Identification of Lactobacillus strains from breast-fed infant and investigation of their cholesterol-reducing effects

Abstract

Hypercholesterolemia has been reported to be the main cause of cardiovascular diseases and the leading cause of death. Therefore, decreasing serum cholesterol level is very important for preventing the cardiovascular diseases. It has been supposed that probiotics in human gastrointestinal tract have the ability to decrease serum cholesterol level by reducing the absorption of cholesterol from the intestinal tract and the bile salt deconjugation. In this study, 28 strains of Lactobacillus spp., isolated from breast-fed infant's feces, were identified and investigated for their bile salt deconjugation ability. The deconjugation ability of the strains was determined by the release of cholic acid resulting from the deconjugation of conjugated bile salts. Research results showed that four of the strains had bile salt deconjugation ability. The strains with deconjugation ability have been identified in species level by using biochemical test, and molecular techniques, API 50CHL test and 16S rRNA gene sequence analysis respectively. LP1, E3, and E9 strains with deconjugation activity were identified as Lactobacillus rhamnosus and GD2 strain as Lactobacillus plantarum. Even if oxgall decreases the viability of bacteria, the highest amount of cholesterol precipitation (42%) was performed by GD2 strain in the presence of 0.3% (w/v) bile. This study demonstrated that the identified Lactobacillus strains had an excellent ability to survive at low pH, a high bile deconjugation ability, and hypocholesterolemic effect in in vitro conditions.

Bile salt deconjugation activity of Propionibacterium strains and their cholesterol co‐precipitation abilities

“…Each medium was inoculated separately with Propionibacterium spp. strains at 2% (v/v) level and incubated anaerobically at 30 °C for 48 h. The analysis for the free cholic acid that was released during deconjugation was carried out according to the method of Yıldız et al (). Briefly, 10 mL culture of each strain after the incubation period was adjusted to pH 7.0 with 1 N NaOH.…”

“…Freshly autoclaved YEL broths were supplemented with oxgall as the source of bile salts (Sigma Farma). Water‐soluble cholesterol (polyoxyethanyl‐cholesteryl sebacate; Sigma) was used as previously described (Yıldız et al ). To imitate approximate intestinal tract conditions, different bile acid concentrations were used as 0.0, 0.06, 0.15 and 0.30% (w/v) oxgall (Öner et al ).…”

“…Cholesterol solution (10 mg/mL) was filtered to be sterilised and added to the medium until a final cholesterol concentration of 100 μg/mL. All the media were inoculated with 2% (v/v) level of each strain and incubated anaerobically at 30 °C for 48 h. Following the incubation, bacterial cells were centrifuged (at 50 000 g for 20 min at 4 °C), and residual cholesterol concentration in the spent broth was detected with the method described by Yıldız et al (), with a slight modification. 0.5 mL of the supernatant and 3 mL of 95% ethanol were added to the samples and vortexed for 1 min.…”

Effects of supplementing lactic acid bacteria on fecal microbiota, total cholesterol, triglycerides and bile acids in rats.

“…Hyper cholesterol associated with cardiovascular disease is one of the most important causes of death (Yıldız, Öztürk andAslım 2011, Zhang et al 2012). Elevated serum cholesterol level is a risk factor for ischemic heart disease and other lethal disease (Watanabe et al 2013).…”

“…LAB have a long history of use in human foods and are naturally present among human gut flora (Szabo et al 2011). Live microbial feed supplements beneficially affect the host by improving its intestinal microbial balance (Yıldız et al 2011, Lim 2009). Probiotics (LAB) are normal components of the intestinal micro flora in both humans and animals.…”