In Vitro Binding of Mutagenic Pyrolyzates to Lactic Acid Bacterial Cells in Human Gastric Juice

¹ Laboratory for Microbial Biochemistry, Faculty of Applied Biological Science, Hiroshima University, Higashi-Hiroshima 724, Japan

The binding of mutagenic pyrolyzates to freeze-dried cells of Streptococcus cremoris Z-25 was investigated in human gastric juice and compared with the ability of these pyrolyzates to bind in distilled water pH 6.30). The pH of donated gastric juice ranged from 1.2 to 7.8. Binding that occurred in gastric juice was pH dependent, and binding was affected by NaCl, CaCl₂, and MgCl₂. Less of Trp-P-2 was bound in gastric juice at low pH (1.2, 1.48, and 2.1) than at pH 4 to 8. The strain bound simultaneously Trp-P-1, Trp-P-2, and Glu-P-1. The maximum amounts of Trp-P-2 bound to S. cremoris Z-25 were approximately 47.50 µg/mg of cells. Freeze-dried cells treated at 120°C for 15 min or 80°C for 3 h showed increased binding of Trp-P-2. However, binding decreased 10% after heating at 120°C for 15 min. Cells nonthermally killed by gastric juice (pH 1.5) had the same Trp-P-2 binding capacity as viable cells. Lactobacillus acidophilus IFO 13951 and Bifidobacterium bifidum IFO 14252 representation of the intestinal bacteria nonthermally killed by gastric juice also showed larger binding of Trp-2.

Key Words: binding • human gastric • juice • mutagenic pyrolyzates

Submitted on April 26, 1990
Accepted on September 24, 1990

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