ANTIGENOTOXIC PROPERTIES OF LACTIC-ACID BACTERIA IN THE SALMONELLA-TYPHIMURIUM MUTAGENICITY ASSAY

A high percentage of human tumors is reported to be related to dietary habits. One way to improve the nutritional impact is to increase the intake of protective factors, such as inhibitors of DNA damage and oth er types of anticarcinogens. Specific strains of lactic acid bacteria used to ferment milk are promising candidates that may be antimutageni c and anticarcinogenic. We have studied the antimutagenicity of 10 iso lated strains of beneficial lactic acid bacteria. Four types of fermen ted milk products were also studied for their protective properties. T he effect of these bacteria on the yield of revertants induced by nitr osated beef extract was investigated in the Salmonella typhimurium mut agenicity assay. Eight of 10 isolated Lactobacillus strains reduced th e yield of his+ revertants almost back to the levels of the untreated controls. Different fermented fresh yogurts containing viable bacteria (probably Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus or Lactobacillus acidophilus and Bifidobacteria) showed protective effects as well. The degree of suppressing revertants was i ndependent of the yogurt's fat content. In contrast, yogurt products t hat had been heat treated were not inhibitory. The other fresh ferment ed milk products (e.g., buttermilk, kefir, and ''Dickmilch'') were not antimutagenic in this study. The results imply that some bacteria use d in milk processing have an antimutagenic potential and that this pro perty is specific for the bacterial strain.