorption; D001412:Bacillus subtilis / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D004043:Dietary Fiber / Q000032:analysis; D019286:Endopeptidase K / Q000378:metabolism; D019453:Escherichia coli O157 / Q000378:metabolism; D005506:Food Contamination; D008970:Molecular Weight; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D022622:Shiga Toxin 1 / Q000737:chemistry*; D022641:Shiga Toxin 2 / Q000737:chemistry*; D014462:Ultrafiltration
chemical_list: D004043:Dietary Fiber; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D019286:Endopeptidase K
keywords: Escherichia coli O157:H7; Shiga toxin; poly-γ-glutamate