Cholesterol Assimilation of Two Probiotic Strains of Lactobacillus casei used as Dairy Starter Cultures

Background and Objective: Consumption of milks fermented with lactic acid bacteria has been shown to improve lipid profiles; however, the mechanisms underlying this improvement are not clear. Using in vitro analyses, the aim of this study was to investigate how Lactobacillus casei strains AP and AG assimilate cholesterol. Material and Methods: Bacterial growth in ox gall-supplemented media, quantity of assimilated cholesterol and activity of bile salt hydrolase were assessed in Lactobacillus casei strains AP and AG. Furthermore, cholesterol attachment to cell walls was assessed using scanning electron microscopy. Results and Conclusion: Lactobacillus casei AG showed a higher cholesterol assimilation (13.05 mg dl-1 ±0.48) than Lactobacillus casei AP (8.05 mg dl-1 ±0.48) as well as a faster growth rate of the former strain that that of the latter one. Growth inhibition of Lactobacillus casei AP was associated with increased activity of bile salt hydrolase (halo size of 1.62 mm ±0.20), compared to that of Lactobacillus casei AG (1.37 mm ±0.07) and upregulation of the bsh gene. High cholesterol assimilations by Lactobacillus casei AG seem to attribute to membrane attachment via resistance to bile acids.