In vitro binding properties towards mutagenic TRP-P1 and antibacterial properties of dadih lactic cultures at frozen temperature storage

Dadih is an Indonesian traditional fermented milk of West Sumatra. Eleven strains of lactic cultures isolated from dadih were screened for their acid and bile acid tolerances. The lactic acid cultures chosen for further experiment were Lactococcus lactis subsp. lactis R-22, Leuconostoc pramesenteroides R-51, Lactobacillus casei subsp. Casei R-52, and Leuconostoc paramesenteroides R-62. The lactic cultures were preserved by freezing at -20 deg. C and -196 deg. C, by different freezing methods, frozen in liquid nitrogen and frozen in dry iceacetone mixture. Low temperature storage such as freezing, may damage the bacterial cell wall. The surviving cells may reveal significant sublethal damage. The aim of this research was to find information about survival rate, and binding properties towards mutagenic Trp-P1 of the preserved lactic acid bacteria from dadih which will provide good information for food industry, especially dairy industry. In general, frozen and stored in liquid nitrogen preserved the lactic cultures better as compared to the other freezing method and frozen storage. Some strains of lactic cultures isolated from dadih possessed probiotic properties such as high viability, galactosidase activity, binding ability towards mutagenic Trp-P1, antipathogenic bacteria, acid tolerance and bile acid tolerance properties frozen and stored in liquid nitrogen for 30 days of Leuconostoc paramesenteroides R-51 cultures in 10 percent sterile non fat dry milk preserved the best as compared to the other lactic cultures as shown by the stability of viability and the least reduced binding properties towards mutagenic Trp-P1. Only Leuconostoc pramesenteroides R-51, Lactobacillus casei subsp. casei R-52 were tolerant to pH 3.5 for 90 min of MRS containing 0.3 percent oxgall at 37 deg. C. Hence, Leuconostoc paramesenteroides R-51 and Lactobacillus casei subsp. casei R-52 have good prospect as probiotic starter cultures. Frozen and stored for 30 days in liquid nitrogen of Leuconostoc paramesenteroides R-51 cultures in 10 percent sterile skim milk preserved the best as compared to the other three lactic cultures as shown by the stability of viability and least reduced binding properties towards mutagenic freeze-injury might be due to cell components other than peptidoglycan, which developed bile sensitivity and seemed to be a mutagen binding receptor