Abstract:

Objective  To obtain cholesterol-reducing lactic acid bacteria (LAB) from Tibet kefir,and lay the foundation for physical character and mechanism study of its cholesterol-reducing effect in vitro and in vivo.Methods The cholesterol-reducing ability was tested on 7 strains of lactic acid bacteria isolated from Tibet kefir by the o-phthalaldehyde method.LA1 strain was screened for its better cholesterol-reducing ability,then subjected to physiological and biochemical identification as well as 16S RNA sequencing,and the acid- and oxgall-resistance,growth curve,pH value and antimicrobial activity were studied.Results The strain of LAB (LA1) was obtained,which presented a comparatively high ability of cholesterol reducing.The strain also showed high acid resistance and bile salt tolerance.The time of LA1 entering the logarithm phase of growth and stationary phase of growth was 10 and 18 h after culture.The strain survived for at least 3 h in the MRS broth with pH 1.5 and grew well in the MRS broth containing 0.3% bile salt.The results of bacteria inhibition experiment showed that the separated lactic acid bacterium had remarkable bacteriostasis on the growth of E.coli and Staphylococcus　aureus.The strain was identified to be Lactobacillus acidophilus by 16S rRNA sequencing.Conclusion The isolated LA1 shows probiotic properties of cholesterol reduction,acid and bile tolerance and antimicobial activity.It can be used as primary strain for study on activity in vivo and mechanism.
 

Key words: Tibetan kefir;cholesterol;Lactobacillus acidophilus;16S rRNA