ANTIMUTAGENIC ACTIVITY OF MILK FERMENTED BY STREPTOCOCCUS-THERMOPHILUS AND LACTOBACILLUS-BULGARICUS

Antimutagenic activity of acetone or ethylacetate extracts of skim milk fermented by Streptococcus thermophilus, Lactobacillus bulgaricus, or a combination of both the organisms was studied using Salmonella typhimurium (TA 98 and TA 100). Mutagens used were 4-nitroquinoline-N-oxide (a direct-acting mutagen) and 2-aminofluorene (a mutagen requiring S9 activation). Extracts from all fermented milks showed significant (P < .05) dose response in suppressing the number of revertants caused by NQNO and 2-aminofluorene in both tester strains, whereas extracts from unfermented milk had no effect. Extracts prepared from milk fermented by L. bulgaricus plus S. thermophilus showed significantly (P < .05) more antimutagenic activity than extracts prepared from milk fermented by S. thermophilus alone. Solvent (acetone vs. ethyl acetate) effect was not significant with 4-nitroquinoline-N-oxide as mutagen. However, in the case of 2-aminofluorene, acetone extracts showed significantly (P < .05) higher antimutagenic activity. The results of this and related studies strongly indicate that antimutagenic compounds are produced in milk during fermentation by S. thermophilus and L. bulgaricus.