Lye, Huey Shi
(2013)
In Vitro Cholesterol-Lowering
Mechanisms Of Selected Lactobacillus And
Bifidobacterium Species And Effects Of
Physical Treatment.
PhD thesis, Universiti Sains Malaysia.
Abstract
Fifteen strains of Lactobacillus and Bifidobacterium were screened based on
their adherence property. Lactobacillus acidophilus BT 1088, L. acidophilus FTCC
0291, L. bulgaricus FTCC 0411, L. bulgaricus FTDC 1311, and L. casei BT 1268
showed higher adherence property compared to other strains studied and were thus
selected for examination on cholesterol removal. Cholesterol removal ability was
conducted in vitro, under conditions that mimic the human gastrointestinal tract (pH
8.0). This study provided experimental evidence to strengthen the hypothesis that
lactobacilli could remove cholesterol via different mechanisms, namely assimilation
of cholesterol during growth, binding of cholesterol to cellular surface, disruption of
cholesterol micelle, incorporation of cholesterol into the cellular membrane,
deconjugation of bile salt, bile salt hydrolase (BSH) activity, and conversion of
cholesterol to coprostanol.
Among the mechanisms studied, cholesterol incorporation mechanism was
more prominent and the locations of incorporated cholesterol have also been
identified. Considering that incorporation of cholesterol into the cellular membrane
involves membrane permeability, thus sub-lethal physical treatments such as
ultrasound (20-100 W; 1-3 min), electroporation (2.5-7.5 kV cm-1; 3-4 ms), and UV
radiation (UVA-UVC, 30-90 J m-2) were applied with the objective to further
increase cholesterol removal by Lactobacillus species.
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