In vitro cholesterol-lowering activity of Lactobacillus plantarum and Lactobacillus paracasei strains isolated from the Italian Castelmagno PDO cheese

The discovery of several healthy beneficial effects of the consumption of dairy products fermented with some bacterial strains led to the investigation of the functional properties of these microorganisms. One of the most studied properties is the cholesterol-lowering activity of bacteria with probiotic characteristics, mostly isolated from human gut. In this work, eight Lactobacillus plantarum and five Lactobacillus paracasei strains isolated from cheese were studied in vitro for their cholesterol-lowering action and their acid and bile tolerance. The ability of these strains to remove cholesterol was assessed in de Man, Rogosa and Sharpe (MRS) medium, supplied with cholesterol, and in ultra-high temperature (UHT) whole homogenized milk. Among all tested strains, two L. plantarum and three L. paracasei strains gave rise to a significant reduction of the cholesterol level inMRSbroth; in particular, L. plantarum strains lowered the cholesterol content by an average of 19.4%, whereas L. paracasei strains lowered by an average of 6.8%. The two L. plantarum strains possessing the highest cholesterol-lowering activity in MRS broth were also tested in milk. Results showed that L. plantarum strains maintained this activity because after 24 h the cholesterol decrease ranged from about 5.0% to 8.2% without significant variations between the two strains. Results from the binding assay suggested that cholesterol was mainly removed through the adsorption on the cell wall. Data from acid and bile tolerance assays showed that the L. plantarum dairy isolates were able to maintain viability at pH 2 and to grow in a medium with bile salts, and therefore were regarded as probiotics or dairy starters for new probiotic or functional food production.