Isolation of Bifidobacterium Strains that are Resistant to Human' Stomach Acids and High Bile Salts Concentrations

摘要

Low pH and high bile salts resistant strains of Bifidobacterium were isolated from infant feces and a pharmaceutical product. Strains were first pre-enriched in Raffinose -Bifidobacterium (RB) medium before stressed in an acid (pH3.0) and (1.0 % bile salt (w/ v) ) for 2 hrs each, respectively. Two isolates, designated GB-03 and WN-04, showed considerably high rates of survival when incubated in 50 mM phosphate buffer solution adjusted to pH 2.0 or 3.0; and also in the same buffer solution (pH 6.8) containing oxgall to a final concentration of 0.25, 0.5, 1.0 and 2.0% (w/v). Both isolates were not significant different when tested their survival in these different bile salts concentrations. All strains tested had similar growth rates at pH 4.5. WN-04 displayed high culture stability (log CFU/ml) >9.00 when grown in fresh milk, stored at 4℃, while all others declined to below 8.00.