ANTIMUTAGENICITY OF FERMENTED MILK

Reconstituted nonfat dry milk was fermented by Lactobacillus helveticu s CH65, Lactobacillus acidophilus BG2FO4, Streptococcus salivarius ssp . thermophilus CH3, Lactobacillus delbrueckii ssp. bulgaricus 191R, an d by a mixture of the latter two organisms. The fermented milks were t hen freeze-dried, extracted in acetone, dissolved in dimethylsulfoxide , and assayed for antimutagenicity in the Ames test (Salmonella typhim urium TA 100) against N-methyl, N'-nitro, N-nitroso-guanidine, and 3,2 '-dimethyl-4-amino-biphenyl. Dose-dependent activity was significant a gainst both mutagens in all extracts. Maximal inhibitory activity agai nst 3,2'-dimethyl-4-aminobiphenyl and N-methyl, N'-nitro, N-nitroso-gu anidine was 2- and 2.7-fold greater, respectively, than that exhibited by extracts of unfermented milk, Extracts of milk fermented by L. del brueckii ssp. bulgaricus 191R were examined further. Compounds that we re responsible for activity against both mutagens were less soluble in aqueous solutions than in dimethylsulfoxide. Adjustment of milk ferme nted by L. delbrueckii ssp. bulgaricus 191R to pH 3, 7.6, or 13 prior to freeze-drying and acetone extraction did not significantly alter th e activity specific for 3,2'-dimethyl-4-aminobiphenyl. In contrast, co mpounds with activity specific for N-methyl, N'-nitro, N-nitrosoguanid ine were less extractable at pH 7.6. The weak antimutagenicity of unfe rmented milk was not increased by addition of 2% L-lactic acid.